// generics/EpicBattle.java // (c)2020 MindView LLC: see Copyright.txt // We make no guarantees that this code is fit for any purpose. // Visit http://OnJava8.com for more book information. // Bounds in Java generics import java.util.*; interface SuperPower {} interface XRayVision extends SuperPower { void seeThroughWalls(); } interface SuperHearing extends SuperPower { void hearSubtleNoises(); } interface SuperSmell extends SuperPower { void trackBySmell(); } class SuperHero<POWER extends SuperPower> { POWER power; SuperHero(POWER power) { this.power = power; } POWER getPower() { return power; } } class SuperSleuth<POWER extends XRayVision> extends SuperHero<POWER> { SuperSleuth(POWER power) { super(power); } void see() { power.seeThroughWalls(); } } class CanineHero<POWER extends SuperHearing & SuperSmell> extends SuperHero<POWER> { CanineHero(POWER power) { super(power); } void hear() { power.hearSubtleNoises(); } void smell() { power.trackBySmell(); } } class SuperHearSmell implements SuperHearing, SuperSmell { @Override public void hearSubtleNoises() {} @Override public void trackBySmell() {} } class DogPerson extends CanineHero<SuperHearSmell> { DogPerson() { super(new SuperHearSmell()); } } public class EpicBattle { // Bounds in generic methods: static <POWER extends SuperHearing> void useSuperHearing(SuperHero<POWER> hero) { hero.getPower().hearSubtleNoises(); } static <POWER extends SuperHearing & SuperSmell> void superFind(SuperHero<POWER> hero) { hero.getPower().hearSubtleNoises(); hero.getPower().trackBySmell(); } public static void main(String[] args) { DogPerson dogPerson = new DogPerson(); useSuperHearing(dogPerson); superFind(dogPerson); // You can do this: List<? extends SuperHearing> audioPeople; // But you can't do this: // List<? extends SuperHearing & SuperSmell> dogPs; } }