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Java面向对象经典案例10个.doc

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1 class Anthropoid { //类人猿 private int n=100; void crySpeak(String s) { System.out.println(s); } } class People extends Anthropoid { void computer(int a,int b) { int c=a*b; System.out.println(c); } void crySpeak(String s) { System.out.println("**"+s+"**"); } } public class Monkey { public static void main(String args[]) { Anthropoid monkey=new People(); //monkey 是 People 对象的上转型对象 //monkey.computer(10,10); //非法 monkey.crySpeak("我喜欢这个运动"); People people=(People)monkey; //把上转型对象强制转化为子类的对象 people.computer(10,10); } } 2
class ManyArea{ public double area(double radius){ return Math.PI*radius*radius; } public double area(double len,double width){ return len*width; } public double area(int len,int width){ return len*width; } public double area(double len,double width,double height){ return len*width*height; } } public class OverLoad{ public static void main(String args[]){ ManyArea ob=new ManyArea(); System.out.println("半径为 3.0 的圆的面积:"+ob.area(3.0)); System.out.println("长 2.0、宽 3.0 的面积:"+ob.area(2.0,3.0)); System.out.println("长 2、宽 3 的面积:"+ob.area(2,3)); System.out.println("立方体的面积:"+ob.area(2.0,3.0,4.0)); } } 3 class Animal { public void shout() { } } class Dog extends Animal { public void newDog() { System.out.println("Dog 的新特性"); } public void shout() {
System.out.println("汪"); } } class Cat extends Animal { public void shout() { System.out.println("喵"); } } class Test { public void animalshout(Animal a) { a.shout(); } } public class PolyEx { public static void main(String[] args) { Animal d=new Dog();//(1) Dog d1= (Dog)d;//(3)父类对象强制转换成子类对象 d1.newDog(); //d.newDog(); d.shout(); Test t=new Test(); t.animalshout(d);//(2) t.animalshout(d1); } } 4 class ArrayEx{ public int[] subarray(int a[],int start,int end){ int subarr[] = new int[end-start]; for(int i=0,j=start;j
} return subarr; } } public class Test{ public static void main(String args[]){ ArrayEx arrex = new ArrayEx(); int arr[] = new int[10]; for(int i = 0;i
} class ShowBox{ void show(Box b){ System.out.println(b.length+" "+b.width+" "+b.height); } } class TestTwo{ public static void main(String args[]){ Box a = new Box(); a.set(3,4,5); ShowBox sbox = new ShowBox(); sbox.show(a); } } 6. class One{ int a = 5; void showB(){ int a = 3; int b = this.a; System.out.println("b = "+b); } }
public class ThisOne{ public static void main(String args[]){ One test = new One(); test.showB(); } } 7. class Mystatic{ private int x=3; public static void showx(){ System.out.println("x="+x); } public static int add(int m){ return m+x; } } class UseMystatic{ public static void main(String args[]){ Mystatic.showx(); System.out.println("add="+Mystatic.add(2)); } }
8. class Point { int x; int y; Point(){ x=0; y=0; //this(1,1); } Point(int a,int b){ x=a; y=b; } void show(){ System.out.println("x="+x+" y="+y); } } public class UsePoint { public static void main(String args[]){ Point p = new Point(); p.show(); } } 9. class Point{ private int x,y; Point(){ x=1; y=3; }
void showPoint(Point t){ System.out.println("x="+t.x+" } y="+t.y); void seeit(){ showPoint(this); } } public class UsePointThis { public static void main(String args[]){ Point p=new Point(); p.seeit(); } } 10 class Point{ static int x=2; int y=0; } public class UseStatic{ public static void main(String args[]){ System.out.println("利用类调用静态变量"); System.out.println("x="+Point.x); //System.out.println("y="+Point.y); Point p1=new Point(); System.out.println("利用对象调用"); System.out.println("x="+p1.x); System.out.println("y="+p1.y); Point p2=new Point(); p2.y=3; System.out.println("对象 p1 中 y 的值"+"y="+p1.y); System.out.println("对象 p2 中 y 的值"+"y="+p2.y); p1.x=6;
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