First time using constructors - java

It compiles just fine... but throws a "java.lang.NullPointerException" error on when I try to enter the index (as an integer). I thought I already gave index an int type so I'm not sure why this happens.
I'm new to java so if you guys have any pointers on something else I need to look into or try those tips, would be appreciated as well.
import java.util.Scanner;
class LineEditor
{
public static void main (String [ ] args)
{
//variables
String myLine;
String str;
int index;
Scanner scan = new Scanner(System.in);
//creates original myLine
myLine = new String ("Computer Science");
System.out.println ("The original string of text is: " + myLine);
//variable inputs
System.out.println("Enter a string to alter myLine: ");
str = scan.next();
System.out.println("Enter an index for the string to be inserted at: ");
index = scan.nextInt();
Insert insert = new Insert(str, index);
System.out.println ("The altered string is: " + insert.strIntoMyLine());
}
}
class Insert
{
String str;
int index;
String myLine;
public Insert (String s, int i)
{
str = s;
index = i;
}
String strIntoMyLine()
{
String part1;
String part2;
part1 = myLine.substring (0, index);
part2 = myLine.substring (index);
return (part1 + str + part2);
}
}

It seems that there is nothing present in myLine.
Replace Insert insert = new Insert(str, index); with Insert insert = new Insert(str, index,myLine);.
and public Insert (String s, int i) with public Insert (String s, int I, String myLine)
Also
this.myLine = myLine; in the constructor

your constructor should be
public Insert(String s, int i, String r) {
str = s;
num = i;
myLine = r;
}
and pass value like this "Insert insert = new Insert(str, index,myLine);"

Related

Rotating a Sentence by n words

I'm am trying to update a code that I have previously written to "rotate a String." Currently my program accepts a string from keyboard input and an integer n. ex. "abcdefg", 3. Then rotates the string by n characters before returning the rotated string i.e. "efgabcd". Now for the tricky part. I'm trying to update this to do essentially the same thing but with a sentence. So the inputs would be a something like "This is an example" and an integer 3. then the output would be "is an example this." I assume splitting the sentence into an array would be my best bet; however my unfamiliarity with strings doesn't allow my to know how to go about doing this.
import java.util.*;
public class Rotate
{
public static String rotate(String s, int num)
{
int length = s.length();
String a = s.substring(0,(length-num));
String b = s.substring((length-num),length);
String c = b + a;
return c;
}
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter a string:");
String s = input.nextLine();
System.out.print("Enter the number of characters that you want to rotated to right:");
int n =input.nextInt();
String t = rotate(s, n);
System.out.println("The rotated string is "+ t);
}
}
Here's a sample solution:
int num = 3;
String str = "This is a test";
String[] strArr = str.split(" ");
int length = strArr.length;
String[] temp = Arrays.copyOfRange(strArr, length - num, length);
System.arraycopy(strArr, 0, strArr, num, length - num);
System.arraycopy(temp, 0, strArr, 0, temp.length);
str = String.join(" ", strArr);
str now contains "is a test This".
EDIT: Fixed to rotate to right.
I actually prefer #fergDEV's solution, but it can be cleaned up a bit if you're using Java 8:
int num = 3;
String str = "This is a test";
List<String> parts = Arrays.asList(str.split(" "));
Collections.rotate(parts, 3);
String.join(" ", parts);
The Collections utils are your friend :P.
public class Main {
public static String rotateSetence(final String input, final int rotation) {
final List<String> results = Arrays.asList(input.split(" "));
Collections.rotate(results, rotation);
final StringBuilder outputBuilder = new StringBuilder();
for (int i = 0; i < results.size(); i++) {
outputBuilder.append(results.get(i));
if (i != results.size() - 1)
outputBuilder.append(" ");
}
return outputBuilder.toString();
}
public static void main(String[] args) {
final String inputString = "This is an example";
final int sentenceRotation = 3;
final String expectedResult = "is an example This";
final String result = rotateSetence(inputString, sentenceRotation);
System.out.println("result " + result);
if (result.equals(expectedResult)) {
System.out.println("Passed");
} else {
System.out.println("Failed");
}
}
}
EDIT
The builder code can be replaced with string.join ... thanks to #shmosel.
final StringBuilder outputBuilder = new StringBuilder();
for (int i = 0; i < results.size(); i++) {
outputBuilder.append(results.get(i));
if (i != results.size() - 1)
outputBuilder.append(" ");
}
return outputBuilder.toString();
can be replaced with
return String.join(" ", results);
You can also make use of two for loops, such that in the first for loop you loop from num (provided by user) position to the end of the string. And in the second loop you loop from start of string until the position of num.
For above logic to work, you obviously need to split your string using space into array of strings. See below:
public static String rotate(String s, int num)
{
//split the sentence by space
String[] chunks = s.split(" ");
//use StringBuilder to build rotated string
StringBuilder builder = new StringBuilder();
//loop from position specified by user to end of array
for(int i = num; i < chunks.length; i++) {
builder.append(chunks[i] + " ");
}
//loop from start of array to position specified by user
for(int i = 0; i < num; i++) {
builder.append(chunks[i] + " ");
}
return builder.toString();
}
The input and output is shown below:
Enter a string:My name is Raf and I am super super fun guy trust me
Enter the number of characters that you want to rotated to right:2
The rotated string is : is Raf and I am super super fun guy trust me My name

Creating an object array in java using classes

I'm working on a project where I have a text file with the first line being the size of the array I'll need and then subsequent lines have course information in the following order: dept, num, title. (ex. CSC 101 Basic Computing) My code complies but when it runs the first index in the array becomes the default(i.e. nothing) and therefore the last line in the text file doesn't get stored or printed. I'm wondering how I can fix this error.
import java.util.Scanner;
import java.io.*;
public class Organizer {
public static void main(String[] args) {
Scanner fileScanner = null;
String file;
File f = null;
//Create a Do While loop in order to prompt the user for a input file
//and then continue prompting if the file entered does not exist.
do {
try {
System.out.print("What is the name of the input file? ");
Scanner inputReader = new Scanner(System.in);
file = inputReader.nextLine();
f = new File(file);
fileScanner = new Scanner(new File(file));
//Catch the exception and tell the user to try again
} catch (FileNotFoundException e) {
System.out.println("Error scanning that file, please try again.");
}
} while (!f.exists());
//Testing the Make Array Method
//System.out.print(makeArray(fileScanner));
//Testing the print Array Method
printArray(makeArray(fileScanner));
}
public static Course[] makeArray(Scanner s) {
int arraySize = s.nextInt();
String title = "";
String dept = "";
int num = 0;
Course[] a = new Course[arraySize];
for (int i = 0; i < a.length; i++) {
a[i] = new Course(dept, num, title);
String oneLine = s.nextLine();
Scanner lineReader = new Scanner(oneLine);
while (lineReader.hasNext()) {
dept = lineReader.next();
a[i].setDept(dept);
num = lineReader.nextInt();
a[i].setNum(num);
while (lineReader.hasNext()) {
title = title + lineReader.next() + " ";
}
a[i].setTitle(title);
}
title = " ";
}
return a;
}
public static void printArray(Course[] arr) {
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i].toString());
}
}
}
Here is my other class.
public static class Course {
//INSTANCE VARIABLES
private String dept = "";
private int num = 0;
private String title = "";
//CONSTRUCTORS
public Course(String dept, int num) {
this.dept = dept;
this.num = num;
}
public Course(String dept, int num, String title) {
this.dept = dept;
this.num = num;
this.title = title;
}
public Course() {
this.dept = "AAA";
this.num = 100;
this.title = "A course";
}
//SETTER AND GETTER METHODS
public void setDept(String dept) {
this.dept = dept;
}
public void setNum(int num) {
this.num = num;
}
public void setTitle(String title) {
this.title = title;
}
public String getDept() {
return this.dept;
}
public int getNum() {
return this.num;
}
public String getTitle() {
return this.title;
}
//TOSTRING METHOD
public String toString() {
return dept + " " + num + ": " + title;
}
}
Don't forget where your cursor in your Scanner is at each moment.
s.nextLine() will read the whole line and then the cursor will jump to the next line, while s.nextInt() will read one int from your line and then stay there. It won't check if this has been the last input for that line.
Just fix your code to:
int arraySize = s.nextInt();
s.nextLine();
and your code should run just fine!
(also consider changing a[i].setTitle(title); to a[i].setTitle(title.trim());, since you will always be left with a white space at the end of your title..)
nextInt method does not consume the new line character. Here is a solution that works:
public static Course[] makeArray(Scanner s){
int arraySize = s.nextInt();
String title = "";
String dept = "";
int num = 0;
Course[] a = new Course[arraySize];
s.nextLine();
for (int i = 0; i < a.length; i++){
a[i] = new Course(dept, num, title);
String oneLine = s.nextLine();
Scanner lineReader = new Scanner(oneLine);
while (lineReader.hasNext()){
dept = lineReader.next();
a[i].setDept(dept);
num = lineReader.nextInt();
a[i].setNum(num);
while (lineReader.hasNext()){
title = title + lineReader.next() + " ";
}
a[i].setTitle(title);
}
title = " ";
}
return a;
}

Single character instance from string

i was wondering how can i create a method where i can get the single instance from a string and give it a numericValue for example, if theres a String a = "Hello what the hell" there are 4 l characters and i want to give a substring from the String a which is Hello and give it numeric values. Right now in my program it gets all the character instances from string so the substring hello would get number values from the substring hell too because it also has the same characters.
my code :
public class Puzzle {
private static char[] letters = {'a','b','c','d','e','f','g','h','i', 'j','k','l','m','n','o','p','q','r','s',
't','u','v','w','x','y','z'};
private static String input;
private static String delimiters = "\\s+|\\+|//+|=";
public static void main(String[]args)
{
input = "help + me = please";
System.out.println(putValues(input));
}
//method to put numeric values for substring from input
#SuppressWarnings("static-access")
public static long putValues(String input)
{
Integer count;
long answer = 0;
String first="";
String second = "";
StringBuffer sb = new StringBuffer(input);
int wordCounter = Countwords();
String[] words = countLetters();
System.out.println(input);
if(input.isEmpty())
{
System.out.println("Sisestage mingi s6na");
}
if(wordCounter == -1 ||countLetters().length < 1){
return -1;
}
for(Character s : input.toCharArray())
{
for(Character c : letters)
{
if(s.equals(c))
{
count = c.getNumericValue(c) - 9;
System.out.print(s.toUpperCase(s) +"="+ count + ", ");
}
}
if(words[0].contains(s.toString()))
{
count = s.getNumericValue(s);
//System.out.println(count);
first += count.toString();
}
if(words[3].contains(s.toString())){
count = s.getNumericValue(s);
second += count.toString();
}
}
try {
answer = Long.parseLong(first)+ Long.parseLong(second);
} catch(NumberFormatException ex)
{
System.out.println(ex);
}
System.out.println("\n" + first + " + " + second + " = " + answer);
return answer;
}
public static int Countwords()
{
String[] countWords = input.split(" ");
int counter = countWords.length - 2;
if(counter == 0) {
System.out.println("Sisend puudu!");
return -1;
}
if(counter > 1 && counter < 3) {
System.out.println("3 sõna peab olema");
return -1;
}
if(counter > 3) {
System.out.println("3 sõna max!");
return -1;
}
return counter;
}
//method which splits input String and returns it as an Array so i can put numeric values after in the
//putValue method
public static String[] countLetters()
{
int counter = 0;
String[] words = input.split(delimiters);
for(int i = 0; i < words.length;i++) {
counter = words[i].length();
if(words[i].length() > 18) {
System.out.println("One word can only be less than 18 chars");
}
}
return words;
}
Program has to solve the word puzzles where you have to guess which digit corresponds to which letter to make a given equality valid. Each letter must correspond to a different decimal digit, and leading zeros are not allowed in the numbers.
For example, the puzzle SEND+MORE=MONEY has exactly one solution: S=9, E=5, N=6, D=7, M=1, O=0, R=8, Y=2, giving 9567+1085=10652.
import java.util.ArrayList;
public class main {
private static String ChangeString;
private static String[] ArrayA;
private static String a;
private static int wordnumber;
private static String temp;
public static void main(String[] args) {
// TODO Auto-generated method stub
a = "hello what the hell";
wordnumber = 0;
identifyint(a,wordnumber);
}
public static void identifyint (String a, int WhichWord){
ChangeString = a.split(" ")[WhichWord];
ArrayA = a.split(" ");
replaceword();
ArrayA[wordnumber] = ChangeString;
//System.out.print(ArrayA[wordnumber]);
a = "";
for(int i = 0; i<ArrayA.length;i++){
if(i==wordnumber){
a = a.concat(temp+ " ");
}
else{
a = a.concat(ArrayA[i]+" ");
}
}
System.out.print(a);
}
public static void replaceword(){
temp = "";
Character arr[] = new Character[ChangeString.length()];
for(int i = 0; i<ChangeString.length();i++){
arr[i] = ChangeString.charAt(i);
Integer k = arr[i].getNumericValue(arr[i])-9;
temp = temp.concat(""+k);
}
a = temp;
}
}
Change wordnumber to the word you want to replace each time. If this is not what you have asked for, please explain your question in more detail.

Count the number of Occurrences of a Word in a String

I am new to Java Strings the problem is that I want to count the Occurrences of a specific word in a String. Suppose that my String is:
i have a male cat. the color of male cat is Black
Now I dont want to split it as well so I want to search for a word that is "male cat". it occurs two times in my string!
What I am trying is:
int c = 0;
for (int j = 0; j < text.length(); j++) {
if (text.contains("male cat")) {
c += 1;
}
}
System.out.println("counter=" + c);
it gives me 46 counter value! So whats the solution?
You can use the following code:
String in = "i have a male cat. the color of male cat is Black";
int i = 0;
Pattern p = Pattern.compile("male cat");
Matcher m = p.matcher( in );
while (m.find()) {
i++;
}
System.out.println(i); // Prints 2
Demo
What it does?
It matches "male cat".
while(m.find())
indicates, do whatever is given inside the loop while m finds a match.
And I'm incrementing the value of i by i++, so obviously, this gives number of male cat a string has got.
If you just want the count of "male cat" then I would just do it like this:
String str = "i have a male cat. the color of male cat is Black";
int c = str.split("male cat").length - 1;
System.out.println(c);
and if you want to make sure that "female cat" is not matched then use \\b word boundaries in the split regex:
int c = str.split("\\bmale cat\\b").length - 1;
StringUtils in apache commons-lang have CountMatches method to counts the number of occurrences of one String in another.
String input = "i have a male cat. the color of male cat is Black";
int occurance = StringUtils.countMatches(input, "male cat");
System.out.println(occurance);
Java 8 version:
public static long countNumberOfOccurrencesOfWordInString(String msg, String target) {
return Arrays.stream(msg.split("[ ,\\.]")).filter(s -> s.equals(target)).count();
}
Java 8 version.
System.out.println(Pattern.compile("\\bmale cat")
.splitAsStream("i have a male cat. the color of male cat is Black")
.count()-1);
This static method does returns the number of occurrences of a string on another string.
/**
* Returns the number of appearances that a string have on another string.
*
* #param source a string to use as source of the match
* #param sentence a string that is a substring of source
* #return the number of occurrences of sentence on source
*/
public static int numberOfOccurrences(String source, String sentence) {
int occurrences = 0;
if (source.contains(sentence)) {
int withSentenceLength = source.length();
int withoutSentenceLength = source.replace(sentence, "").length();
occurrences = (withSentenceLength - withoutSentenceLength) / sentence.length();
}
return occurrences;
}
Tests:
String source = "Hello World!";
numberOfOccurrences(source, "Hello World!"); // 1
numberOfOccurrences(source, "ello W"); // 1
numberOfOccurrences(source, "l"); // 3
numberOfOccurrences(source, "fun"); // 0
numberOfOccurrences(source, "Hello"); // 1
BTW, the method could be written in one line, awful, but it also works :)
public static int numberOfOccurrences(String source, String sentence) {
return (source.contains(sentence)) ? (source.length() - source.replace(sentence, "").length()) / sentence.length() : 0;
}
using indexOf...
public static int count(String string, String substr) {
int i;
int last = 0;
int count = 0;
do {
i = string.indexOf(substr, last);
if (i != -1) count++;
last = i+substr.length();
} while(i != -1);
return count;
}
public static void main (String[] args ){
System.out.println(count("i have a male cat. the color of male cat is Black", "male cat"));
}
That will show: 2
Another implementation for count(), in just 1 line:
public static int count(String string, String substr) {
return (string.length() - string.replaceAll(substr, "").length()) / substr.length() ;
}
Why not recursive ?
public class CatchTheMaleCat {
private static final String MALE_CAT = "male cat";
static int count = 0;
public static void main(String[] arg){
wordCount("i have a male cat. the color of male cat is Black");
System.out.println(count);
}
private static boolean wordCount(String str){
if(str.contains(MALE_CAT)){
count++;
return wordCount(str.substring(str.indexOf(MALE_CAT)+MALE_CAT.length()));
}
else{
return false;
}
}
}
public class TestWordCount {
public static void main(String[] args) {
int count = numberOfOccurences("Alice", "Alice in wonderland. Alice & chinki are classmates. Chinki is better than Alice.occ");
System.out.println("count : "+count);
}
public static int numberOfOccurences(String findWord, String sentence) {
int length = sentence.length();
int lengthWithoutFindWord = sentence.replace(findWord, "").length();
return (length - lengthWithoutFindWord)/findWord.length();
}
}
This will work
int word_count(String text,String key){
int count=0;
while(text.contains(key)){
count++;
text=text.substring(text.indexOf(key)+key.length());
}
return count;
}
Replace the String that needs to be counted with empty string and then use the length without the string to calculate the number of occurrence.
public int occurrencesOf(String word)
{
int length = text.length();
int lenghtofWord = word.length();
int lengthWithoutWord = text.replace(word, "").length();
return (length - lengthWithoutWord) / lenghtofWord ;
}
Once you find the term you need to remove it from String under process so that it won't resolve the same again, use indexOf() and substring() , you don't need to do contains check length times
The string contains that string all the time when looping through it. You don't want to ++ because what this is doing right now is just getting the length of the string if it contains " "male cat"
You need to indexOf() / substring()
Kind of get what i am saying?
If you find the String you are searching for, you can go on for the length of that string (if in case you search aa in aaaa you consider it 2 times).
int c=0;
String found="male cat";
for(int j=0; j<text.length();j++){
if(text.contains(found)){
c+=1;
j+=found.length()-1;
}
}
System.out.println("counter="+c);
This should be a faster non-regex solution.
(note - Not a Java programmer)
String str = "i have a male cat. the color of male cat is Black";
int found = 0;
int oldndx = 0;
int newndx = 0;
while ( (newndx=str.indexOf("male cat", oldndx)) > -1 )
{
found++;
oldndx = newndx+8;
}
There are so many ways for the occurrence of substring and two of theme are:-
public class Test1 {
public static void main(String args[]) {
String st = "abcdsfgh yfhf hghj gjgjhbn hgkhmn abc hadslfahsd abcioh abc a ";
count(st, 0, "a".length());
}
public static void count(String trim, int i, int length) {
if (trim.contains("a")) {
trim = trim.substring(trim.indexOf("a") + length);
count(trim, i + 1, length);
} else {
System.out.println(i);
}
}
public static void countMethod2() {
int index = 0, count = 0;
String inputString = "mynameiskhanMYlaptopnameishclMYsirnameisjasaiwalmyfrontnameisvishal".toLowerCase();
String subString = "my".toLowerCase();
while (index != -1) {
index = inputString.indexOf(subString, index);
if (index != -1) {
count++;
index += subString.length();
}
}
System.out.print(count);
}}
We can count from many ways for the occurrence of substring:-
public class Test1 {
public static void main(String args[]) {
String st = "abcdsfgh yfhf hghj gjgjhbn hgkhmn abc hadslfahsd abcioh abc a ";
count(st, 0, "a".length());
}
public static void count(String trim, int i, int length) {
if (trim.contains("a")) {
trim = trim.substring(trim.indexOf("a") + length);
count(trim, i + 1, length);
} else {
System.out.println(i);
}
}
public static void countMethod2() {
int index = 0, count = 0;
String inputString = "mynameiskhanMYlaptopnameishclMYsirnameisjasaiwalmyfrontnameisvishal".toLowerCase();
String subString = "my".toLowerCase();
while (index != -1) {
index = inputString.indexOf(subString, index);
if (index != -1) {
count++;
index += subString.length();
}
}
System.out.print(count);
}}
I've got another approach here:
String description = "hello india hello india hello hello india hello";
String textToBeCounted = "hello";
// Split description using "hello", which will return
//string array of words other than hello
String[] words = description.split("hello");
// Get number of characters words other than "hello"
int lengthOfNonMatchingWords = 0;
for (String word : words) {
lengthOfNonMatchingWords += word.length();
}
// Following code gets length of `description` - length of all non-matching
// words and divide it by length of word to be counted
System.out.println("Number of matching words are " +
(description.length() - lengthOfNonMatchingWords) / textToBeCounted.length());
Complete Example here,
package com.test;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class WordsOccurances {
public static void main(String[] args) {
String sentence = "Java can run on many different operating "
+ "systems. This makes Java platform independent.";
String[] words = sentence.split(" ");
Map<String, Integer> wordsMap = new HashMap<String, Integer>();
for (int i = 0; i<words.length; i++ ) {
if (wordsMap.containsKey(words[i])) {
Integer value = wordsMap.get(words[i]);
wordsMap.put(words[i], value + 1);
} else {
wordsMap.put(words[i], 1);
}
}
/*Now iterate the HashMap to display the word with number
of time occurance */
Iterator it = wordsMap.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, Integer> entryKeyValue = (Map.Entry<String, Integer>) it.next();
System.out.println("Word : "+entryKeyValue.getKey()+", Occurance : "
+entryKeyValue.getValue()+" times");
}
}
}
public class WordCount {
public static void main(String[] args) {
// TODO Auto-generated method stub
String scentence = "This is a treeis isis is is is";
String word = "is";
int wordCount = 0;
for(int i =0;i<scentence.length();i++){
if(word.charAt(0) == scentence.charAt(i)){
if(i>0){
if(scentence.charAt(i-1) == ' '){
if(i+word.length()<scentence.length()){
if(scentence.charAt(i+word.length()) != ' '){
continue;}
}
}
else{
continue;
}
}
int count = 1;
for(int j=1 ; j<word.length();j++){
i++;
if(word.charAt(j) != scentence.charAt(i)){
break;
}
else{
count++;
}
}
if(count == word.length()){
wordCount++;
}
}
}
System.out.println("The word "+ word + " was repeated :" + wordCount);
}
}
Simple solution is here-
Below code uses HashMap as it will maintain keys and values. so here keys will be word and values will be count (occurance of a word in a given string).
public class WordOccurance
{
public static void main(String[] args)
{
HashMap<String, Integer> hm = new HashMap<>();
String str = "avinash pande avinash pande avinash";
//split the word with white space
String words[] = str.split(" ");
for (String word : words)
{
//If already added/present in hashmap then increment the count by 1
if(hm.containsKey(word))
{
hm.put(word, hm.get(word)+1);
}
else //if not added earlier then add with count 1
{
hm.put(word, 1);
}
}
//Iterate over the hashmap
Set<Entry<String, Integer>> entry = hm.entrySet();
for (Entry<String, Integer> entry2 : entry)
{
System.out.println(entry2.getKey() + " "+entry2.getValue());
}
}
}
public int occurrencesOf(String word) {
int length = text.length();
int lenghtofWord = word.length();
int lengthWithoutWord = text.replaceAll(word, "").length();
return (length - lengthWithoutWord) / lenghtofWord ;
}
for scala it's just 1 line
def numTimesOccurrenced(text:String, word:String) =text.split(word).size-1

Java: method to get position of a match in a String?

String match = "hello";
String text = "0123456789hello0123456789";
int position = getPosition(match, text); // should be 10, is there such a method?
The family of methods that does this are:
int indexOf(String str)
indexOf(String str, int fromIndex)
int lastIndexOf(String str)
lastIndexOf(String str, int fromIndex)
Returns the index within this string of the first (or last) occurrence of the specified substring [searching forward (or backward) starting at the specified index].
String text = "0123hello9012hello8901hello7890";
String word = "hello";
System.out.println(text.indexOf(word)); // prints "4"
System.out.println(text.lastIndexOf(word)); // prints "22"
// find all occurrences forward
for (int i = -1; (i = text.indexOf(word, i + 1)) != -1; i++) {
System.out.println(i);
} // prints "4", "13", "22"
// find all occurrences backward
for (int i = text.length(); (i = text.lastIndexOf(word, i - 1)) != -1; i++) {
System.out.println(i);
} // prints "22", "13", "4"
This works using regex.
String text = "I love you so much";
String wordToFind = "love";
Pattern word = Pattern.compile(wordToFind);
Matcher match = word.matcher(text);
while (match.find()) {
System.out.println("Found love at index "+ match.start() +" - "+ (match.end()-1));
}
Output :
Found 'love' at index 2 - 5
General Rule :
Regex search left to right, and once the match characters has been used, it cannot be reused.
text.indexOf(match);
See the String javadoc
Finding a single index
As others have said, use text.indexOf(match) to find a single match.
String text = "0123456789hello0123456789";
String match = "hello";
int position = text.indexOf(match); // position = 10
Finding multiple indexes
Because of #StephenC's comment about code maintainability and my own difficulty in understanding #polygenelubricants' answer, I wanted to find another way to get all the indexes of a match in a text string. The following code (which is modified from this answer) does so:
String text = "0123hello9012hello8901hello7890";
String match = "hello";
int index = text.indexOf(match);
int matchLength = match.length();
while (index >= 0) { // indexOf returns -1 if no match found
System.out.println(index);
index = text.indexOf(match, index + matchLength);
}
You can get all matches in a file simply by assigning inside while-loop, cool:
$ javac MatchTest.java
$ java MatchTest
1
16
31
46
$ cat MatchTest.java
import java.util.*;
import java.io.*;
public class MatchTest {
public static void main(String[] args){
String match = "hello";
String text = "hello0123456789hello0123456789hello1234567890hello3423243423232";
int i =0;
while((i=(text.indexOf(match,i)+1))>0)
System.out.println(i);
}
}
int match_position=text.indexOf(match);
import java.util.StringTokenizer;
public class Occourence {
public static void main(String[] args) {
String key=null,str ="my name noorus my name noorus";
int i=0,tot=0;
StringTokenizer st=new StringTokenizer(str," ");
while(st.hasMoreTokens())
{
tot=tot+1;
key = st.nextToken();
while((i=(str.indexOf(key,i)+1))>0)
{
System.out.println("position of "+key+" "+"is "+(i-1));
}
}
System.out.println("total words present in string "+tot);
}
}
I have some big code but working nicely....
class strDemo
{
public static void main(String args[])
{
String s1=new String("The Ghost of The Arabean Sea");
String s2=new String ("The");
String s6=new String ("ehT");
StringBuffer s3;
StringBuffer s4=new StringBuffer(s1);
StringBuffer s5=new StringBuffer(s2);
char c1[]=new char[30];
char c2[]=new char[5];
char c3[]=new char[5];
s1.getChars(0,28,c1,0);
s2.getChars(0,3,c2,0);
s6.getChars(0,3,c3,0); s3=s4.reverse();
int pf=0,pl=0;
char c5[]=new char[30];
s3.getChars(0,28,c5,0);
for(int i=0;i<(s1.length()-s2.length());i++)
{
int j=0;
if(pf<=1)
{
while (c1[i+j]==c2[j] && j<=s2.length())
{
j++;
System.out.println(s2.length()+" "+j);
if(j>=s2.length())
{
System.out.println("first match of(The) :->"+i);
}
pf=pf+1;
}
}
}
for(int i=0;i<(s3.length()-s6.length()+1);i++)
{
int j=0;
if(pl<=1)
{
while (c5[i+j]==c3[j] && j<=s6.length())
{
j++;
System.out.println(s6.length()+" "+j);
if(j>=s6.length())
{
System.out.println((s3.length()-i-3));
pl=pl+1;
}
}
}
}
}
}
//finding a particular word any where inthe string and printing its index and occurence
class IndOc
{
public static void main(String[] args)
{
String s="this is hyderabad city and this is";
System.out.println("the given string is ");
System.out.println("----------"+s);
char ch[]=s.toCharArray();
System.out.println(" ----word is found at ");
int j=0,noc=0;
for(int i=0;i<ch.length;i++)
{
j=i;
if(ch[i]=='i' && ch[j+1]=='s')
{
System.out.println(" index "+i);
noc++;
}
}
System.out.println("----- no of occurences are "+noc);
}
}
String match = "hello";
String text = "0123456789hello0123456789hello";
int j = 0;
String indxOfmatch = "";
for (int i = -1; i < text.length()+1; i++) {
j = text.indexOf("hello", i);
if (i>=j && j > -1) {
indxOfmatch += text.indexOf("hello", i)+" ";
}
}
System.out.println(indxOfmatch);
If you're going to scan for 'n' matches of the search string, I'd recommend using regular expressions.
They have a steep learning curve, but they'll save you hours when it comes to complex searches.
for multiple occurrence and the character found in string??yes or no
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class SubStringtest {
public static void main(String[] args)throws Exception {
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("enter the string");
String str=br.readLine();
System.out.println("enter the character which you want");
CharSequence ch=br.readLine();
boolean bool=str.contains(ch);
System.out.println("the character found is " +bool);
int position=str.indexOf(ch.toString());
while(position>=0){
System.out.println("the index no of character is " +position);
position=str.indexOf(ch.toString(),position+1);
}
}
}
public int NumberWordsInText(String FullText_, String WordToFind_, int[] positions_)
{
int iii1=0;
int iii2=0;
int iii3=0;
while((iii1=(FullText_.indexOf(WordToFind_,iii1)+1))>0){iii2=iii2+1;}
// iii2 is the number of the occurences
if(iii2>0) {
positions_ = new int[iii2];
while ((iii1 = (FullText_.indexOf(WordToFind_, iii1) + 1)) > 0) {
positions_[iii3] = iii1-1;
iii3 = iii3 + 1;
System.out.println("position=" + positions_[iii3 - 1]);
}
}
return iii2;
}
class Main{
public static int string(String str, String str1){
for (int i = 0; i <= str.length() - str1.length(); i++){
int j;
for (j = 0; j < str1.length(); j++) {
if (str1.charAt(j) != str.charAt(i + j)) {
break;
}
}
if (j == str1.length()) {
return i;
}}
return -1;
}
public static void main(String[] args)
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter the string");
String str=sc.nextLine();
System.out.println("Enter the Substring");
String str1=sc.nextLine();
System.out.println("The position of the Substring is "+string(str, str1));
}
}

Categories