How to Find All Matches in String Java - Simple Guide

In Java, you can find all matches in a string by using Pattern and Matcher classes. Compile a regex with Pattern.compile(), create a Matcher with pattern.matcher(input), then use matcher.find() in a loop to get each match.

Syntax

To find all matches in a string, use these steps:

• Pattern.compile(regex): Creates a pattern object from your regular expression.
• pattern.matcher(inputString): Creates a matcher to search the input string.
• matcher.find(): Finds the next match each time it is called, returning true if found.
• matcher.group(): Returns the matched substring.

java

Pattern pattern = Pattern.compile("your-regex");
Matcher matcher = pattern.matcher("your input string");
while (matcher.find()) {
    String match = matcher.group();
    // process match
}

Example

This example finds all words starting with a capital letter in a sentence and prints them one by one.

java

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class FindAllMatches {
    public static void main(String[] args) {
        String text = "Java is Fun. Learning Java is rewarding.";
        Pattern pattern = Pattern.compile("\\b[A-Z][a-z]*\\b");
        Matcher matcher = pattern.matcher(text);

        while (matcher.find()) {
            System.out.println(matcher.group());
        }
    }
}

Output

Java
Fun
Learning
Java

Common Pitfalls

Common mistakes when finding matches include:

• Using matcher.group() before calling matcher.find(), which causes errors.
• Not looping with matcher.find() and only getting the first match.
• Using incorrect regex patterns that do not match the intended text.

Always call matcher.find() in a loop and then get the match with matcher.group().

java

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class WrongWay {
    public static void main(String[] args) {
        String text = "Test 123 Test 456";
        Pattern pattern = Pattern.compile("Test");
        Matcher matcher = pattern.matcher(text);

        // Wrong: calling group() before find()
        // System.out.println(matcher.group()); // Throws IllegalStateException

        // Right way:
        while (matcher.find()) {
            System.out.println(matcher.group());
        }
    }
}

Output

Test
Test

Quick Reference

Remember these key points when finding all matches in Java strings:

• Use Pattern.compile() to create a regex pattern.
• Create a Matcher from the pattern and input string.
• Loop with matcher.find() to get each match.
• Use matcher.group() to access the matched text.

Key Takeaways

Use Pattern and Matcher classes to find all matches in a string.

Call matcher.find() repeatedly in a loop to get each match.

Access the matched text with matcher.group() after find().

Avoid calling matcher.group() before matcher.find() to prevent errors.

Write correct regex patterns to match the desired text.