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

Question

String match = "hello";
String text = "0123456789hello0123456789";

int position = getPosition(match, text); // should be 10, is there such a method?

Answer 1

Use string.indexOf to get the starting index.

Answer 2

text.indexOf(match);

See the String javadoc

Answer 3

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; ) {
    System.out.println(i);
} // prints "4", "13", "22"

// find all occurrences backward
for (int i = text.length(); (i = text.lastIndexOf(word, i - 1)) != -1; ) {
    System.out.println(i);
} // prints "22", "13", "4"

Answer 4

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);
    }
}