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java编程思想第四版第八章习题

第一题

package net.mindview.polymorphism;
//基类-自行车
class Cycle{
    
}

//子类-单轮车
class Unicycle extends Cycle{
    
}

//子类-双轮车
class Bicycle extends Cycle{
    
}

//子类-三轮车
class Tricycle extends Cycle{
    
}

public class CycleCompetition {
    public static void ride(Cycle cycle){
        
    }
    
    public static void main(String[] args) {
        Bicycle b = new Bicycle();
        ride(b);
    }
} 你

（略）
（略）

第四题

package net.mindview.polymorphism;

import java.util.Random;

//形状
class Shape{
    public void draw(){}
    public void erase(){}
}

//圆形
class Cycle1 extends Shape {
    
    @Override
    public void draw() {
        System.out.println("draw cycle");
    }
    
    @Override
    public void erase() {
        System.out.println("erase cycle");
    }
    
}

class Square extends Shape {
    @Override
    public void draw() {
        System.out.println("draw Square");
    }
    
    @Override
    public void erase() {
        System.out.println("draw Square");
    }
}

//矩形
class Triangle extends Shape {
    @Override
    public void draw() {
        System.out.println("draw Triangle");
    }
    
    @Override
    public void erase() {
        System.out.println("draw Triangle");
    }
}

//梯形
class Trapezoid extends Shape {
    @Override
    public void draw() {
        System.out.println("draw Trapezoid");
    }
    
    @Override
    public void erase() {
        System.out.println("draw Trapezoid");
    }
}




class RandomShapeFactory {
    Random random = new Random(100);
    
    //下面画什么形状呢
    public Shape next(){
        switch(random.nextInt(4)) {
            default:
            case 0: return new Cycle1();
            case 1: return new Square();
            case 2: return new Triangle();
            case 3: return new Trapezoid();
        }
    }
}

public class Shapes {
    public static void main(String[] args) {
        Shape[] shape = new Shape[9];
        RandomShapeFactory factory = new RandomShapeFactory();
        for(int i=0; i<shape.length; i++){
            shape[i] = factory.next();
            shape[i].draw();
        }

    }

}

第五题

package net.mindview.polymorphism;
//基类-自行车
class Cycle{
    public int wheels(){
        return 0;
    }
}

//子类-单轮车
class Unicycle extends Cycle{
    public int wheels(){
        return 1;
    }
}

//子类-双轮车
class Bicycle extends Cycle{
    public int wheels(){
        return 2;
    }
}

//子类-三轮车
class Tricycle extends Cycle{
    public int wheels(){
        return 3;
    }
}

public class CycleCompetition {
    public static void ride(Cycle cycle){
        System.out.println(cycle.wheels());
    }
    
    public static void main(String[] args) {
        Bicycle b = new Bicycle();
        ride(b);
    }
}

第六题

package net.mindview.polymorphism.Music3;

import net.mindview.polymorphism.Note;

class Instrument {
    public void play(Note i){
        System.out.println("Instrument.play() ");
    }
    
    public String toString () { 
        return Instrument.class.getName(); 
    }
    
    void adjust(){System.out.println("adjust Instrument");}
    
}

class Wind extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Wind.play() ");
    }

    String what (){ return "Wind"; }
    
    void adjust(){System.out.println("adjust Wind");}
}

class Stringed extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Stringed.play() ");
    }

    String what (){ return "Stringed"; }
    
    void adjust(){System.out.println("adjust Stringed");}
}

class Brass extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Brass.play() ");
    }

    String what (){ return "Brass"; }
    
    void adjust(){System.out.println("adjust Brass");}
}

public class Music3 {
    //曲调
    public static void tune(Instrument i){
        i.play(Note.MIDDLE_C);
    }
    
    public static void tuneAll(Instrument[] i){
        for(Instrument ins: i){
            tune(ins);
        }
    }
    
    public static void main(String[] args) {
        Instrument[] i = {
                new Wind(),
                new Stringed(),
                new Brass()
        };
        tuneAll(i);
        
        Instrument t = new Instrument();
        System.out.println(t);
    }
    
    
}

第七题

package net.mindview.polymorphism.Music3;

import net.mindview.polymorphism.Note;

class Instrument {
    public void play(Note i){
        System.out.println("Instrument.play() ");
    }
    
    public String toString () { 
        return Instrument.class.getName(); 
    }
    
    void adjust(){System.out.println("adjust Instrument");}
    
}

class Wind extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Wind.play() ");
    }

    String what (){ return "Wind"; }
    
    void adjust(){System.out.println("adjust Wind");}
}

class Stringed extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Stringed.play() ");
    }

    String what (){ return "Stringed"; }
    
    void adjust(){System.out.println("adjust Stringed");}
}

class Brass extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Brass.play() ");
    }

    String what (){ return "Brass"; }
    
    void adjust(){System.out.println("adjust Brass");}
}

class Other extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Other.play() ");
    }

    String what (){ return "Other"; }
    
    void adjust(){System.out.println("adjust Other");}
}

public class Music3 {
    //曲调
    public static void tune(Instrument i){
        i.play(Note.MIDDLE_C);
    }
    
    public static void tuneAll(Instrument[] i){
        for(Instrument ins: i){
            tune(ins);
        }
    }
    
    public static void main(String[] args) {
        Instrument[] i = {
                new Wind(),
                new Stringed(),
                new Brass(),
                new Other()
        };
        tuneAll(i);
        
        Instrument t = new Instrument();
        System.out.println(t);
    }
    
    
}

第八题

package net.mindview.polymorphism.Music3;

import java.util.Random;

import net.mindview.polymorphism.Note;

class Instrument {
    public void play(Note i){
        System.out.println("Instrument.play() ");
    }
    
    public String toString () { 
        return Instrument.class.getName(); 
    }
    
    void adjust(){System.out.println("adjust Instrument");}
    
}

class Wind extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Wind.play() ");
    }

    String what (){ return "Wind"; }
    
    void adjust(){System.out.println("adjust Wind");}
}

class Stringed extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Stringed.play() ");
    }

    String what (){ return "Stringed"; }
    
    void adjust(){System.out.println("adjust Stringed");}
}

class Brass extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Brass.play() ");
    }

    String what (){ return "Brass"; }
    
    void adjust(){System.out.println("adjust Brass");}
}

class Other extends Instrument {
    @Override
    public void play(Note i) {
        System.out.println("Other.play() ");
    }

    String what (){ return "Other"; }
    
    void adjust(){System.out.println("adjust Other");}
}

class RandomInstrumentFactory {
    Random rand = new Random(100);
    public Instrument next(){
        switch(rand.nextInt(4)){
            default:
            case 0: return new Wind();
            case 1: return new Stringed();
            case 2: return new Brass();
            case 3: return new Other();
        }
    }
}

public class Music3 {
    //曲调
    public static void tune(Instrument i){
        i.play(Note.MIDDLE_C);
    }
    
    public static void tuneAll(Instrument[] i){
        for(Instrument ins: i){
            tune(ins);
        }
    }
    
    public static void main(String[] args) {
        RandomInstrumentFactory factory = new RandomInstrumentFactory();
        Instrument[] instruments = new Instrument[10];
        for(int i=0; i<instruments.length; i++){
            instruments[i] = factory.next();
        }
        tuneAll(instruments);
        
        Instrument t = new Instrument();
        System.out.println(t);
    }
    
    
}

第九题

package net.mindview.polymorphism;

//啮(nie四声)齿动物
class Rodent{
    void say(){System.out.println("hi,我是 Rodent");}
}

//老鼠
class Mouse extends Rodent{
    void say(){System.out.println("hi,我是 Mouse");}
}

//鼹鼠
class Gerbil extends Rodent{
    void say(){System.out.println("hi,我是 Gerbil");}
}

//大颊鼠
class Hamster extends Rodent{
    void say(){System.out.println("hi,我是 Hamster");}
}


//啮(nie四声)齿动物大家族
public class RodentHome {
    public static void instroduce(Rodent rodent){
        rodent.say();
    }
    
    public static void instroduceAll(Rodent[] rodents){
        for(Rodent r: rodents){
            instroduce(r);
        }
    }
    
    public static void main(String[] args) {
        Rodent[] rodents = {
                new Mouse(),
                new Gerbil(),
                new Hamster()
        };
        instroduceAll(rodents);
    }
}

第十题

package net.mindview.polymorphism;

class Base{
    public void method1(){
        System.out.println("method1");
        method2();
    }
    
    public void method2(){
        System.out.println("Base method2");
    }
}

class Child extends Base{
    @Override
    public void method2() {
        System.out.println("Child method2");
    }
}

public class Test10 {
    
    public static void up(Base b){
        b.method1();
    }
    
    public static void main(String[] args) {
        Child c = new Child();
        up(c);

    }
}

第十三题

package net.mindview.polymorphism;
import static net.mindview.util.Print.*;
//这是一个共享类
class Shared {
    private int refCount = 0;
    private static long counter = 0;
    private final long id = counter++;
    
    public Shared(){
        println("Creating "+this);
    }
    
    public void addRef(){
        refCount ++;
    }
    
    protected void dispose(){
        if(--refCount ==0){
            println("Disposing " + this);
        }
    }
    
    @Override
    public String toString() {
        return "Shared " + id;
    }
    
    @Override
    protected void finalize() throws Throwable {
        if(refCount != 0){
            println("Error, 引用计数不为0");
        }
        super.finalize();
    }
}

//组成类
class Composing{
    private Shared shared;
    private static long counter = 0;
    private final long id = counter ++;
    
    public Composing(Shared shared){
        println("Creating "+ this);
        this.shared = shared;
        shared.addRef();
    }
    
    protected void dispose() {
        println("dispose " + this);
        shared.dispose();
    }
    @Override
    public String toString() {
        return "Composing " + id;
    }
    
    
}

//引用计数
public class ReferenceCounting {
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Shared shared = new Shared();
        Composing[] composing = {
                new Composing(shared),
                new Composing(shared),
                new Composing(shared),
                new Composing(shared),
                new Composing(shared),
                new Composing(shared)
        };
        for(Composing c:composing){
            c.dispose();
        }
    }
}

第十六题

package net.mindview.polymorphism;

class AlertStatus {
    @Override
    public String toString() {
        return "AlertStatus";
    }
}

class StartStatus extends AlertStatus {
    @Override
    public String toString() {
        return "StartStatus";
    }
}

class EndStatus extends AlertStatus {
    @Override
    public String toString() {
        return "EndStatus";
    }
}

class PauseStatus extends AlertStatus {
    @Override
    public String toString() {
        return "PauseStatus";
    }
}

class Music4 {
    AlertStatus as = new StartStatus();
    
    public void pause(){
        as = new PauseStatus();
    }
    
    public void end(){
        as = new EndStatus();
    }
    
    public void currentStatus(){
        System.out.println(as);
    }
}


public class Starship {

    public static void main(String[] args) {
        Music4 m = new Music4();
        m.currentStatus();
        m.pause();
        m.currentStatus();
        m.end();
        m.currentStatus();
    }
}

第十七题

package net.mindview.polymorphism;
//基类-自行车
class Cycle{
    public int wheels(){
        return 0;
    }
}

//子类-单轮车
class Unicycle extends Cycle{
    public int wheels(){
        return 1;
    }
    
    public void balance(){
        System.out.println("Unicycle balance");
    }
}

//子类-双轮车
class Bicycle extends Cycle{
    public int wheels(){
        return 2;
    }
    public void balance(){
        System.out.println("Bicycle balance");
    }
}

//子类-三轮车
class Tricycle extends Cycle{
    public int wheels(){
        return 3;
    }
}

public class CycleCompetition {
    public static void ride(Cycle cycle){
        System.out.println(cycle.wheels());
    }
    
    public static void main(String[] args) {
        Cycle[] cycle = {
                new Cycle(),
                new Unicycle(),
                new Bicycle(),
                new Tricycle()
        };
        //((Cycle)cycle[0]).balance();//编译不通过
        ((Unicycle)cycle[1]).balance();
        ((Bicycle)cycle[2]).balance();
    }
}

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原文地址：https://www.cnblogs.com/ITPower/p/8532997.html