add string to string java code example

Example 1: insert string in string java

String newString = originalString.substring(0, index + 1) 
                           + stringToBeInserted 
                           + originalString.substring(index + 1);

Example 2: java concatenate strings

public class Concat {
    String cat(String a, String b) {
        a += b;
        return a;
    }
}