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

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"

Answer 2

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.