Interface as a method's parameter

Question

I have a problem with naming following situation

{...}

X.a;
a.addListener( new ListenerForX(){
// some interface methods
});

{...}

It is the same as:

{...} 
X.a;
a.addListener( new XListener());
{...} 
private class XListener implements ListenerForX{
//some methods
}

How is it called?

Answer 1

The first code example is called anonymous inner class.

Both examples are valid in Java. The method is just interested in ListenerForX and doesn't care about the implementation thereof.

Answer 2

The first one is an anonymous inner class.

Say you have an interface Walkable with doWalk () ,

For a method that takes in a Walkable instance you could write something like .

takeForaWalk(new Walkable() {
 void doWalk() {
 //Impl
}}
)