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How do I reverse a number in Java using String?

I have used the below logic, but getting an exception "java.lang.StringIndexOutOfBoundsException". Help will be appreciated. Thank you!!
import java.util.Scanner;
public class Demo{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number:- ");
String number = sc.next();
for (int i = number.length(); i >= 0; i--) {
System.out.println(number.charAt(i));
}
}
}

You only need to iterate across the string halfway, swapping the characters as the indices go towards the middle. This works for even or odd length strings.
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number:- ");
char[] chars = sc.next().toCharArray();
int len = chars.length;
for (int i = 0; i < len/2; i++) {
char c1 = chars[i];
char c2 = chars[len-i-1];
chars[i] = c2;
chars[len-i-1] = c1;
}
String s = new String(chars);
System.out.println(s);
Or just use the reverse() method included in the StringBuilder class.

import java.util.Scanner;
public class Demo{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number:- ");
String number = sc.next();
for (int i = number.length() -1 ; i >= 0; i--) { // correct answer: number.lenght() -1 as array start with 0.
System.out.print(number.charAt(i)); //using print instead of println so that it display in same line
}
}
}

How to print even and odd position characters of an array of strings in Java?

Question
Given a string S of length N, that is indexed from 0 to N-1, print it's even indexed and odd indexed characters as 2 space separated strings on a single line.
Assume input starts at index position 0(which is considered even)
Input
The first line contains an integer, T (the number of test cases).
Each line i of the T subsequent lines contain a String, S.
Output
For each string S, print it's even-indexed characters, followed by space, followed by odd-indexed characters.
Sample Input
2
Hacker
Rank
Sample Output
Hce akr
Rn ak
The Code I Wrote
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
int T = scan.nextInt();
scan.nextLine();
for(int i=0 ; i<T ; i++)
{
String myString = scan.nextLine();
int evn = 0,
odd = 0,
len = myString.length();
char strE[] = new char[50],
strO[] = new char[50];
for(int j=0 ; j<len ; j++)
{
if(j%2 == 0)
{
strE[evn] = myString.charAt(j);
evn++;
}
if(j%2 == 1)
{
strO[odd] = myString.charAt(j);
odd++;
}
}
System.out.print(strE);
System.out.print(" ");
System.out.println(strO);
}
}
My Output
Hce akr
Rn ak
The Problem
As you can see, my program successfully meets the test case, and other test cases (using custom input) but every time the HackerRank compiler tells me that my program did not meet the test case.
Clearly, my program is producing the required output but every time the HackerRank compiler tells me that I got the solution wrong.
Could anyone please tell me where I am making a mistake?
Further Modifications
I then decided to change the last 3 lines of print statements into one statement as follows:
System.out.println(strE + " " + strO);
However, this time the program did not produce the desired output and rather printed some garbage values as follows:
[C#5c3f3b9b [C#3b626c6d
[C#3abc8690 [C#2f267610
My Doubts
1. In the first case, when I was printing the two strings separately using 2 print statements, I was getting a correct output everytime but the HackerRank compiler rejected it. Why?
2. In the second case, when I modified the program by using one print statement instead of 3 to get the desired result, the program gave a completely different output and rather printed garbage values! Why?
Here is a link to the HackerRank problem for more info:
hackerrank.com/challenges/30-review-loop
All help and guidance is greatly appreciated and thanks a lot in advance!

Try to submit this:
Scanner scan = new Scanner(System.in);
int T = scan.nextInt();
scan.nextLine();
for (int i = 0; i < T; i++) {
String myString = scan.nextLine();
String even = "";
String odd = "";
for (int j = 0; j < myString.length(); j++) {
if (j % 2 == 0) {
even += myString.charAt(j);
} else {
odd += myString.charAt(j);
}
}
System.out.println(even + " " + odd);
}
i get the right output and it should meet all the requirements. i think your code fails because its not a real string you print in the end and you have empty spots in your arrays

Scanner scanner = new Scanner(System.in);
System.out.println("Enter the no.of test-cases:");
int t = scanner.nextInt();
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the String(s)");
for (int i = 0; i < t; i++) {
String myString = br.readLine();
String even = "";
String odd = "";
for (int j = 0; j < myString.length(); j++) {
if (j % 2 == 0) {
even += myString.charAt(j);
} else {
odd += myString.charAt(j);
}
}
System.out.println(even);
System.out.println(odd);
}
scanner.close();

int T = scan.nextInt();
This reads quantity of test cases, which we're going to process.
String string[] = new String[T];
for(int i = 0; i<T; i++){
string[i] = scan.next();
}
Next we're creating an array named "string" (BTW, this a bad name for variables/objects) which has size T and in the for loop reading test cases from the input T times and saving them in the array.
for(int temp = 0; temp<T; temp++){
Now, for each of test cases we do the following...
for(int j = 0; j<string[temp].length(); j = j+2)
{
System.out.print(string[temp].charAt(j));
}
We create a local variable j, which is visible only in this for loop. j holds index of the string (=string[temp]), which we're processing. So, we're printing a character on position j (by using standard method "charAt" of String class, which returns character of given index of the string) and then increasing it by 2. So, this code will print every even character. For string "example", it will print "eape" (j=0, j=2, j=4, j=6).
System.out.print(" ");
Separating sequences with a space.
for(int j = 1; j<string[temp].length(); j = j+2){
System.out.print(string[temp].charAt(j));
}
System.out.println();
We're doing the same (creating index j, running though all characters of the string), but starting from "1", so it will print all odd characters of the string. For string "example", it will give you "xml" (j=1, j=3, j=5). and After this, it will end the string. I hope, it will help you to understand. :)

I can solve your the second question:
---> System.out.print(strE);-->At the bottom, the method is called( public void print(char s[]));
-->System.out.println(strE + " " + strO);-->At the bottom, the method is called (public void println(String x) )

For your first answer I am unable to answer you as I have no idea about how the compiler works, but I can answer your second question.
The reason why System.out.print(strE); System.out.print(" "); System.out.println(strO); works is because System.out.print(char[]) and System.out.println(char[]) automatically turn the char arrays into a readable string before printing it.
However, in the second case System.out.println(strE + " " + strO);, what you are doing is directly turning the char array into strings, which just prints the class and the hash code of the array object because the toString() method is not overriden in the array class. What you want to do is System.out.println(new String(strE) + " " + new String(strO));. It will give you the result you want.

import java.io.*;
import java.util.*;
public class Solution {
private static void f(String s) {
// TODO Auto-generated method stub
char c[]=s.toCharArray();
int i,j;
for (i = 0; i <c.length;i++){
System.out.print(c[i]);
i+=1;
}
System.out.print(" ");
for (j = 1; j<c.length;j++){
System.out.print(c[j]);
j+=1;
}
}
public static void main(String[] args){
// TODO Auto-generated method stub
Scanner sc=new Scanner(System.in);
int s=sc.nextInt();
while(hasNext()){
//for loop for multiple strings as per the input
for(int m=0;m<= s;m++){
String s1=sc.next();
f(s1);
System.out.println();
}
}
}
}

I've solved this question in 2 ways & both are producing correct output.
Have a look & let me know if you've any problem.
Instead of using char array, you can use String
//char[] even = new char[10000];
String even = "";
Let's look at the code
private static Scanner scanner = new Scanner(System.in);
public static void main(String[] args) {
String s = scanner.next();
char[] array = s.toCharArray();
int count=0;
//char[] even = new char[10000];
//char[] odd = new char[10000];
String even = "";
String odd = "";
for(char ch : array){
if(count%2 == 0){
even = even + ch;
}else{
odd = odd + ch;
}
count++;
}
count = 0;
System.out.println(even + " " + odd);
}
Output:
hacker
hce akr
No need of extra char[] or String to store even & odd position characters, we can directly print them using appropriate condition.
private static Scanner scanner = new Scanner(System.in);
public static void main(String[] args){
String s = scanner.next();
char[] array = s.toCharArray();
int count=0;
for(char ch : array){
if(count%2 == 0){
System.out.print(ch);
}
count++;
}
count = 0;
System.out.print(" ");
for(char ch : array){
if(count%2 != 0){
System.out.print(ch);
}
count++;
}
count = 0;
}
Output:
hacker
hce akr

Try this:
public static void main(String[] args) {
System.out.println("Enter string to check:");
Scanner scan = new Scanner(System.in);
String T = scan.nextLine();
String even = "";
String odd = "";
for (int j = 0; j < T.length(); j++) {
if (j % 2 == 0) { //check the position of the alphabet by dividing it by 0
even += T.charAt(j);
} else {
odd += T.charAt(j);
}
}
System.out.println(even + " " + odd);
scan.close();
}

** JavaScript version **
function processData(input) {
for (let i = 1; i < input.length; i++) {
printOutput(input[i]);
}
}
function printOutput(input) {
var result = [];
input.length % 2 == 0 ? result[input.length / 2] = ' ': result[Math.ceil(input.length / 2)] = ' ';
for (let i = 0; i < input.length; i++) {
if (i % 2 == 0) {
result[i / 2] = input[i];
}
else {
result[Math.ceil(input.length / 2) + Math.ceil(i / 2)] = input[i];
}
}
console.log(result.join(''));
}
process.stdin.on("end", function () {
processData(_input.split('\n'));
});

import java.io. * ;
import java.util. * ;
public class Solution {
String myString;
public Solution(String myString) {
this.myString = myString;
int len = myString.length();
for (int j = 0; j < len; j++) {
if (j % 2 == 0) {
System.out.print(myString.charAt(j));
}
}
System.out.print(" ");
for (int j = 0; j < len; j++) {
if (j % 2 == 1) {
System.out.print(myString.charAt(j));
}
}
}
public static void main(String[] args) {
/* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
Scanner sc = new Scanner(System. in );
int T = sc.nextInt();
for (int i = 0; i < T; i++) {
String word = sc.next();
Solution sol = new Solution(word);
System.out.println();
}
sc.close();
}
}

import java.io.*;
import java.util.*;
public class Solution {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int T;
T = s.nextInt();
String[] str = new String[T];
int i;
for(i=0;i<T;i++) {
str[i] = s.next();
}
for(i=0;i<T;i++) {
char[] even = new char[5000];
char[] odd = new char[5000];
int ev =0,od=0;
for(int j= 0;j< str[i].length();j++) {
if(j%2== 0) {
even[ev] = str[i].charAt(j);
ev++;
}else {
odd[od] = str[i].charAt(j);
od++;
}
}
String strEven = new String(even);
String strOdd = new String(odd);
System.out.print(strEven.trim());
System.out.print(" ");
System.out.println(strOdd.trim());
}
s.close();
}
}
I am sure that this will work You've forgotten to convert it to a string and also increase the size of the character array

import java.io.*;
import java.util.*;
public class Solution {
public static void main(String[] args) {
Scanner scan= new Scanner(System.in);
int n= scan.nextInt();
for(int i=0;i<n;i++){
String s= scan.next();
int len= s.length();
StringBuffer str_e= new StringBuffer();
StringBuffer str_o= new StringBuffer();
for(int j=0;j<len;j++){
if(j%2==0)
str_e= str_e.append(s.charAt(j));
if(j%2==1)
str_o= str_o.append(s.charAt(j));
}
System.out.println(str_e+" "+str_o);
}
}
}

Try this:
import java.io.*;
import java.util.*;
public class Solution {
public static void main(String[] args) {
/* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
Scanner pp=new Scanner(System.in);
int n=pp.nextInt();
for(int i=0; i<n; i++)
{
String ip=pp.next();
String re1="",
re2="";
for(int j=0; j<ip.length(); j++)
{
if(j%2 == 0)
{
re1+= ip.charAt(j);
}
if(j%2 == 1)
{
re2+= ip.charAt(j);
}
}
System.out.print(re1+" "+re2);
System.out.println("");
}
}
}

public class PrintCharacters{
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int noOfTestCases = sc.nextInt();
sc.nextLine();
String []inputStrings= new String[noOfTestCases];
for(int i=0;i<noOfTestCases;i++) {
inputStrings[i]=sc.nextLine();
}
for(String str: inputStrings) {
String even ="";
String odd ="";
for(int i=0;i<str.length();i++) {
if(i%2==0) {
even+=str.charAt(i);
}else {
odd+=str.charAt(i);
}
}
System.out.println(even+" "+odd);
}
sc.close();
}
}
Input:
2
Hacker
Rank
Output:
Hce akr
Rn ak

import java.util.*;
public class Solution {
public static void main(String[] args) {
/* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
while(n>0) {
String str=scan.next();
for(int i=0;i<str.length();i++) {
if(i%2==0) {
System.out.print(str.charAt(i));
}
}
System.out.print(" ");
for(int i=0;i<str.length();i++) {
if(i%2==1) {
System.out.print(str.charAt(i));
}
}
n--;
System.out.println();
}
}
}

Use a while loop to display letters entered by a user in vertical order?

I'm trying to create a script that will ask a user to input a word and then display back the letters entered by the user in vertical order. The problem is that I'm required to use a while loop, any ideas??????
import java.util.Scanner;
public class VerticalWords {
public static void main(String[] args) {
System.out.println("Enter A word");
Scanner scan = new Scanner(System.in);
String word = scan.nextLine();
for(char a : word.toCharArray())
{
System.out.println("Letter: " + a);
}
}
}
I have tried that code, and it works but its not a while loop ^

Try this:
System.out.println("Enter A word");
Scanner scan = new Scanner(System.in);
int a = 0;
String word = scan.nextLine();
while(a < word.length){
System.out.println(word.charAt(a));
a++;
}

import java.util.Scanner;
public class VerticalWords {
public static void main(String[] args){
// TODO Auto-generated method stub
System.out.println("Enter A word: ");
Scanner scan = new Scanner(System.in);
int a = 0;
String word = scan.nextLine();
while(a < word.length())
{
System.out.println("Letter: " + (word.charAt(a)));
a++;
}
}
}

Counting white-spaces in a String in java

I have written a program which takes a String as user input and displays the count of letters, digits and white-spaces. I wrote the code using the Tokenizer-class, and it counts the letters and digits, but it leaves out the white-spaces. Any ideas?
import java.util.Scanner;
public class line {
public static void main(String[] args) {
System.out.println("Enter anything you want.");
String text;
int let = 0;
int dig = 0;
int space= 0;
Scanner sc = new Scanner(System.in);
text = sc.next();
char[]arr=text.toCharArray();
for(int i=0;i<text.length();i++) {
if (Character.isDigit(arr[i])) {
dig++;
} else if (Character.isLetter(arr[i])) {
let++;
} else if (Character.isWhitespace(arr[i])) {
space++;
}
}
System.out.println("Number of Letters : "+let);
System.out.println("Number of Digits : "+dig);
System.out.println("Number of Whitespaces : "+space);
}
}

Scanner by default breaks the input into tokens, using whitespace as the delimiter!
Simply put, it gobbles up all the whitespace!
You can change the delimiter to something else using sc.useDelimiter(/*ToDo - suitable character here - a semicolon perhaps*/).

You have got problem in
sc.next();
except it, use
sc.nextLine();
it should work.

Instead of text = sc.next(); use text = sc.nextLine();

Try using
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Line {
public static void main(String[] args) throws Exception {
String s;
System.out.println("Enter anything you want.");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
s = br.readLine();
int length = s.length();
int letters = 0;
int numbers = 0;
int spaces = 0;
for (int i = 0; i < length; i++) {
char ch;
ch = s.charAt(i);
if (Character.isLetter(ch)) {
letters++;
} else {
if (Character.isDigit(ch)) {
numbers++;
} else {
if (Character.isWhitespace(ch)) {
spaces++;
} else
continue;
}
}
}
System.out.println("Number of letters::" + letters);
System.out.println("Number of digits::" + numbers);
System.out.println("Number of white spaces:::" + spaces);
}
}

Determine how many digits and letters are in a string [closed]

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 2 years ago.
Improve this question
import java.util.Scanner;
public class digitthingy
{
public static void main(String args[])
{
Scanner s = new Scanner(System.in);
String first="";
int firstnum=0;
System.out.print("Enter a string: ");
first = s.nextLine();
firstnum = first.indexOf("1-100");
System.out.println(firstnum);
}
}
I'd like to know how many numbers there are in a certain string I entered, but I have no idea how to do it.

This looks like a job for regular expressions!
String s = "sdf234sdf234";
System.out.println(s.replaceAll("\\D", "").length());
Or perhaps your after each multiple digit number instance?
String s = "sdf234sdf234sdf23";
s = s.replaceAll("^\\D+|\\D+$", "").replaceAll("\\D+", ",");
List<String> numbers = Arrays.asList(s.split(","));
System.out.println(numbers);

String myString = "whatever123";
int count = 0;
for (int i = 0; i < myString.length(), i++) {
if (Character.isDigit(myString.charAt(i)) {
count++;
}
}
System.out.println(count);

For number of digits:
Pattern digitPattern = Pattern.compile("\\d");
Matcher digitMatcher = digitPattern.matcher("asdf 123 qwer");
int digitCount = 0;
while (digitMatcher.find())
digitCount++;
Similar for letters, only use "[a-zA-Z]" regex instead;

Count digits in string with java 8:
public long countDigits(String s) {
return s.chars().mapToObj(i -> (char) i).filter(Character::isDigit).count();
}

try this ...
public class digitthingy
{
public static void main(String args[])
{
Scanner sc = new Scanner(System.in);
String s="";
int firstnum=0;
System.out.print("Enter a string: ");
s = sc.nextLine();
int digitCount =0, charCount=0;
for(int i=0;i<s.length();i++){
if(s.charAt(i)==' ') continue;
else if((s.charAt(i) >='a' && s.charAt(i)<='z') || (s.charAt(i)>='A' && s.charAt(i)<='Z'))
charCount++;
else if(s.charAt(i) >= '0' && s.charAt(i)<='9')
digitCount++;
}
System.out.println(digitCount+ " "+ charCount);
}
}

you can use the Scanner class:
Scanner in = new Scanner(System.in);
// Reads a single line from the console
// and stores into name variable
first = s.nextLine();
And then iterate over the String:
int numbers = 0;
int letters = 0;
for(int i = 0; i < first.length(); i++)
{
if (Character.isDigit (first.charAt(i)) numbers++; // Count the digits
else if (Character.isLetter(first.charAt(i)) letters++; // Count the Letters
else{} // is not a letter and not a digit
}

Try this code I hope it will work
import java.util.Scanner;
public class CountDigitAndCharacter {
public static void main(String args[])
{
Scanner s = new Scanner(System.in);
String first="";
int firstnum=0;
System.out.print("Enter a string: ");
first = s.nextLine();
int numberCount=0,charCount=0;
for(int i=0; i<first.length();i++){
char c=first.charAt(i);
if(c=='0' || c=='1' || c=='2' || c=='3' || c=='4' || c=='5' || c=='6' || c=='7' || c=='8' || c=='9' )
++numberCount;
else
++charCount;
}
System.out.println("numberCount :-"+numberCount +" CharCount :-"+charCount);
}
}
Result:-
Enter a string: l0kesh
numberCount :-1 CharCount :-5

public class ArrayDigits
{
public static void main(String[] args)
{
String str = new String("Hey123456789234Hey");
String num = new String("0123456789");
int dig_count = 0;
for(int i=0;i<str.length();i++)
{
for(int j=0;j<num.length();j++)
{
if(str.charAt(i)==num.charAt(j))
{
dig_count++;
}
}
}
System.out.println("Total length of String:"+str.length());
System.out.println("Number of digits:"+dig_count);
System.out.println("Number of characters:"+(str.length() - dig_count));
}
}