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- 创建两个带有默认构造器（空参数列表）的类A和类B。从A中继承产生一个名为C的新，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。
package net.mindview.reusing; public class A {
public A(){
System.out.println("A");
}
} package net.mindview.reusing; public class B {
public B(){
System.out.println("B");
}
} package net.mindview.reusing; public class C extends A {
B b = new B();
public static void main(String[] args) {
C c = new C(); }
} - (略)
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- 创建一个Root类，令其含有名为Component1、Component 2、Component3的类的各一个实例（这些也由你写）。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
package net.mindview.reusing; public class Root {
private Component1 c1 = new Component1();
private Component2 c2 = new Component2();
private Component3 c3 = new Component3(); public Root() {
System.out.println("Root");
System.out.println("Root->c1");
System.out.println("Root->c2");
System.out.println("Root->c3");
} } package net.mindview.reusing; public class Component1 { public Component1() {
System.out.println("Component1");
} } package net.mindview.reusing; public class Component2 { public Component2() {
System.out.println("Component2");
} } package net.mindview.reusing; public class Component3 { public Component3() {
System.out.println("Component3");
} } package net.mindview.reusing; public class Stem extends Root { private Component1 c1 = new Component1();
private Component2 c2 = new Component2();
private Component3 c3 = new Component3();
public Stem() {
System.out.println("RootChild");
System.out.println("Stem->c1");
System.out.println("Stem->c2");
System.out.println("Stem->c3");
} public static void main(String[] args) {
Root t = new Stem(); } } - （略）可参考总结中的第5点，使用代理模式。
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- 在Car.java中给Engine添加一个service(),并在main()中调用该方法。
package net.mindview.reusing; class Engine {
public void start(){}
public void rev(){}
public void stop(){}
public void Service() {
System.out.println("Engine.Service");
}
} 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(){}
} public class Car {
public Engine engine = new Engine();
public Wheel[] wheels = new Wheel[];
public Door left = new Door(),right = new Door();
public Car(){
for(int i=;i<; i++){
wheels[i] = new Wheel();
}
}
public static void main(String[] args) {
Car car = new Car();
car.left.window.rollup();
car.wheels[].inflate();
car.engine.Service();
}
} - (略)
- 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
package net.mindview.reusing; //两栖动物
class Amphibian{
//交配
public void mating(Amphibian amphibian){
System.out.println("两栖动物交配");
}
}
//青蛙
public class Frog extends Amphibian{ public static void main(String[] args) {
Frog frog = new Frog();
frog.mating(frog); }
} - 修改练习16，使Frog覆盖基类中方法的定义。请留心main中都发生了什么
package net.mindview.reusing; //两栖动物
class Amphibian{
//交配
public void mating(Amphibian amphibian){
System.out.println("两栖动物交配");
}
}
//青蛙
public class Frog extends Amphibian{
public void mating(Frog frog){
System.out.println("青蛙交配");
}
public static void main(String[] args) {
Frog frog = new Frog();
frog.mating(frog); }
} - （略）
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