Java-Java编程思想第四版 第十章 练习

练习1：

/* Write a class named Outer that contains an inner class named Innet.
* Add a method to Outer that returns an object of type Inner. In main(),
* create and initialize a reference to an Inner.
*/

import static net.mindview.util.Print.*;
class Outer{
Inner out(){return new Inner();}
class Inner{
void in(){print("it's inner class");}
}
}
public class Ja10_1_1{
public static void main(String[] args){
Outer ou=new Outer();
Outer.Inner in=ou.out();
in.in();
}
}

练习2：/* Create a class that holds a String, and has a toString() method that* displays this String. Add several instances of your new class to a* Sequence ojbect, then display them.*/

import static net.mindview.util.Print.*;

interface Selector{
boolean end();
void next();
Object current();
}
class Word{
private  String word;// this "word" can't be static. Or, the value can't be assigned!
public Word(String s){word=s;}
public String toString(){return word;}//toString must be public
}
public class Ja10_2_2{
private Object[] aa;//it must be Object
private static int i=0;
private static int j=0;
public Ja10_2_2(int size){aa=new Object[size];} //the size of Number array must be defined here.
private class SequenceSelector implements Selector{
public Object current(){return aa[j];}
public void next(){j++;}
public boolean end(){if(j<aa.length) return true; else{j=0;return false;} }
}
Selector selector(){return new SequenceSelector();}
void add(Object s){//it must be Object
if(i<aa.length){
aa[i]=s;
print(aa[1]);
++i;
}
}
public static void main(String[] args){
Ja10_2_2 ja=new Ja10_2_2(3);
ja.add(new Word("aaaa"));
ja.add(new Word("bbbb"));
ja.add(new Word("cccc"));
Selector sel=ja.selector();
while(sel.end()){
print(sel.current());
sel.next();
}
}
}

PS：(1)变量aa必须定义成Object，这样导入参数时Word类可以向上转型成Object，使toString（）可以工作(2)toString()方法必须是public的(3)String word变量不能是static的，否则当它从aaaa变到cccc，指向它的a[0]~a[2]的数组的值会全部变成cccc！(4)数组的大小必须事前定义好（Ja-22-）,否则会wei'l练习3：

/* Modify Exercise 1 so that Outer has a private String field (initialized
* by the constructor), and Inner has a toString() that displays this field.
* Create an object of type Inner and display it.
*/

import static net.mindview.util.Print.*;

class Outer{
private String ss;
Inner out(){ss="dsaf"; return new Inner();}
class Inner{
public String toString(){return ss;}
void in(){print("it's inner class");}
}
}
public class Ja10_2_3{
public static void main(String[] args){
Outer ou=new Outer();
Outer.Inner in=ou.out();
print(in);
}
}

练习4：import static net.mindview.util.Print.*;interface Selector {boolean end();Object current();void next();Ja10_3_4 infer();//!}public class Ja10_3_4 {private Object[] items;private int next = 0;public Ja10_3_4(int size) { items = new Object[size]; }public void add(Object x) {if(next < items.length)items[next++] = x;}private class SequenceSelector implements Selector {private int i = 0;public boolean end() { return i == items.length; }public Object current() { return items[i]; }public void next() { if(i < items.length) i++; }public Ja10_3_4 infer(){return Ja10_3_4.this;}//!}public Selector selector() {return new SequenceSelector();}public void outerInferred(){print("Ja10_3_4 inferred.");}public static void main(String[] args) {Ja10_3_4 sequence = new Ja10_3_4(10);for(int i = 0; i < 10; i++)sequence.add(Integer.toString(i));Selector selector = sequence.selector();selector.infer().outerInferred();//!while(!selector.end()) {System.out.print(selector.current() + " ");selector.next();}}}PS://!处，为新增代码练习5：import static net.mindview.util.Print.*;class Outer{class Inner{Inner(){print("adsf");}}}public class Ja10_3_5{public static void main(String[] args){Outer ou=new Outer();Outer.Inner in=ou.new Inner();}}

练习6：import net.mindview.simple.*;/*interface Ja10_4_6a{void f();}*//*class Ja10_4_6b{class Ja10_4_6c implements Ja10_4_6a{public void f(){System.out.println("It's Ja10_4_6b");}}}*/public class Ja10_4_6 extends Ja10_4_6b{public static void main(String[] args){Ja10_4_6b ja=new Ja10_4_6b();Ja10_4_6a jac=ja.new Ja10_4_6c();jac.f();}}练习7：import static net.mindview.util.Print.*;class Ja10_4_7a{private int i=5;private void outMethod(){print("It's method of outer");}class Ja10_4_7b{void f(){i=3;print(i);}void inMethod(){outMethod();}}}public class Ja10_4_7{public static void main(String[] args){Ja10_4_7a jaa=new Ja10_4_7a();Ja10_4_7a.Ja10_4_7b jab=jaa.new Ja10_4_7b();jab.f();jab.inMethod();}}

练习9：/* Create an interface with at least one method, and implement that* interface by defining an inner class within a method, which returns a* reference to your interface.*/import static net.mindview.util.Print.*;interface A{void f();}public class Ja10_5_9{A outMethod1(){class B implements A{public void f(){print("it's B implements A.f()");}}return new B();}public static void main(String[] args){Ja10_5_9 ja=new Ja10_5_9();A a=ja.outMethod1();a.f();}}练习11：/* Create a private inner class that implements a public interface.* Write a method that returns a reference to an instance of the private* inner class, upcast to the interface. Show that the inner class is* completely hidden by trying to downcast to it.*/import static net.mindview.util.Print.*;interface A{void f();}/*public class Ja10_5_11{A forReturn(){private class B implements A{public void f(){print("It's Ja10_5_11.B.f()");}}return new B();}public static void main(String[] args){Ja10_5_11 ja=new Ja10_5_11();A a=ja.forReturn();a.f();}}*/class C{private class B implements A{public void f(){print("It's Ja10_5_11.B.f()");}}A forReturn(){return new B();}}public class Ja10_5_11{public static void main(String[] args){C c=new C();A a=c.forReturn();a.f();//!B b=(B)a;//!b.f();}}

PS: 方法内部的内部类，不能设成private？练习12：/* Repeat Exercise 7 using an anonymous inner class.* (Exercise 7: Create a class with a private field and a private method.* Create an inner class with a method that modifies the outer-class field

* and calls the outer class method. In a second outer-class method, create
* an object of the inner class and call its method, then show the effect on
* the outer-class object.)
*/
import static net.mindview.util.Print.*;
interface  Ja10_4_7b{
void f();
void inMethod();
}

class Ja10_4_7a{
private int i=5;
private void outMethod(){print("It's method of outer");}
Ja10_4_7b bb(){
return new Ja10_4_7b(){
private int j=5;
private void bb(){print(j);}
{print(j);}
public void f(){i=3;print(i);}
public void inMethod(){outMethod();}
};
}
}
public class Ja10_6_12{
public static void main(String[] args){
Ja10_4_7a jaa=new Ja10_4_7a();
jaa.bb();
}
}

练习13：/* Repeat Exercise 9 using an anonymous inner class.* (Exercise 9: Create an interface with at least one method, and implement* that interface by defining an inner class within a method, which returns* a reference to your interface.)*/import static net.mindview.util.Print.*;interface A{void f();}public class Ja10_6_13{A outMethod1(){return new A(){{print("it's inner class A");}public void f(){print("it's B implements A.f()");}};}public static void main(String[] args){Ja10_6_13 ja=new Ja10_6_13();A a=ja.outMethod1();a.f();}}

练习14：/* Modify interfaces/HorrorShow.java to implement DangerousMonster and* Vampire using anonymous classes.*/interface Monster {void menace();}interface DangerousMonster extends Monster {void destroy();}interface Lethal {void kill();}interface Vampire extends DangerousMonster, Lethal {void drinkBlood();}public class Ja10_6_14 {static void u(Monster b) { b.menace(); }static void v(DangerousMonster d) {d.menace();d.destroy();}static void w(Lethal l) { l.kill(); }DangerousMonster monster(){return new DangerousMonster(){public void menace() {}public void destroy() {}};}Vampire vampire(){return new Vampire(){public void menace() {}public void destroy() {}public void kill() {}public void drinkBc010lood() {}};}public static void main(String[] args) {Ja10_6_14 ja=new Ja10_6_14();DangerousMonster barney =ja.monster();u(barney);v(barney);Vampire vlad =ja.vampire();u(vlad);v(vlad);w(vlad);}}练习15：/* Create a class with a non-default constructor and no default constructor.* Create a second class that has a method that returns a reference to an* object of the first class. Create the object that you return by making an* anonymous inner class that inherits from the first class.*/import static net.mindview.util.Print.*;abstract class A{void a(int i){}}class C extends A{}class B{A returnInner(final int i){return new C(){//private int ii=i;void a(int ii){print("It's B.C.a("+ii+")");}};}}public class Ja10_6_15{public static void main(String[] args){B b=new B();b.returnInner(5).a(8);}}

练习16：/* Modify the solution to Exercise 18 from the Interfaces chapter to use* anonymous inner classes.* (Exercise 18, Interface: Create a Cycle interface, with implementations* Unicycle, Bicycle and Tricycle. Create factories for each type of Cycle,* and code that uses these factories.*/import static net.mindview.util.Print.*;interface Cycle{void produce();}interface CycleFactory{Cycle getCycle();}class Unicycle implements Cycle{public void produce(){print("it's Unicycle");}public static CycleFactory factory=new CycleFactory(){public Cycle getCycle(){return new Unicycle();}};}class Bicycle implements Cycle{public void produce(){print("it's Bicycle");}public static CycleFactory factory=new CycleFactory(){public Cycle getCycle(){return new Bicycle();}};}class Tricycle implements Cycle{public void produce(){print("it's Tricycle");}public static CycleFactory factory=new CycleFactory(){public Cycle getCycle(){return new Tricycle();}};}public class Ja10_6_16{static void make(CycleFactory cf){Cycle c=cf.getCycle();c.produce();}public static void main(String[] args){make(Unicycle.factory);make(Bicycle.factory);make(Tricycle.factory);}}练习18：/* Create a class containing a nested class. In main(), create an instance of* the nested class.*/class C{class D{}}public class Ja10_6_18{static class B{}class A{}public static void main(String[] args){B b=new B();//!A a=new A();Ja10_6_18 ja=new Ja10_6_18();A a=ja.new A();C c=new C();C.D d=c.new D();}}

练习19：/* Create a class containing an inner class that itself contains an inner* class. Repeat this using nested classes. Note the names of the .class files* produced by the compiler.*/import static net.mindview.util.Print.*;public class Ja10_6_19{private static class A{private static class B{void f(){print("It's Ja10_6_19.A.B");}}}public static void main(String[] args){A.B b=new A.B();b.f();}}

练习20：/* Create an interface containing a nested class. Implement this interface and* create an instance of the nested class.*/import static net.mindview.util.Print.*;public interface Ja10_7_20{void f();class B implements Ja10_7_20{public void f(){print("sds");}public static void main(String[] args){B b=new B();b.f();}}}

练习21：/* Create an interface that contains a nested class that has a static method that* calls the methods of your interface and displays the results. Implement your* interface and pass an instance of your implementation to the method.*/import static net.mindview.util.Print.*;interface A{public void f();public static class B{static void ff(Ja10_7_21 i){print(i);}}}public class Ja10_7_21 implements A{public void f(){print("sooos");}public static void main(String[] args){Ja10_7_21 ja=new Ja10_7_21();A.B.ff(ja);}}

PS:知道了调用方法ff()，只需引用A.B.ff()。B和f()都是静态的练习22：interface Selector {boolean end();Object current();void next();}public class Ja10_8_22{private Object[] items;private int next = 0;public Ja10_8_22(int size) { items = new Object[size]; }public void add(Object x) {if(next < items.length)items[next++] = x;}private class SequenceSelector{Selector forwardSelector(){return new Selector() {private int i = 0;public boolean end() { return i == items.length; }public Object current() { return items[i]; }public void next() { if(i < items.length) i++; }};}Selector reverseSelector(){return new Selector() {private int i = items.length-1;public boolean end() { return i == -1; }public Object current() { return items[i]; }public void next() { if(i > -1) i--; }//[0,length-1]};}}public Selector selector(int i) {if(i==1){return new SequenceSelector().forwardSelector();}else{return new SequenceSelector().reverseSelector();}}public static void main(String[] args) {Ja10_8_22 sequence = new Ja10_8_22(10);for(int i = 0; i < 10; i++)sequence.add(Integer.toString(i));Selector selector = sequence.selector(0);while(!selector.end()) {System.out.print(selector.current() + " ");selector.next();}}}

练习23：/* Create an interface U with three methods. Create a class A with a method that* produces a reference to a U by building an anonymous inner class. Create a second* class B that contains an array of U. B should have one method that accepts and* stores a reference to U in the array, a second method that sets a reference in* the array (specified by the method argument) to null, and a third method that* moves through the array and calls the methods in U. In main, create a group of A* objects and a single B. Fill the B with U references produced by the A objects.* Use the B to call back into all the A objects. Remove some of the U references* from the B.*/import static net.mindview.util.Print.*;interface U{void a();void b();void c();}class A{U aA(){return new U(){public void a(){print("A.a()");}public void b(){print("A.b()");}public void c(){print("A.c()");}};}}class B{private U[] us;B(int i){us=new U[i];}void addU(U u, int i){us[i]=u;}void eraseU(int i){us[i]=null;}void testUs(){for(U u:us){u.a(); u.b(); u.c();}}}public class Ja10_8_23{public static void main(String[] args){B bb=new B(5);for(int i=0;i<5;i++){A aa=new A();bb.addU(aa.aA(),i);}//bb.testUs();bb.eraseU(3);bb.eraseU(1);bb.testUs();}}练习24：/* In GreenhouseControls.java, add Event inner classes that turn fans on and* off. Configure GreenhouseController.java to use these new Event objects.*/import innerclasses.*;import innerclasses.controller.*;public class Ja10_8_24 {public static void main(String[] args) {GreenhouseControls gc = new GreenhouseControls();// Instead of hard-wiring, you could parse// configuration information from a text file here:gc.addEvent(gc.new Bell(900));Event[] eventList = {gc.new ThermostatNight(0),gc.new LightOn(200),gc.new LightOff(400),gc.new WaterOn(600),gc.new WaterOff(800),gc.new ThermostatDay(0),gc.new FanOn(0),gc.new FanOff(0)};gc.addEvent(gc.new Restart(2000, eventList));gc.addEvent(new GreenhouseControls.Terminate(2000));gc.run();}} /* Output*///:~

练习25：/* Inherit from GreenhouseControls in GreenhouseControls.java to add Event* inner classes that turn water mist generators on and off. Write a new* version of GreenhouseController.java to use these new Event objects.*/import innerclasses.*;import innerclasses.controller.*;class GreenhouseControls2 extends GreenhouseControls{private boolean jet=false;public class JetOn extends Event{public JetOn(long delayTime){super(delayTime);}public void action(){jet=true;}public String toString(){return "Jet is on.";}}public class JetOff extends Event{public JetOff(long delayTime){super(delayTime);}public void action(){jet=false;}public String toString(){return "Jet is false.";}}}public class Ja10_8_25 {public static void main(String[] args) {GreenhouseControls2 gc = new GreenhouseControls2();// Instead of hard-wiring, you could parse// configuration information from a text file here:gc.addEvent(gc.new Bell(900));Event[] eventList = {gc.new ThermostatNight(0),gc.new LightOn(200),gc.new LightOff(400),gc.new WaterOn(600),gc.new WaterOff(800),gc.new ThermostatDay(0),gc.new FanOn(0),gc.new FanOff(0),gc.new JetOn(0),gc.new JetOff(0)};gc.addEvent(gc.new Restart(2000, eventList));gc.addEvent(new GreenhouseControls.Terminate(2000));gc.run();}}

练习26：/* Create a class with an inner class that has a non-default constructor* (one that takes arguments). Create a second class with an inner* class that inherits from the first inner class.*/import static net.mindview.util.Print.*;class A{class inA{inA(){print("A.inA()");}}}class B{class inB extends A.inA{inB(A a){a.super();}}}public class Ja10_8_26{public static void main(String[] args){A a=new A();B b=new B();B.inB inb=b.new inB(a);}}