Most of us have the tendency to write:
String s1 = "Hello";String s2 = "World";String s3 = s1 + s2;
However, the above is an expensive operation. As Strings are immutable, the code creates a new String object every time you try to alter the contents of the String.
Java has provided a variant of the String class- StringBuffer, which is mutable. StringBuffer can be used simply as:
StringBuffer sbuf (assume it is created)sbuf.append(s1);
And so on, if you are constructing a big string. Later this can be converted into a String object by the method (fatherof them all) toString().