java继承简例

面向对象程序设计 封装 继承多态 在类的声明中，需要定义类的名称，对该类的访问权限和该类的其他类的关系类的声明格式如下：   【修饰符】class  类名【extends 父类名】implements 接口列表{}修饰符：public  private abstract   final  把类装进包里，在开头声明包的名字即可 package com.wgh public  class Cric{  final float PI =3.1415f; public void draw(){     System.out.println(“this is a test programming!”)}}继承：public  class Animal{   public Boolean live =true;  public  String skin =” “;  pubic  void eat(){   System.out.println(“he can eat ！”);}  public void move (){  System.out.println(“he can move”);}}public  class  Brid extends Aminal{ public String skin=”羽毛”;public void move(){    System.out.println(“he can fly”);  //覆盖了父类的成员方法}}Java中用接口来解决多重继承的问题1.定义了两个接口package goodjob;public interface Caulate {    final float PI = 3.14159f;    float getArea(float r);    float getCircu(float r);    void draw();}package goodjob;public interface GeometryShape {   final float PI = 3.1415926f;   float getArea(float r);   float getCircu(float r);   void draw();}2 然后在类中继承两个接口，逗号隔开：  public class Test  implements Caulate,GeometryShape /** *  */package goodjob;/** * @author Mr.Lv * */public class Test  implements Caulate,GeometryShape{        public float getArea(float r){            float area = Caulate.PI*r*r;            return area;            }        public float getCircu(float r){            float Cir = 2*Caulate.PI*r;            return Cir;        }        public void draw(){            System.out.println("画一个同心圆！");        }    /**     * @param args     */    public static void main(String[] args) {        // TODO Auto-generated method stub      Test test = new Test();  // Test test;      float r = 7;      float  area=test.getArea(r);      float  Cir=test.getCircu(r);      System.out.println("圆的面积为:"+area);      System.out.println("圆的周长为:"+Cir);      System.out.println("圆的面积为:"+test.getArea(8));      test.draw();    }}Console:圆的面积为:153.93791圆的周长为:43.98226圆的面积为:201.06177画一个同心圆！集合  Colllection  List:  ArrayList   LinkedListSet:   HashSet     TreeSetMap: HashMap  捕捉异常：printStackTrace():方法输出异常的详细描述信息  try{代码块1；}catch(Exception e){      e.printStackTrace();    }线程：开启：start()\挂起： sleep()/join()/wait()_