It's not always just a naming convention -- that was not the best way to explain it. The this keyword is used to overcome shadowing. The this keyword is used to refer to the field name - if the field name and parameter name are the same. Some programmers don't like to think of a different name. So they will use name = name , but this will result in shadowing -- since both have the same name. This can be overcome by using mName = name OR this.name = name; In Android they use mName = name; whereas a Java Developer will most likely use this.name = name; The this keyword is also used when chaining constructors (aka explicit constructor invocation) -- that's when a constructor is called from another constructor. This is a keyword that an object can use to refer to itself -- that's how it is used in Java. If you would like me to explain anything else I will be happy to do so.

but Java is clever enough to know what is happening if I change the statement in the constructor to

  bar = bar;

FALSE! It compiles but it doesn't do what you think it does!

As to when to use it, a lot of it is personal preference. I like to use this in my public methods, even when it's unnecessary, because that's where the interfacing happens and it's nice to assert what's mine and what's not.

As reference, you can check the Oracle's Java Tutorials out about this.subject ;-)

http://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html