1.Java的继承，关键词Extends

1 package cn.mwf.oo; 2  3 public class TextExtends { 4     public static void main(String[] args) { 5         Student s = new Student("侠客小飞", 60, "计算机科学与技术"); 6         s.rest(); 7         s.study(); 8     } 9 10 }11 class Person{12     String name;13     int height;14     public void rest() {15         System.out.println("休息一会！");16     }17 }18 class Student extends Person{19     String major;//专业20     public void study() {21         System.out.println("在图书管学习java！");22     }23     public Student(String name,int height,String major) {24         this.name = name;25         this.height = height;26         this.major = major;27     }28 }

2.方法的重写

1 package cn.mwf.oo; 2 //方法的重写 3 public class TestOverride { 4     public static void main(String[] args) { 5         Vehicle v1 = new Vehicle(); 6         v1.run(); 7         v1.stop(); 8         Vehicle v2 = new Hourse(); 9         v2.run();10         v2.stop();11         Vehicle v3 = new Airplane();12         v3.run();13         v3.stop();14     }15 }16 //Vehicle类17 class Vehicle{18     public void run() {19         System.out.println("跑···");20     }21     public void stop() {22         System.out.println("停止···");23     }24 }25 //Hourse类继承Vehicle类26 class Hourse extends Vehicle{27     public void run() {28         System.out.println("嘚嘚嘚的跑");29     }30 }31 //Airplane类继承Vehicle类32 class Airplane extends Vehicle{33     public void run() {34         System.out.println("在空中飞");35     }36     public void stop() {37         System.out.println("在空中不能停，会掉下来");38     }39 }

3.重写toString方法

1 package cn.mwf.oo; 2  3 public class TestObject { 4     public static void main(String[] args) { 5         TestObject to = new TestObject(); 6         System.out.println(to.toString()); 7          8         Person2 p2 = new Person2("茜茜",6); 9         System.out.println(p2.toString());10     }11     public String toString() {12         return "测试Object对象";13     }14 }15 class Person2{16     String name;17     int age;18     19     public String toString() {20         return name+",年龄:"+age;21     }22     public Person2(String name, int age) {23         this.name = name;24         this.age = age;25     }26 }