java insert string into another string

/**
 * @author lautturi.com
 * Java example:insert string in string 
 */

import java.util.*;

public class Lautturi {

	public static void main(String[] args) {

		String str1 = "Hello world";
		String str2 = " lautturi java";
		int insertposition = 6;
		String newStr = str1.substring(0, insertposition-1 ) 
                + str2 
                + str1.substring(insertposition -1); 
		System.out.println(newStr);
	}
}

output:

Hello lautturi java world

or

int insertposition = 5;
		String newStr = str1.substring(0, insertposition ) 
                + str2 
                + str1.substring(insertposition);