1.Shap
package com.yfs.javase;
public class Shape /*extends Object */{ //默认继承object object方法全部继承
//计算面积方法
public double getArea() {//代码完全没用
System.out.println("计算面积");
return 0;
}
}
2.Circle
package com.yfs.javase;
public class Circle extends Shape {
private double r;
public Circle(double r) {
this.r = r;
System.out.println("创建圆形面积");
}
// public double getArea() {//覆盖父类的方法
// System.out.println("计算圆形面积...");
// return 3.14 * r * r;
// }
}
3.Triangle
package com.yfs.javase;
public class Triangle extends Shape {
private double height;
private double width;
public Triangle(double height, double width) {
this.height = height;
this.width = width;
System.out.println("创建三角形面积");
}
public double getArea() {
System.out.println("计算三角形面积...");
return 1.0 / 2 * width * height;
}
}
4.Rectangle
package com.yfs.javase;
public class Rectangle extends Shape {
private double width;
private double length;
public Rectangle(double width, double length) {
this.width = width;
this.length = length;
System.out.println("创建矩形面积");
}
public double getArea() {
System.out.println("计算矩形面积...");
return width * length;
}
}
5.shap测试
package com.yfs.javase;
public class ShapeTest {
public static void main(String[] args) {
Shape[] shapes = new Shape[10];
Shape s = new Shape();//创建这个类对象
s.getArea();
}
}
6.抽象类
package com.yfs.javase;
//类中有抽象方法 类必须是抽象的
public abstract class Demo1 { public abstract void method(); //没有方法体 抽象方法
public abstract double method1(int a, String name);
public abstract double method1(String name,int a);
//抽象类可以声明普通方法 子类可以继承
public void method2() {
System.out.println("call method2()... ");
}
//普通方法是否可调用抽象方法
public void method3() {
method();//不会调用父类的方法 调用子类对象的方法 多态
}
}
abstract class Child extends Demo1 {
@Override
public void method() {
System.out.println("call () .......");
}
}
class Son extends Child { @Override
public double method1(int a, String name) {
// TODO Auto-generated method stub
return 0;
} @Override
public double method1(String name, int a) {
// TODO Auto-generated method stub
return 0;
} } class Children extends Demo1 {
//子类继承抽象类 必须覆盖抽象方法
@Override
public void method() {
System.out.println("子类覆盖的抽象方法..."); } @Override
public double method1(int a, String name) {
System.out.println("name = " + name);
System.out.println("a = " + a);
return 0;
} @Override
public double method1(String name, int a) {
// TODO Auto-generated method stub
return 0;
} public static Demo1 test (Demo1 d) { return new Children();
} }
7.抽象类测试
package com.yfs.javase;
public class Demo1Test {
/**
* 1.抽象类不能实例化
* 2.子类必须覆盖抽象类的抽象方法
*/
public static void main(String[] args) {
Demo1 d1;//声明引用
//创建对象
//d1 = new Demo1();//抽象类不能实例化
d1 = new Children();
d1.method();
d1.method2();
Children c1 = new Children();
c1.method2();
System.out.println("============================");
d1.method3();
c1.method3();
d1.method1(15, "影分身");
Demo1 d2 = Children.test(c1);
Demo1 c2 = Children.test(d1);
d2.method2();
c2.method2();
}
}