Using “this” with methods (in Java)

Question

what about using \"this\" with methods in Java? Is it optional or there are situations when one needs to use it obligatory?

The only situation I have encountered is

Answer 1

http://java.sun.com/j2se/1.5.0/docs/api/java/lang/StringBuilder.html

You absolutely need this if your method needs to return the object's instance.

public class StringBuildable {
    public StringBuildable append(String text) {
        // Code to insert the string -- previously this.internalAppend(text);
        return this;
    }
}

This allows you to chain methods together in the following fashion:

String string = new StringBuildable()
    .append("hello")
    .append(' ')
    .append.("World")
    .toString()
;