Reverse String characters in java

Reverse String characters in java - java

Am trying to reverse a string using a method in java, I can fetch all the elements of the string and print them out in order via a loop, my problem is reversing the string such that the first comes last and the last comes first, I tried to find a reverse function to no avail... Here is what I have so far...
private static void palindrome() {
char[] name = new char[]{};
String name1;
System.out.println("Enter your name");
Scanner tim = new Scanner(System.in);
name1 = tim.next();
int len = name1.length();
for (int i = 0; i <= len; ++i) {
char b = name1.charAt(i);
System.out.println(b + " ");
}
}
That loop succeeds in printing out the single characters from the string.

You can use StringBuilder like this:
import java.lang.*;
import java.io.*;
import java.util.*;
class ReverseString {
public static void main(String[] args) {
String input = "Geeks for Geeks";
StringBuilder input1 = new StringBuilder();
// append a string into StringBuilder input1
input1.append(input);
// reverse StringBuilder input1
input1 = input1.reverse();
// print reversed String
System.out.println(input1);
}
}
You can also modify your code to do this:
1 -
for (int i = 0; i <= len; ++i) {
char b = name1[len - i];
System.out.println(b + " ");
}
2 -
for (int i = len; i >= 0; --i) {
char b = name1.charAt(i);
System.out.println(b + " ");
}

Using Java 9 codePoints stream you can reverse a string as follows. This example shows the reversal of a string containing surrogate pairs. It works with regular characters as well.
String str = "𝕙𝕖𝕝𝕝𝕠 𝕨𝕠𝕣𝕝𝕕";
String reversed = str.codePoints()
// Stream<String>
.mapToObj(Character::toString)
// concatenate in reverse order
.reduce((a, b) -> b + a)
.get();
System.out.println(reversed); // 𝕕𝕝𝕣𝕠𝕨 𝕠𝕝𝕝𝕖𝕙
See also: Reverse string printing method

You simply need to loop through the array backwards:
for (int i = len - 1; i >= 0; i--) {
char b = name1.charAt(i);
System.out.println(b + " ");
}
You start at the last element which has its index at the position length - 1 and iterate down to the first element (with index zero).
This concept is not specific to Java and also applies to other data structures that provide index based access (such as lists).

Use the built-in reverse() method of the StringBuilder class.
private static void palindrome() {
String name1;
StringBuilder input = new StringBuilder();
System.out.println("Enter your name");
Scanner tim = new Scanner(System.in);
name1 = tim.next();
input.append(name1);
input.reverse();
System.out.println(input);
}

Added reverse() function for your understanding
import java.util.Scanner;
public class P3 {
public static void main(String[] args) {
palindrome();
}
private static void palindrome() {
char[] name = new char[]{};
String name1;
System.out.println("Enter your name");
Scanner tim = new Scanner(System.in);
name1 = tim.next();
String nameReversed = reverse(name1);
int len = name1.length();
for (int i = 0; i < len; ++i) {
char b = name1.charAt(i);
System.out.println(b + " ");
}
}
private static String reverse(String name1) {
char[] arr = name1.toCharArray();
int left = 0, right = arr.length - 1;
while (left < right) {
//swap characters first and last positions
char temp = arr[left];
arr[left++] = arr[right];
arr[right--] = temp;
}
return new String(arr);
}
}

you can try the build-in function charAt()
private String reverseString2(String str) {
if (str == null) {
return null;
}
String result = "";
for (int i = str.length() - 1; i >= 0; i--) {
result = result + str.charAt(i);
}
return result;
}
public void test(){
System.out.println(reverseString2("abcd"));
}
see also rever a string in java

String reversed = new StringBuilder(originalString).reverse().toString();

Related

Rewriting the String in Reverse [duplicate]

I have "Hello World" kept in a String variable named hi.
I need to print it, but reversed.
How can I do this? I understand there is some kind of a function already built-in into Java that does that.
Related: Reverse each individual word of “Hello World” string with Java

You can use this:
new StringBuilder(hi).reverse().toString()
StringBuilder was added in Java 5. For versions prior to Java 5, the StringBuffer class can be used instead — it has the same API.

For Online Judges problems that does not allow StringBuilder or StringBuffer, you can do it in place using char[] as following:
public static String reverse(String input){
char[] in = input.toCharArray();
int begin=0;
int end=in.length-1;
char temp;
while(end>begin){
temp = in[begin];
in[begin]=in[end];
in[end] = temp;
end--;
begin++;
}
return new String(in);
}

public static String reverseIt(String source) {
int i, len = source.length();
StringBuilder dest = new StringBuilder(len);
for (i = (len - 1); i >= 0; i--){
dest.append(source.charAt(i));
}
return dest.toString();
}
http://www.java2s.com/Code/Java/Language-Basics/ReverseStringTest.htm

String string="whatever";
String reverse = new StringBuffer(string).reverse().toString();
System.out.println(reverse);

I am doing this by using the following two ways:
Reverse string by CHARACTERS:
public static void main(String[] args) {
// Using traditional approach
String result="";
for(int i=string.length()-1; i>=0; i--) {
result = result + string.charAt(i);
}
System.out.println(result);
// Using StringBuffer class
StringBuffer buffer = new StringBuffer(string);
System.out.println(buffer.reverse());
}
Reverse string by WORDS:
public static void reverseStringByWords(String string) {
StringBuilder stringBuilder = new StringBuilder();
String[] words = string.split(" ");
for (int j = words.length-1; j >= 0; j--) {
stringBuilder.append(words[j]).append(' ');
}
System.out.println("Reverse words: " + stringBuilder);
}

Take a look at the Java 6 API under StringBuffer
String s = "sample";
String result = new StringBuffer(s).reverse().toString();

Here is an example using recursion:
public void reverseString() {
String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String reverseAlphabet = reverse(alphabet, alphabet.length()-1);
}
String reverse(String stringToReverse, int index){
if(index == 0){
return stringToReverse.charAt(0) + "";
}
char letter = stringToReverse.charAt(index);
return letter + reverse(stringToReverse, index-1);
}

Here is a low level solution:
import java.util.Scanner;
public class class1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String inpStr = in.nextLine();
System.out.println("Original String :" + inpStr);
char temp;
char[] arr = inpStr.toCharArray();
int len = arr.length;
for(int i=0; i<(inpStr.length())/2; i++,len--){
temp = arr[i];
arr[i] = arr[len-1];
arr[len-1] = temp;
}
System.out.println("Reverse String :" + String.valueOf(arr));
}
}

I tried, just for fun, by using a Stack. Here my code:
public String reverseString(String s) {
Stack<Character> stack = new Stack<>();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
stack.push(s.charAt(i));
}
while (!stack.empty()) {
sb.append(stack.pop());
}
return sb.toString();
}

Since the below method (using XOR) to reverse a string is not listed, I am attaching this method to reverse a string.
The Algorithm is based on :
1.(A XOR B) XOR B = A
2.(A XOR B) XOR A = B
Code snippet:
public class ReverseUsingXOR {
public static void main(String[] args) {
String str = "prateek";
reverseUsingXOR(str.toCharArray());
}
/*Example:
* str= prateek;
* str[low]=p;
* str[high]=k;
* str[low]=p^k;
* str[high]=(p^k)^k =p;
* str[low]=(p^k)^p=k;
*
* */
public static void reverseUsingXOR(char[] str) {
int low = 0;
int high = str.length - 1;
while (low < high) {
str[low] = (char) (str[low] ^ str[high]);
str[high] = (char) (str[low] ^ str[high]);
str[low] = (char) (str[low] ^ str[high]);
low++;
high--;
}
//display reversed string
for (int i = 0; i < str.length; i++) {
System.out.print(str[i]);
}
}
}
Output:
keetarp

As others have pointed out the preferred way is to use:
new StringBuilder(hi).reverse().toString()
But if you want to implement this by yourself, I'm afraid that the rest of responses have flaws.
The reason is that String represents a list of Unicode points, encoded in a char[] array according to the variable-length encoding: UTF-16.
This means some code points use a single element of the array (one code unit) but others use two of them, so there might be pairs of characters that must be treated as a single unit (consecutive "high" and "low" surrogates).
public static String reverseString(String s) {
char[] chars = new char[s.length()];
boolean twoCharCodepoint = false;
for (int i = 0; i < s.length(); i++) {
chars[s.length() - 1 - i] = s.charAt(i);
if (twoCharCodepoint) {
swap(chars, s.length() - 1 - i, s.length() - i);
}
twoCharCodepoint = !Character.isBmpCodePoint(s.codePointAt(i));
}
return new String(chars);
}
private static void swap(char[] array, int i, int j) {
char temp = array[i];
array[i] = array[j];
array[j] = temp;
}
public static void main(String[] args) throws Exception {
FileOutputStream fos = new FileOutputStream("C:/temp/reverse-string.txt");
StringBuilder sb = new StringBuilder("Linear B Syllable B008 A: ");
sb.appendCodePoint(65536); //http://unicode-table.com/es/#10000
sb.append(".");
fos.write(sb.toString().getBytes("UTF-16"));
fos.write("\n".getBytes("UTF-16"));
fos.write(reverseString(sb.toString()).getBytes("UTF-16"));
}

Using charAt() method
String name = "gaurav";
String reversedString = "";
for(int i = name.length()-1; i>=0; i--){
reversedString = reversedString + name.charAt(i);
}
System.out.println(reversedString);
Using toCharArray() method
String name = "gaurav";
char [] stringCharArray = name.toCharArray();
String reversedString = "";
for(int i = stringCharArray.length-1; i>=0; i--) {
reversedString = reversedString + stringCharArray[i];
}
System.out.println(reversedString);
Using reverse() method of the Stringbuilder
String name = "gaurav";
String reversedString = new StringBuilder(name).reverse().toString();
System.out.println(reversedString);
Check https://coderolls.com/reverse-a-string-in-java/

It is very simple in minimum code of lines
public class ReverseString {
public static void main(String[] args) {
String s1 = "neelendra";
for(int i=s1.length()-1;i>=0;i--)
{
System.out.print(s1.charAt(i));
}
}
}

This did the trick for me
public static void main(String[] args) {
String text = "abcdefghijklmnopqrstuvwxyz";
for (int i = (text.length() - 1); i >= 0; i--) {
System.out.print(text.charAt(i));
}
}

1. Using Character Array:
public String reverseString(String inputString) {
char[] inputStringArray = inputString.toCharArray();
String reverseString = "";
for (int i = inputStringArray.length - 1; i >= 0; i--) {
reverseString += inputStringArray[i];
}
return reverseString;
}
2. Using StringBuilder:
public String reverseString(String inputString) {
StringBuilder stringBuilder = new StringBuilder(inputString);
stringBuilder = stringBuilder.reverse();
return stringBuilder.toString();
}
OR
return new StringBuilder(inputString).reverse().toString();

System.out.print("Please enter your name: ");
String name = keyboard.nextLine();
String reverse = new StringBuffer(name).reverse().toString();
String rev = reverse.toLowerCase();
System.out.println(rev);
I used this method to turn names backwards and into lower case.

One natural way to reverse a String is to use a StringTokenizer and a stack. Stack is a class that implements an easy-to-use last-in, first-out (LIFO) stack of objects.
String s = "Hello My name is Sufiyan";
Put it in the stack frontwards
Stack<String> myStack = new Stack<>();
StringTokenizer st = new StringTokenizer(s);
while (st.hasMoreTokens()) {
myStack.push(st.nextToken());
}
Print the stack backwards
System.out.print('"' + s + '"' + " backwards by word is:\n\t\"");
while (!myStack.empty()) {
System.out.print(myStack.pop());
System.out.print(' ');
}
System.out.println('"');

public String reverse(String s) {
String reversedString = "";
for(int i=s.length(); i>0; i--) {
reversedString += s.charAt(i-1);
}
return reversedString;
}

public class Test {
public static void main(String args[]) {
StringBuffer buffer = new StringBuffer("Game Plan");
buffer.reverse();
System.out.println(buffer);
}
}

All above solution is too good but here I am making reverse string using recursive programming.
This is helpful for who is looking recursive way of doing reverse string.
public class ReversString {
public static void main(String args[]) {
char s[] = "Dhiral Pandya".toCharArray();
String r = new String(reverse(0, s));
System.out.println(r);
}
public static char[] reverse(int i, char source[]) {
if (source.length / 2 == i) {
return source;
}
char t = source[i];
source[i] = source[source.length - 1 - i];
source[source.length - 1 - i] = t;
i++;
return reverse(i, source);
}
}

You can also try this:
public class StringReverse {
public static void main(String[] args) {
String str = "Dogs hates cats";
StringBuffer sb = new StringBuffer(str);
System.out.println(sb.reverse());
}
}

Procedure :
We can use split() to split the string .Then use reverse loop and add the characters.
Code snippet:
class test
{
public static void main(String args[])
{
String str = "world";
String[] split= str.split("");
String revers = "";
for (int i = split.length-1; i>=0; i--)
{
revers += split[i];
}
System.out.printf("%s", revers);
}
}
//output : dlrow

It gets the value you typed and returns it reversed ;)
public static String reverse (String a){
char[] rarray = a.toCharArray();
String finalvalue = "";
for (int i = 0; i < rarray.length; i++)
{
finalvalue += rarray[rarray.length - 1 - i];
}
return finalvalue;
}

public String reverseWords(String s) {
String reversedWords = "";
if(s.length()<=0) {
return reversedWords;
}else if(s.length() == 1){
if(s == " "){
return "";
}
return s;
}
char arr[] = s.toCharArray();
int j = arr.length-1;
while(j >= 0 ){
if( arr[j] == ' '){
reversedWords+=arr[j];
}else{
String temp="";
while(j>=0 && arr[j] != ' '){
temp+=arr[j];
j--;
}
j++;
temp = reverseWord(temp);
reversedWords+=temp;
}
j--;
}
String[] chk = reversedWords.split(" ");
if(chk == null || chk.length == 0){
return "";
}
return reversedWords;
}
public String reverseWord(String s){
char[] arr = s.toCharArray();
for(int i=0,j=arr.length-1;i<=j;i++,j--){
char tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
return String.valueOf(arr);
}

public static void main(String[] args) {
String str = "Prashant";
int len = str.length();
char[] c = new char[len];
for (int j = len - 1, i = 0; j >= 0; j--, i++) {
c[i] = str.charAt(j);
}
str = String.copyValueOf(c);
System.out.println(str);
}

public void reverString(){
System.out.println("Enter value");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
try{
String str=br.readLine();
char[] charArray=str.toCharArray();
for(int i=charArray.length-1; i>=0; i--){
System.out.println(charArray[i]);
}
}
catch(IOException ex){
}

recursion:
public String stringReverse(String string) {
if (string == null || string.length() == 0) {
return string;
}
return stringReverse(string.substring(1)) + string.charAt(0);
}

Sequence of characters (or) StringString's Family:
String testString = "Yashwanth#777"; // ~1 1⁄4→D800₁₆«2²⁰
Using Java 8 Stream API
First we convert String into stream by using method CharSequence.chars(), then we use the method IntStream.range to generate a sequential stream of numbers. Then we map this sequence of stream into String.
public static String reverseString_Stream(String str) {
IntStream cahrStream = str.chars();
final int[] array = cahrStream.map( x -> x ).toArray();
int from = 0, upTo = array.length;
IntFunction<String> reverseMapper = (i) -> ( Character.toString((char) array[ (upTo - i) + (from - 1) ]) );
String reverseString = IntStream.range(from, upTo) // for (int i = from; i < upTo ; i++) { ... }
.mapToObj( reverseMapper ) // array[ lastElement ]
.collect(Collectors.joining()) // Joining stream of elements together into a String.
.toString(); // This object (which is already a string!) is itself returned.
System.out.println("Reverse Stream as String : "+ reverseString);
return reverseString;
}
Using a Traditional for Loop
If you want to reverse the string then we need to follow these steps.
Convert String into an Array of Characters.
Iterate over an array in reverse order, append each Character to temporary string variable until the last character.
public static String reverseString( String reverse ) {
if( reverse != null && reverse != "" && reverse.length() > 0 ) {
char[] arr = reverse.toCharArray();
String temp = "";
for( int i = arr.length-1; i >= 0; i-- ) {
temp += arr[i];
}
System.out.println("Reverse String : "+ temp);
}
return null;
}
Easy way to Use reverse method provided form StringBuffer or StringBuilder Classes
StringBuilder and StringBuffer are mutable sequence of characters. That means one can change the value of these object's.
StringBuffer buffer = new StringBuffer(str);
System.out.println("StringBuffer - reverse : "+ buffer.reverse() );
String builderString = (new StringBuilder(str)).reverse().toString;
System.out.println("StringBuilder generated reverse String : "+ builderString );
StringBuffer has the same methods as the StringBuilder, but each method in StringBuffer is synchronized so it is thread safe.

public static String revString(String str){
char[] revCharArr = str.toCharArray();
for (int i=0; i< str.length()/2; i++){
char f = revCharArr[i];
char l = revCharArr[str.length()-i-1];
revCharArr[i] = l;
revCharArr[str.length()-i-1] = f;
}
String revStr = new String(revCharArr);
return revStr;
}

Simple For loop in java
public void reverseString(char[] s) {
int length = s.length;
for (int i = 0; i < s.length / 2; i++) {
// swaping character
char temp = s[length - i - 1];
s[length - i - 1] = s[i];
s[i] = temp;
}
}

How can I move multiple character arrays to the back of an array based upon a specific index?

I have a string "Hello, World!" that I have to convert into a char array. I then found the index of the char ',' - to which I want to create a new char array that contains " World!, Hello".
I've got the first index of the char array moved to the back - such that it prints out "ello, World!H".
How can I use my variable indexDelimiter to move the rest of the char arrays (as well as the ',') to the back? I've been looking at this problem forever, and I'm very confused as to how I could go about this.
I can't use ListArray. I has to be an Array.
public class ArrayTest {
public static void main(String[] args) {
String s = "Hello, World!";
char[] oldCharArray = s.toCharArray();
char[] newCharArray = new char[oldCharArray.length];
char delimiter = ',';
int indexDelimiter = new String(oldCharArray).indexOf(delimiter);
for (int i = 0; i < oldCharArray.length - 1; i++) {
newCharArray[i] = oldCharArray[i + 1];
}
newCharArray[oldCharArray.length - 1] = oldCharArray[0];
for (int i = 0; i < newCharArray.length; i++) {
System.out.print(newCharArray[i]);
}
// This prints out "ello, World!H" but I want " World!, Hello"
}
}

This code will produce "World!,Hello", take a look and see if it meets your needs.
public static void main(String args[]) {
String s = "Hello, World!";
char[] oldCharArray = s.toCharArray();
char[] newCharArray = new char[oldCharArray.length];
char delimiter = ',';
int indexDelimiter = new String(oldCharArray).indexOf(delimiter);
int i = 0;
for (i = 0; i < oldCharArray.length-indexDelimiter-1; i++) {
newCharArray[i] = oldCharArray[indexDelimiter + i + 1];
}
newCharArray[i] = delimiter;
i++;
int j = i;
while (i < oldCharArray.length) {
newCharArray[i] = oldCharArray[i - j];
i++;
}
System.out.println(newCharArray);
}

If you mean backward, you can reverse the by splitting it first
public char[] reverse_comma_split(String str) {
String[] spl = str.split(",");
String reversed = new String();
for (int i = spl.length - 1; i >= 0; i--) {
reversed += spl[i];
if (i != 0)
reversed += ", ";
}
return reversed.toCharArray();
}
Calling reverse_comma_split("Hello, world!") would return a char array of " world!, Hello"
However, if you insist to get uppercase char in every split, you can modify the loop in which spl[i] to spl[i].substring(0, 1).toUpperCase() + spl[i].substring(1)

Is reversing a string this way bad practice? [Java] [duplicate]

I have "Hello World" kept in a String variable named hi.
I need to print it, but reversed.
How can I do this? I understand there is some kind of a function already built-in into Java that does that.
Related: Reverse each individual word of “Hello World” string with Java

You can use this:
new StringBuilder(hi).reverse().toString()
StringBuilder was added in Java 5. For versions prior to Java 5, the StringBuffer class can be used instead — it has the same API.

For Online Judges problems that does not allow StringBuilder or StringBuffer, you can do it in place using char[] as following:
public static String reverse(String input){
char[] in = input.toCharArray();
int begin=0;
int end=in.length-1;
char temp;
while(end>begin){
temp = in[begin];
in[begin]=in[end];
in[end] = temp;
end--;
begin++;
}
return new String(in);
}

public static String reverseIt(String source) {
int i, len = source.length();
StringBuilder dest = new StringBuilder(len);
for (i = (len - 1); i >= 0; i--){
dest.append(source.charAt(i));
}
return dest.toString();
}
http://www.java2s.com/Code/Java/Language-Basics/ReverseStringTest.htm

String string="whatever";
String reverse = new StringBuffer(string).reverse().toString();
System.out.println(reverse);

I am doing this by using the following two ways:
Reverse string by CHARACTERS:
public static void main(String[] args) {
// Using traditional approach
String result="";
for(int i=string.length()-1; i>=0; i--) {
result = result + string.charAt(i);
}
System.out.println(result);
// Using StringBuffer class
StringBuffer buffer = new StringBuffer(string);
System.out.println(buffer.reverse());
}
Reverse string by WORDS:
public static void reverseStringByWords(String string) {
StringBuilder stringBuilder = new StringBuilder();
String[] words = string.split(" ");
for (int j = words.length-1; j >= 0; j--) {
stringBuilder.append(words[j]).append(' ');
}
System.out.println("Reverse words: " + stringBuilder);
}

Take a look at the Java 6 API under StringBuffer
String s = "sample";
String result = new StringBuffer(s).reverse().toString();

Here is an example using recursion:
public void reverseString() {
String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String reverseAlphabet = reverse(alphabet, alphabet.length()-1);
}
String reverse(String stringToReverse, int index){
if(index == 0){
return stringToReverse.charAt(0) + "";
}
char letter = stringToReverse.charAt(index);
return letter + reverse(stringToReverse, index-1);
}

Here is a low level solution:
import java.util.Scanner;
public class class1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String inpStr = in.nextLine();
System.out.println("Original String :" + inpStr);
char temp;
char[] arr = inpStr.toCharArray();
int len = arr.length;
for(int i=0; i<(inpStr.length())/2; i++,len--){
temp = arr[i];
arr[i] = arr[len-1];
arr[len-1] = temp;
}
System.out.println("Reverse String :" + String.valueOf(arr));
}
}

I tried, just for fun, by using a Stack. Here my code:
public String reverseString(String s) {
Stack<Character> stack = new Stack<>();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
stack.push(s.charAt(i));
}
while (!stack.empty()) {
sb.append(stack.pop());
}
return sb.toString();
}

Since the below method (using XOR) to reverse a string is not listed, I am attaching this method to reverse a string.
The Algorithm is based on :
1.(A XOR B) XOR B = A
2.(A XOR B) XOR A = B
Code snippet:
public class ReverseUsingXOR {
public static void main(String[] args) {
String str = "prateek";
reverseUsingXOR(str.toCharArray());
}
/*Example:
* str= prateek;
* str[low]=p;
* str[high]=k;
* str[low]=p^k;
* str[high]=(p^k)^k =p;
* str[low]=(p^k)^p=k;
*
* */
public static void reverseUsingXOR(char[] str) {
int low = 0;
int high = str.length - 1;
while (low < high) {
str[low] = (char) (str[low] ^ str[high]);
str[high] = (char) (str[low] ^ str[high]);
str[low] = (char) (str[low] ^ str[high]);
low++;
high--;
}
//display reversed string
for (int i = 0; i < str.length; i++) {
System.out.print(str[i]);
}
}
}
Output:
keetarp

As others have pointed out the preferred way is to use:
new StringBuilder(hi).reverse().toString()
But if you want to implement this by yourself, I'm afraid that the rest of responses have flaws.
The reason is that String represents a list of Unicode points, encoded in a char[] array according to the variable-length encoding: UTF-16.
This means some code points use a single element of the array (one code unit) but others use two of them, so there might be pairs of characters that must be treated as a single unit (consecutive "high" and "low" surrogates).
public static String reverseString(String s) {
char[] chars = new char[s.length()];
boolean twoCharCodepoint = false;
for (int i = 0; i < s.length(); i++) {
chars[s.length() - 1 - i] = s.charAt(i);
if (twoCharCodepoint) {
swap(chars, s.length() - 1 - i, s.length() - i);
}
twoCharCodepoint = !Character.isBmpCodePoint(s.codePointAt(i));
}
return new String(chars);
}
private static void swap(char[] array, int i, int j) {
char temp = array[i];
array[i] = array[j];
array[j] = temp;
}
public static void main(String[] args) throws Exception {
FileOutputStream fos = new FileOutputStream("C:/temp/reverse-string.txt");
StringBuilder sb = new StringBuilder("Linear B Syllable B008 A: ");
sb.appendCodePoint(65536); //http://unicode-table.com/es/#10000
sb.append(".");
fos.write(sb.toString().getBytes("UTF-16"));
fos.write("\n".getBytes("UTF-16"));
fos.write(reverseString(sb.toString()).getBytes("UTF-16"));
}

Using charAt() method
String name = "gaurav";
String reversedString = "";
for(int i = name.length()-1; i>=0; i--){
reversedString = reversedString + name.charAt(i);
}
System.out.println(reversedString);
Using toCharArray() method
String name = "gaurav";
char [] stringCharArray = name.toCharArray();
String reversedString = "";
for(int i = stringCharArray.length-1; i>=0; i--) {
reversedString = reversedString + stringCharArray[i];
}
System.out.println(reversedString);
Using reverse() method of the Stringbuilder
String name = "gaurav";
String reversedString = new StringBuilder(name).reverse().toString();
System.out.println(reversedString);
Check https://coderolls.com/reverse-a-string-in-java/

It is very simple in minimum code of lines
public class ReverseString {
public static void main(String[] args) {
String s1 = "neelendra";
for(int i=s1.length()-1;i>=0;i--)
{
System.out.print(s1.charAt(i));
}
}
}

This did the trick for me
public static void main(String[] args) {
String text = "abcdefghijklmnopqrstuvwxyz";
for (int i = (text.length() - 1); i >= 0; i--) {
System.out.print(text.charAt(i));
}
}

1. Using Character Array:
public String reverseString(String inputString) {
char[] inputStringArray = inputString.toCharArray();
String reverseString = "";
for (int i = inputStringArray.length - 1; i >= 0; i--) {
reverseString += inputStringArray[i];
}
return reverseString;
}
2. Using StringBuilder:
public String reverseString(String inputString) {
StringBuilder stringBuilder = new StringBuilder(inputString);
stringBuilder = stringBuilder.reverse();
return stringBuilder.toString();
}
OR
return new StringBuilder(inputString).reverse().toString();

System.out.print("Please enter your name: ");
String name = keyboard.nextLine();
String reverse = new StringBuffer(name).reverse().toString();
String rev = reverse.toLowerCase();
System.out.println(rev);
I used this method to turn names backwards and into lower case.

One natural way to reverse a String is to use a StringTokenizer and a stack. Stack is a class that implements an easy-to-use last-in, first-out (LIFO) stack of objects.
String s = "Hello My name is Sufiyan";
Put it in the stack frontwards
Stack<String> myStack = new Stack<>();
StringTokenizer st = new StringTokenizer(s);
while (st.hasMoreTokens()) {
myStack.push(st.nextToken());
}
Print the stack backwards
System.out.print('"' + s + '"' + " backwards by word is:\n\t\"");
while (!myStack.empty()) {
System.out.print(myStack.pop());
System.out.print(' ');
}
System.out.println('"');

public String reverse(String s) {
String reversedString = "";
for(int i=s.length(); i>0; i--) {
reversedString += s.charAt(i-1);
}
return reversedString;
}

public class Test {
public static void main(String args[]) {
StringBuffer buffer = new StringBuffer("Game Plan");
buffer.reverse();
System.out.println(buffer);
}
}

All above solution is too good but here I am making reverse string using recursive programming.
This is helpful for who is looking recursive way of doing reverse string.
public class ReversString {
public static void main(String args[]) {
char s[] = "Dhiral Pandya".toCharArray();
String r = new String(reverse(0, s));
System.out.println(r);
}
public static char[] reverse(int i, char source[]) {
if (source.length / 2 == i) {
return source;
}
char t = source[i];
source[i] = source[source.length - 1 - i];
source[source.length - 1 - i] = t;
i++;
return reverse(i, source);
}
}

You can also try this:
public class StringReverse {
public static void main(String[] args) {
String str = "Dogs hates cats";
StringBuffer sb = new StringBuffer(str);
System.out.println(sb.reverse());
}
}

Procedure :
We can use split() to split the string .Then use reverse loop and add the characters.
Code snippet:
class test
{
public static void main(String args[])
{
String str = "world";
String[] split= str.split("");
String revers = "";
for (int i = split.length-1; i>=0; i--)
{
revers += split[i];
}
System.out.printf("%s", revers);
}
}
//output : dlrow

It gets the value you typed and returns it reversed ;)
public static String reverse (String a){
char[] rarray = a.toCharArray();
String finalvalue = "";
for (int i = 0; i < rarray.length; i++)
{
finalvalue += rarray[rarray.length - 1 - i];
}
return finalvalue;
}

public String reverseWords(String s) {
String reversedWords = "";
if(s.length()<=0) {
return reversedWords;
}else if(s.length() == 1){
if(s == " "){
return "";
}
return s;
}
char arr[] = s.toCharArray();
int j = arr.length-1;
while(j >= 0 ){
if( arr[j] == ' '){
reversedWords+=arr[j];
}else{
String temp="";
while(j>=0 && arr[j] != ' '){
temp+=arr[j];
j--;
}
j++;
temp = reverseWord(temp);
reversedWords+=temp;
}
j--;
}
String[] chk = reversedWords.split(" ");
if(chk == null || chk.length == 0){
return "";
}
return reversedWords;
}
public String reverseWord(String s){
char[] arr = s.toCharArray();
for(int i=0,j=arr.length-1;i<=j;i++,j--){
char tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
return String.valueOf(arr);
}

public static void main(String[] args) {
String str = "Prashant";
int len = str.length();
char[] c = new char[len];
for (int j = len - 1, i = 0; j >= 0; j--, i++) {
c[i] = str.charAt(j);
}
str = String.copyValueOf(c);
System.out.println(str);
}

public void reverString(){
System.out.println("Enter value");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
try{
String str=br.readLine();
char[] charArray=str.toCharArray();
for(int i=charArray.length-1; i>=0; i--){
System.out.println(charArray[i]);
}
}
catch(IOException ex){
}

recursion:
public String stringReverse(String string) {
if (string == null || string.length() == 0) {
return string;
}
return stringReverse(string.substring(1)) + string.charAt(0);
}

Sequence of characters (or) StringString's Family:
String testString = "Yashwanth#777"; // ~1 1⁄4→D800₁₆«2²⁰
Using Java 8 Stream API
First we convert String into stream by using method CharSequence.chars(), then we use the method IntStream.range to generate a sequential stream of numbers. Then we map this sequence of stream into String.
public static String reverseString_Stream(String str) {
IntStream cahrStream = str.chars();
final int[] array = cahrStream.map( x -> x ).toArray();
int from = 0, upTo = array.length;
IntFunction<String> reverseMapper = (i) -> ( Character.toString((char) array[ (upTo - i) + (from - 1) ]) );
String reverseString = IntStream.range(from, upTo) // for (int i = from; i < upTo ; i++) { ... }
.mapToObj( reverseMapper ) // array[ lastElement ]
.collect(Collectors.joining()) // Joining stream of elements together into a String.
.toString(); // This object (which is already a string!) is itself returned.
System.out.println("Reverse Stream as String : "+ reverseString);
return reverseString;
}
Using a Traditional for Loop
If you want to reverse the string then we need to follow these steps.
Convert String into an Array of Characters.
Iterate over an array in reverse order, append each Character to temporary string variable until the last character.
public static String reverseString( String reverse ) {
if( reverse != null && reverse != "" && reverse.length() > 0 ) {
char[] arr = reverse.toCharArray();
String temp = "";
for( int i = arr.length-1; i >= 0; i-- ) {
temp += arr[i];
}
System.out.println("Reverse String : "+ temp);
}
return null;
}
Easy way to Use reverse method provided form StringBuffer or StringBuilder Classes
StringBuilder and StringBuffer are mutable sequence of characters. That means one can change the value of these object's.
StringBuffer buffer = new StringBuffer(str);
System.out.println("StringBuffer - reverse : "+ buffer.reverse() );
String builderString = (new StringBuilder(str)).reverse().toString;
System.out.println("StringBuilder generated reverse String : "+ builderString );
StringBuffer has the same methods as the StringBuilder, but each method in StringBuffer is synchronized so it is thread safe.

public static String revString(String str){
char[] revCharArr = str.toCharArray();
for (int i=0; i< str.length()/2; i++){
char f = revCharArr[i];
char l = revCharArr[str.length()-i-1];
revCharArr[i] = l;
revCharArr[str.length()-i-1] = f;
}
String revStr = new String(revCharArr);
return revStr;
}

Simple For loop in java
public void reverseString(char[] s) {
int length = s.length;
for (int i = 0; i < s.length / 2; i++) {
// swaping character
char temp = s[length - i - 1];
s[length - i - 1] = s[i];
s[i] = temp;
}
}

Java words reverse

I am new to Java and I found a interesting problem which I wanted to solve. I am trying to code a program that reverses the position of each word of a string. For example, the input string = "HERE AM I", the output string will be "I AM HERE". I have got into it, but it's not working out for me. Could anyone kindly point out the error, and how to fix it, because I am really curious to know what's going wrong. Thanks!
import java.util.Scanner;
public class Count{
static Scanner sc = new Scanner(System.in);
static String in = ""; static String ar[];
void accept(){
System.out.println("Enter the string: ");
in = sc.nextLine();
}
void intArray(int words){
ar = new String[words];
}
static int Words(String in){
in = in.trim(); //Rm space
int wc = 1;
char c;
for (int i = 0; i<in.length()-1;i++){
if (in.charAt(i)==' '&&in.charAt(i+1)!=' ') wc++;
}
return wc;
}
void generate(){
char c; String w = ""; int n = 0;
for (int i = 0; i<in.length(); i++){
c = in.charAt(i);
if (c!=' '){
w += c;
}
else {
ar[n] = w; n++;
}
}
}
void printOut(){
String finale = "";
for (int i = ar.length-1; i>=0;i--){
finale = finale + (ar[i]);
}
System.out.println("Reversed words: " + finale);
}
public static void main(String[] args){
Count a = new Count();
a.accept();
int words = Words(in);
a.intArray(words);
a.generate();
a.printOut();
}
}

Got it. Here is my code that implements split and reverse from scratch.
The split function is implemented through iterating through the string, and keeping track of start and end indexes. Once one of the indexes in the string is equivalent to a " ", the program sets the end index to the element behind the space, and adds the previous substring to an ArrayList, then creating a new start index to begin with.
Reverse is very straightforward - you simply iterate from the end of the string to the first element of the string.
Example:
Input: df gf sd
Output: sd gf df
import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;
public class Count{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("Enter string to reverse: ");
String unreversed = scan.nextLine();
System.out.println("Reversed String: " + reverse(unreversed));
}
public static String reverse(String unreversed)
{
ArrayList<String> parts = new ArrayList<String>();
String reversed = "";
int start = 0;
int end = 0;
for (int i = 0; i < unreversed.length(); i++)
{
if (unreversed.charAt(i) == ' ')
{
end = i;
parts.add(unreversed.substring(start, end));
start = i + 1;
}
}
parts.add(unreversed.substring(start, unreversed.length()));
for (int i = parts.size()-1; i >= 0; i--)
{
reversed += parts.get(i);
reversed += " ";
}
return reversed;
}
}

There is my suggestion :
String s = " HERE AM I ";
s = s.trim();
int j = s.length() - 1;
int index = 0;
StringBuilder builder = new StringBuilder();
for (int i = j; i >= 0; i--) {
Character c = s.charAt(i);
if (c.isWhitespace(c)) {
index = i;
String r = s.substring(index+1, j+1);
j = index - 1;
builder.append(r);
builder.append(" ");
}
}
String r=s.substring(0, index);
builder.append(r);
System.out.println(builder.toString());

From adding debug output between each method call it's easy to determine that you're successfully reading the input, counting the words, and initializing the array. That means that the problem is in generate().
Problem 1 in generate() (why "HERE" is duplicated in the output): after you add w to your array (when the word is complete) you don't reset w to "", meaning every word has the previous word(s) prepended to it. This is easily seen by adding debug output (or using a debugger) to print the state of ar and w each iteration of the loop.
Problem 2 in generate() (why "I" isn't in the output): there isn't a trailing space in the string, so the condition that adds a word to the array is never met for the last word before the loop terminates at the end of the string. The easy fix is to just add ar[n] = w; after the end of the loop to cover the last word.

I would use the split function and then print from the end of the list to the front.
String[] splitString = str.split(" ");
for(int i = splitString.length() - 1; i >= 0; i--){
System.out.print(splitString[i]);
if(i != 0) System.out.print(' ');
}
Oops read your comment. Disregard this if it is not what you want.

This has a function that does the same as split, but not the predefined split function
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the string : ");
String input = sc.nextLine();
// This splits the string into array of words separated with " "
String arr[] = myOwnSplit(input.trim(), ' '); // ["I", "AM", "HERE"]
// This ll contain the reverse string
String rev = "";
// Reading the array from the back
for(int i = (arr.length - 1) ; i >= 0 ; i --) {
// putting the words into the reverse string with a space to it's end
rev += (arr[i] + " ");
}
// Getting rid of the last extra space
rev.trim();
System.out.println("The reverse of the given string is : " + rev);
}
// The is my own version of the split function
public static String[] myOwnSplit(String str, char regex) {
char[] arr = str.toCharArray();
ArrayList<String> spltedArrayList = new ArrayList<String>();
String word = "";
// splitting the string based on the regex and bulding an arraylist
for(int i = 0 ; i < arr.length ; i ++) {
char c = arr[i];
if(c == regex) {
spltedArrayList.add(word);
word = "";
} else {
word += c;
}
if(i == (arr.length - 1)) {
spltedArrayList.add(word);
}
}
String[] splitedArray = new String[spltedArrayList.size()];
// Converting the arraylist to string array
for(int i = 0 ; i < spltedArrayList.size() ; i++) {
splitedArray[i] = spltedArrayList.get(i);
}
return splitedArray;
}

Reverseing a string in java [duplicate]

I have "Hello World" kept in a String variable named hi.
I need to print it, but reversed.
How can I do this? I understand there is some kind of a function already built-in into Java that does that.
Related: Reverse each individual word of “Hello World” string with Java

You can use this:
new StringBuilder(hi).reverse().toString()
StringBuilder was added in Java 5. For versions prior to Java 5, the StringBuffer class can be used instead — it has the same API.

For Online Judges problems that does not allow StringBuilder or StringBuffer, you can do it in place using char[] as following:
public static String reverse(String input){
char[] in = input.toCharArray();
int begin=0;
int end=in.length-1;
char temp;
while(end>begin){
temp = in[begin];
in[begin]=in[end];
in[end] = temp;
end--;
begin++;
}
return new String(in);
}

public static String reverseIt(String source) {
int i, len = source.length();
StringBuilder dest = new StringBuilder(len);
for (i = (len - 1); i >= 0; i--){
dest.append(source.charAt(i));
}
return dest.toString();
}
http://www.java2s.com/Code/Java/Language-Basics/ReverseStringTest.htm

String string="whatever";
String reverse = new StringBuffer(string).reverse().toString();
System.out.println(reverse);

I am doing this by using the following two ways:
Reverse string by CHARACTERS:
public static void main(String[] args) {
// Using traditional approach
String result="";
for(int i=string.length()-1; i>=0; i--) {
result = result + string.charAt(i);
}
System.out.println(result);
// Using StringBuffer class
StringBuffer buffer = new StringBuffer(string);
System.out.println(buffer.reverse());
}
Reverse string by WORDS:
public static void reverseStringByWords(String string) {
StringBuilder stringBuilder = new StringBuilder();
String[] words = string.split(" ");
for (int j = words.length-1; j >= 0; j--) {
stringBuilder.append(words[j]).append(' ');
}
System.out.println("Reverse words: " + stringBuilder);
}

Take a look at the Java 6 API under StringBuffer
String s = "sample";
String result = new StringBuffer(s).reverse().toString();

Here is an example using recursion:
public void reverseString() {
String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String reverseAlphabet = reverse(alphabet, alphabet.length()-1);
}
String reverse(String stringToReverse, int index){
if(index == 0){
return stringToReverse.charAt(0) + "";
}
char letter = stringToReverse.charAt(index);
return letter + reverse(stringToReverse, index-1);
}

Here is a low level solution:
import java.util.Scanner;
public class class1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String inpStr = in.nextLine();
System.out.println("Original String :" + inpStr);
char temp;
char[] arr = inpStr.toCharArray();
int len = arr.length;
for(int i=0; i<(inpStr.length())/2; i++,len--){
temp = arr[i];
arr[i] = arr[len-1];
arr[len-1] = temp;
}
System.out.println("Reverse String :" + String.valueOf(arr));
}
}

I tried, just for fun, by using a Stack. Here my code:
public String reverseString(String s) {
Stack<Character> stack = new Stack<>();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
stack.push(s.charAt(i));
}
while (!stack.empty()) {
sb.append(stack.pop());
}
return sb.toString();
}

Since the below method (using XOR) to reverse a string is not listed, I am attaching this method to reverse a string.
The Algorithm is based on :
1.(A XOR B) XOR B = A
2.(A XOR B) XOR A = B
Code snippet:
public class ReverseUsingXOR {
public static void main(String[] args) {
String str = "prateek";
reverseUsingXOR(str.toCharArray());
}
/*Example:
* str= prateek;
* str[low]=p;
* str[high]=k;
* str[low]=p^k;
* str[high]=(p^k)^k =p;
* str[low]=(p^k)^p=k;
*
* */
public static void reverseUsingXOR(char[] str) {
int low = 0;
int high = str.length - 1;
while (low < high) {
str[low] = (char) (str[low] ^ str[high]);
str[high] = (char) (str[low] ^ str[high]);
str[low] = (char) (str[low] ^ str[high]);
low++;
high--;
}
//display reversed string
for (int i = 0; i < str.length; i++) {
System.out.print(str[i]);
}
}
}
Output:
keetarp

As others have pointed out the preferred way is to use:
new StringBuilder(hi).reverse().toString()
But if you want to implement this by yourself, I'm afraid that the rest of responses have flaws.
The reason is that String represents a list of Unicode points, encoded in a char[] array according to the variable-length encoding: UTF-16.
This means some code points use a single element of the array (one code unit) but others use two of them, so there might be pairs of characters that must be treated as a single unit (consecutive "high" and "low" surrogates).
public static String reverseString(String s) {
char[] chars = new char[s.length()];
boolean twoCharCodepoint = false;
for (int i = 0; i < s.length(); i++) {
chars[s.length() - 1 - i] = s.charAt(i);
if (twoCharCodepoint) {
swap(chars, s.length() - 1 - i, s.length() - i);
}
twoCharCodepoint = !Character.isBmpCodePoint(s.codePointAt(i));
}
return new String(chars);
}
private static void swap(char[] array, int i, int j) {
char temp = array[i];
array[i] = array[j];
array[j] = temp;
}
public static void main(String[] args) throws Exception {
FileOutputStream fos = new FileOutputStream("C:/temp/reverse-string.txt");
StringBuilder sb = new StringBuilder("Linear B Syllable B008 A: ");
sb.appendCodePoint(65536); //http://unicode-table.com/es/#10000
sb.append(".");
fos.write(sb.toString().getBytes("UTF-16"));
fos.write("\n".getBytes("UTF-16"));
fos.write(reverseString(sb.toString()).getBytes("UTF-16"));
}

Using charAt() method
String name = "gaurav";
String reversedString = "";
for(int i = name.length()-1; i>=0; i--){
reversedString = reversedString + name.charAt(i);
}
System.out.println(reversedString);
Using toCharArray() method
String name = "gaurav";
char [] stringCharArray = name.toCharArray();
String reversedString = "";
for(int i = stringCharArray.length-1; i>=0; i--) {
reversedString = reversedString + stringCharArray[i];
}
System.out.println(reversedString);
Using reverse() method of the Stringbuilder
String name = "gaurav";
String reversedString = new StringBuilder(name).reverse().toString();
System.out.println(reversedString);
Check https://coderolls.com/reverse-a-string-in-java/

It is very simple in minimum code of lines
public class ReverseString {
public static void main(String[] args) {
String s1 = "neelendra";
for(int i=s1.length()-1;i>=0;i--)
{
System.out.print(s1.charAt(i));
}
}
}

This did the trick for me
public static void main(String[] args) {
String text = "abcdefghijklmnopqrstuvwxyz";
for (int i = (text.length() - 1); i >= 0; i--) {
System.out.print(text.charAt(i));
}
}

1. Using Character Array:
public String reverseString(String inputString) {
char[] inputStringArray = inputString.toCharArray();
String reverseString = "";
for (int i = inputStringArray.length - 1; i >= 0; i--) {
reverseString += inputStringArray[i];
}
return reverseString;
}
2. Using StringBuilder:
public String reverseString(String inputString) {
StringBuilder stringBuilder = new StringBuilder(inputString);
stringBuilder = stringBuilder.reverse();
return stringBuilder.toString();
}
OR
return new StringBuilder(inputString).reverse().toString();

System.out.print("Please enter your name: ");
String name = keyboard.nextLine();
String reverse = new StringBuffer(name).reverse().toString();
String rev = reverse.toLowerCase();
System.out.println(rev);
I used this method to turn names backwards and into lower case.

One natural way to reverse a String is to use a StringTokenizer and a stack. Stack is a class that implements an easy-to-use last-in, first-out (LIFO) stack of objects.
String s = "Hello My name is Sufiyan";
Put it in the stack frontwards
Stack<String> myStack = new Stack<>();
StringTokenizer st = new StringTokenizer(s);
while (st.hasMoreTokens()) {
myStack.push(st.nextToken());
}
Print the stack backwards
System.out.print('"' + s + '"' + " backwards by word is:\n\t\"");
while (!myStack.empty()) {
System.out.print(myStack.pop());
System.out.print(' ');
}
System.out.println('"');

public String reverse(String s) {
String reversedString = "";
for(int i=s.length(); i>0; i--) {
reversedString += s.charAt(i-1);
}
return reversedString;
}

public class Test {
public static void main(String args[]) {
StringBuffer buffer = new StringBuffer("Game Plan");
buffer.reverse();
System.out.println(buffer);
}
}

All above solution is too good but here I am making reverse string using recursive programming.
This is helpful for who is looking recursive way of doing reverse string.
public class ReversString {
public static void main(String args[]) {
char s[] = "Dhiral Pandya".toCharArray();
String r = new String(reverse(0, s));
System.out.println(r);
}
public static char[] reverse(int i, char source[]) {
if (source.length / 2 == i) {
return source;
}
char t = source[i];
source[i] = source[source.length - 1 - i];
source[source.length - 1 - i] = t;
i++;
return reverse(i, source);
}
}

You can also try this:
public class StringReverse {
public static void main(String[] args) {
String str = "Dogs hates cats";
StringBuffer sb = new StringBuffer(str);
System.out.println(sb.reverse());
}
}

Procedure :
We can use split() to split the string .Then use reverse loop and add the characters.
Code snippet:
class test
{
public static void main(String args[])
{
String str = "world";
String[] split= str.split("");
String revers = "";
for (int i = split.length-1; i>=0; i--)
{
revers += split[i];
}
System.out.printf("%s", revers);
}
}
//output : dlrow

It gets the value you typed and returns it reversed ;)
public static String reverse (String a){
char[] rarray = a.toCharArray();
String finalvalue = "";
for (int i = 0; i < rarray.length; i++)
{
finalvalue += rarray[rarray.length - 1 - i];
}
return finalvalue;
}

public String reverseWords(String s) {
String reversedWords = "";
if(s.length()<=0) {
return reversedWords;
}else if(s.length() == 1){
if(s == " "){
return "";
}
return s;
}
char arr[] = s.toCharArray();
int j = arr.length-1;
while(j >= 0 ){
if( arr[j] == ' '){
reversedWords+=arr[j];
}else{
String temp="";
while(j>=0 && arr[j] != ' '){
temp+=arr[j];
j--;
}
j++;
temp = reverseWord(temp);
reversedWords+=temp;
}
j--;
}
String[] chk = reversedWords.split(" ");
if(chk == null || chk.length == 0){
return "";
}
return reversedWords;
}
public String reverseWord(String s){
char[] arr = s.toCharArray();
for(int i=0,j=arr.length-1;i<=j;i++,j--){
char tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
return String.valueOf(arr);
}

public static void main(String[] args) {
String str = "Prashant";
int len = str.length();
char[] c = new char[len];
for (int j = len - 1, i = 0; j >= 0; j--, i++) {
c[i] = str.charAt(j);
}
str = String.copyValueOf(c);
System.out.println(str);
}

public void reverString(){
System.out.println("Enter value");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
try{
String str=br.readLine();
char[] charArray=str.toCharArray();
for(int i=charArray.length-1; i>=0; i--){
System.out.println(charArray[i]);
}
}
catch(IOException ex){
}

recursion:
public String stringReverse(String string) {
if (string == null || string.length() == 0) {
return string;
}
return stringReverse(string.substring(1)) + string.charAt(0);
}

Sequence of characters (or) StringString's Family:
String testString = "Yashwanth#777"; // ~1 1⁄4→D800₁₆«2²⁰
Using Java 8 Stream API
First we convert String into stream by using method CharSequence.chars(), then we use the method IntStream.range to generate a sequential stream of numbers. Then we map this sequence of stream into String.
public static String reverseString_Stream(String str) {
IntStream cahrStream = str.chars();
final int[] array = cahrStream.map( x -> x ).toArray();
int from = 0, upTo = array.length;
IntFunction<String> reverseMapper = (i) -> ( Character.toString((char) array[ (upTo - i) + (from - 1) ]) );
String reverseString = IntStream.range(from, upTo) // for (int i = from; i < upTo ; i++) { ... }
.mapToObj( reverseMapper ) // array[ lastElement ]
.collect(Collectors.joining()) // Joining stream of elements together into a String.
.toString(); // This object (which is already a string!) is itself returned.
System.out.println("Reverse Stream as String : "+ reverseString);
return reverseString;
}
Using a Traditional for Loop
If you want to reverse the string then we need to follow these steps.
Convert String into an Array of Characters.
Iterate over an array in reverse order, append each Character to temporary string variable until the last character.
public static String reverseString( String reverse ) {
if( reverse != null && reverse != "" && reverse.length() > 0 ) {
char[] arr = reverse.toCharArray();
String temp = "";
for( int i = arr.length-1; i >= 0; i-- ) {
temp += arr[i];
}
System.out.println("Reverse String : "+ temp);
}
return null;
}
Easy way to Use reverse method provided form StringBuffer or StringBuilder Classes
StringBuilder and StringBuffer are mutable sequence of characters. That means one can change the value of these object's.
StringBuffer buffer = new StringBuffer(str);
System.out.println("StringBuffer - reverse : "+ buffer.reverse() );
String builderString = (new StringBuilder(str)).reverse().toString;
System.out.println("StringBuilder generated reverse String : "+ builderString );
StringBuffer has the same methods as the StringBuilder, but each method in StringBuffer is synchronized so it is thread safe.

public static String revString(String str){
char[] revCharArr = str.toCharArray();
for (int i=0; i< str.length()/2; i++){
char f = revCharArr[i];
char l = revCharArr[str.length()-i-1];
revCharArr[i] = l;
revCharArr[str.length()-i-1] = f;
}
String revStr = new String(revCharArr);
return revStr;
}

Simple For loop in java
public void reverseString(char[] s) {
int length = s.length;
for (int i = 0; i < s.length / 2; i++) {
// swaping character
char temp = s[length - i - 1];
s[length - i - 1] = s[i];
s[i] = temp;
}
}

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Java is a programming language and computing platform first released by Sun Microsystems in 1995.

Reverse String characters in java - java

String reversed = new StringBuilder(originalString).reverse().toString();

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