Change the characters : CharacterIterator « I18N « Java Tutorial

import java.text.CharacterIterator;
import java.text.StringCharacterIterator;

public class Main {
  public static void main(String[] argv) throws Exception {

    CharacterIterator it = new StringCharacterIterator("abcd");

    ((StringCharacterIterator) it).setText("efgh");
    char ch = it.current(); 
  }
}

13.21.CharacterIterator
	13.21.1.	Reverse a string using CharacterIterator
	13.21.2.	Iterate each characters of a string
	13.21.3.	Iterate a subset of a string
	13.21.4.	Iterating the Characters of a String
	13.21.5.	Iterate over the characters in the backward direction
	13.21.6.	Use CharacterIterator to loop through a string
	13.21.7.	Change the characters
	13.21.8.	Create an iterator on a substring (efgh)