Functional Programming Techniques: Functional Interfaces, Streams, Parallel Collections - Java - page 335

/** An Acceptor accepts some elements from a Collection */
public

public interface interface CameraAcceptor CameraAcceptor {

boolean boolean choose ( Camera c );

}

Now the search application provides a method:

public public List < Camera > search ( CameraAcceptor acc );

which we can call with code like this (assuming you're comfortable with anonymous inner
classes):

results = searchApp . search ( new new CameraAcceptor () {

public public boolean boolean choose ( Camera c ) {

return return c . isIlc () && c . getPrice () < 500 ;

}

}

Or, if you were not comfortable with anonymous inner classes, you might have to type

class class MyIlcPriceAcceptor MyIlcPriceAcceptor implements implements CameraAcceptor {

public public boolean boolean choose ( Camera c ) {

return return c . isIlc () && c . getPrice () < 500 ;

}

}
CameraAcceptor myIlcPriceAcceptor = nwq MyIlcPriceAcceptor ();
results = searchApp . search ( myIlcPriceAcceptor );

That's really a great deal of typing just to get one method packaged up for sending into the
search engine. Java's support for lambda expressions or Closures was argued about for many
years (literally) before the experts agreed on how to do it. And the result is staggeringly
simple. One way to think of Java lambda expressions is that each one is just a method that
implements a functional interface . With lambda expressions, you can rewrite the preceding
as just:

results = searchApp . search ( c -> c . isIlc () && c . getPrice () < 500 );