10月 19, 2013
练习2
#
//从Detergent中继承产生一个新的类，覆盖scrub()并添加一个名为sterilize()的新方法。
class Cleanser{
private String s = "Cleanser";
public void append(String a ){
s+=a;
}
public void dilute(){
append(" dilute()");
}
public void apply(){
append(" apply()");
}
public void scrub(){
append(" scrub()");
}
public String toString(){
return s;
}
public static void main (String args[]){
Cleanser x = new Cleanser();
x.dilute();
x.apply();
x.scrub();
System.out.println("Cleanser.main():");
System.out.println(x);
}
}
class Detergent extends Cleanser{
public void scrub (){
append(" Detegent.scrub()");
super.scrub();
}
public void foam(){
append(" foam()");
}
public static void main (String args[]){
Detergent x = new Detergent();
x.dilute();
x.apply();
x.scrub();
x.foam();
System.out.println("Detergent.main()");
System.out.println(x);
Cleanser.main(args);
}
}
public class Main extends Detergent{
public void scrub(){
append(" Main.scrub()");
super.scrub();
}
public void sterilize(){
System.out.println("sterilize()");
}
public static void main (String args[]){
Main m = new Main();
m.apply();
m.scrub();
m.dilute();
m.foam();
System.out.println("Main.main()");
System.out.println(m);
Detergent.main(args);
m.sterilize();
}
}/*Output:
Main.main()
Cleanser apply() Main.scrub() Detegent.scrub() scrub() dilute() foam()
Detergent.main()
Cleanser dilute() apply() Detegent.scrub() scrub() foam()
Cleanser.main():
Cleanser dilute() apply() scrub()
sterilize()
*/
练习3、练习4
#
//验证：“即使不为Main（）创建构造器，编译器也会合成一个默认的构造器，该构造器将调用积累的构造器。”
class Art{
Art(){
System.out.println("Art constructor");
}
}
class Drawing extends Art{
Drawing (){
System.out.println("Drawing constructor");
}
}
public class Main extends Drawing {
public static void main (String args[]){
Main c = new Main();
}
}/*Output:
Art constructor
Drawing constructor
*/
练习5
#
//创建两个带有默认构造器（空参数）的类A和B，从A中继承产生一个名为C的新类，并在C内创建一个B类的成员，不要给C编写构造器，创建一个C类的对象并观察其结果。
class A{
A(){
System.out.println("A()");
}
}
class B{
B(){
System.out.println("B()");
}
}
class C extends A{
B b = new B();
}
public class Main{
public static void main (String args[]){
new C();
}
}/*Output:
A()
B()
*/
练习6
#
//如果不在BoardGame()中调用基类构造器，编译器将“抱怨”无法找到Game()形式的构造器。调用基类构造器必须是在导出类构造器中要做的第一件事.
class Game{
Game (int i){
System.out.println("Game constuctor");
}
}
class BoardGame extends Game{
BoardGame (int i){
super(i); //调用基类构造器，去掉这条语句会提示编译错误。
System.out.println("BoardGame constuctor");
}
}
public class Chess extends BoardGame{
Chess(){
super(11);
System.out.println("Chess constructor");
}
public static void main (String args[]){
Chess x = new Chess();
}
}
练习7
#
//修改练习5，使A和B以带参数的构造器取代默认的构造器，为C写一个构造器，并在其中执行所有的初始化。
class A{
A(int i){
System.out.println("A()"+i);
}
}
class B{
B(int i){
System.out.println("B()"+i);
}
}
class C extends A{
C(int i){
super(i);
B b = new B(i);
System.out.println("C()");
}
}
public class Main{
public static void main (String args[]){
new C(1);
}
}/*Output:
A()1
B()1
C()
*/
练习8
#
//创建一个基类，它仅有一个非默认构造器，在创建一个导出类，它带有默认构造器和非默认构造器，在导出类的构造器中调用基类的构造器。
class A{
A(int i){
System.out.println("A(i)");
}
}
class B extends A{
B(int i){
super(i);
System.out.println("B(i)");
}
}
public class Main{
public static void main (String args[]){
System.out.println("Main()");
Main m = new Main();
B b = new B(11);
}
}/*Output:
Main()
A(i)
B(i)
*/
练习9
#
//创建一个Root类，令其含有名为Component1、Component2、Component3类的各一个实例，从Root中派生一个类Stem，也含有上述各“组成部分”，所有的类都应带有可打印出类的相关信息的默认构造器。
class Component1{
Component1(){
System.out.println("Component1()");
}
}
class Component2{
Component2(){
System.out.println("Component2()");
}
}
class Component3{
Component3(){
System.out.println("Component3()");
}
}
class Root{
Component1 c1 = new Component1();
Component2 c2 = new Component2();
Component3 c3 = new Component3();
Root(){
System.out.println("Root()");
}
}
class Stem extends Root {
Component1 c1 = new Component1();
Component2 c2 = new Component2();
Component3 c3 = new Component3();
Stem (){
System.out.println("Stem()");
}
}
public class Main{
public static void main (String args[]){
new Stem();
System.out.println("Main()");
Component1 c1 = new Component1();
Component2 c2 = new Component2();
Component3 c3 = new Component3();
}
}/*Output:
Component1()
Component2()
Component3()
Root()
Component1()
Component2()
Component3()
Stem()
Main()
Component1()
Component2()
Component3()
*/
练习11
#
//修改Detergent.java，让它使用代理
class Cleanser{
private String s = "Cleanser ";
public void append(String a){
s+=a;
}
public void dilute(){
append("dilute()");
}
public void apply(){
append("apply()");
}
public void scrub(){
append("scrub()");
}
public String toString(){
return s ;
}
public static void main (String args[]){
Cleanser c = new Cleanser();
c.apply();
c.scrub();
c.dilute();
System.out.println(c);
}
}
public class Detergent {
Cleanser c1 = new Cleanser();
public void dilute(){
c1.dilute();
}
public void apply(){
c1.apply();
}
public void scrub(){
c1.scrub();
}
public static void main (String args[]){
Cleanser.main(args);
}
}/*Output:
Cleanser apply()scrub()dilute()
*/ 发现书里面那个append的用法好纠结，非要用String toString。。。
练习13
#
//创建一个类，他应带有一个 被重载的三次的方法，继承产生一个新类，并添加一个该方法的新的重载定义，展示这四个方法在导出类中是可以被使用的。
package test;
class Home {
void doh(){
System.out.println("doh()");
}
int doh(int i){
System.out.println("doh(int)");
return i;
}
char doh(char c){
System.out.println("doh(char)");
return c;
}
}
class Homehome {}
class Milhome extends Home{
void doh(Homehome h){
System.out.println("Milhome.doh()");
}
}
class Main{
public static void main (String args[]){
Milhome m=new Milhome();
m.doh();
m.doh(1);
m.doh('c');
m.doh(new Homehome());
}
}/*Output:
doh()
doh(int)
doh(char)
Milhome.doh()
*/
练习14
#
//ServiceEngine.java中给Engine添加一个service（）方法，并在main()中调用该方法
class Engine{
public void start(){}
public void rev(){}
public void stop(){}
}
class Wheel{
public void inflate(int psi){}
}
class Window{
public void rollup(){}
public void rolldown(){}
}
class Door{
public Window window = new Window();
public void open(){}
public void close(){}
}
class ServiceEngine extends Engine{
public void service(){
System.out.println("servise");
}
}
class Car{
public Engine engine = new Engine ();
public Wheel[] wheel = new Wheel[4];
ServiceEngine serviceEngine = new ServiceEngine();
public Door
left= new Door(),
right= new Door();
public Car(){
for (int i=0;i<4;i++){
wheel[i]=new Wheel();
}
}
}
public class ServicebleCar{
public static void main (String args[]){
Car car = new Car();
car.left.window.rollup();
car.left.window.rollup();
car.serviceEngine.service();
}
}/*Output:
servise
*/
练习15
#
package main.test;
public class Test {
protected void test(){
System.out.println("protected test()");
}
}
package main;
import main.test.*;
public class Main extends Test {
void Maintest(){
test();
}
public static void main (String args[]){
Main m = new Main();
Test t = new Test();
m.Maintest();
// t.test(); 编译不能通过。
}
}/*Output:
protected test()
*/
练习16
#
package main;
//创建一个名为Amphibian的类，由此继承产生一个成为Frog的类，在基类中设置适当的方法，在main（）中，创建一个Frog向上转型至Amphibian，
//然后说明所有方法都可工作。
class Amphibian{
Amphibian(){
System.out.println("Amphibian");
}
void test(){
System.out.println("Amphibian.haha");
}
}
class Frog extends Amphibian{
Frog(){
super();
System.out.println("Frog");
}
void test(){
System.out.println("Frog.test");
}
}
class Main{
public static void main (String args[]){
Amphibian a = new Frog();
a.test();
}
}/*OutPut:
Amphibian
Frog
Frog.test
*/
练习17
#
package main;
//创建一个名为Amphibian的类，由此继承产生一个成为Frog的类，在基类中设置适当的方法，在main（）中，创建一个Frog向上转型至Amphibian，
//然后说明所有方法都可工作。
class Amphibian{
Amphibian(){
System.out.println("Amphibian");
}
void test(){
System.out.println("Amphibian.haha");
}
}
class Frog extends Amphibian{
Frog(){
super();
System.out.println("Frog");
}
}
class Main{
public static void main (String args[]){
Amphibian a = new Frog();
a.test();
}
}/*OutPut:
Amphibian
Frog
Amphibian.haha
*/
练习18
#
package main;
import java.util.Random;
//创建一个含有static final域和final域的类，说明二者间的区别。
class Main{
private static Random rand = new Random();
private final int I=rand.nextInt(20);
private static final int II=rand.nextInt(20);
public static void main (String args[]){
Main m= new Main();
System.out.println("A:I="+m.I);
System.out.println("A:II="+m.II);
System.out.println();
Main m1 = new Main();
System.out.println("B:I="+m1.I);
System.out.println("B:II="+m1.II);
}
}/*Output:
A:I=10
A:II=9
B:I=12
B:II=9
*/