目录

• 继承概述、使用继承的好处
• • 总结
• 继承的设计规范、内存运行原理
• • 总结
• 继承的特点
• • 总结
• 继承后：成员变量、成员方法的访问特点
• • 总结
• 继承后：方法重写
• 继承后：子类构造器的特点
• • 总结
• 继承后：子类构造器访问父类有参构造器
• • 总结
• this、super使用总结

继承概述、使用继承的好处

package com.zixin.d5_extends;public class People {public void run(){System.out.println("人会跑~~");}}

package com.zixin.d5_extends;public class Student extends People{}

package com.zixin.d5_extends;public class Test {public static void main(String[] args) {Student s =new Student();s.run();}
}

总结

1．什么是继承?继承的好处是啥?

• 继承就是java允许我们用extends关键字，让一个类和另一个类建立起一种父子关系。
• 提高代码复用性，减少代码冗余，增强类的功能扩展性。

2．继承的格式

• 子类 extends 父类

3．继承后子类的特点?

• 子类继承父类，子类可以得到父类的属性和行为，子类可以使用。Java中子类更强大

继承的设计规范、内存运行原理

package com.zixin.d6_extends_test;public class People {private String name;private int age;public void queryCourse(){System.out.println(name + "再查看课表~~");}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

package com.zixin.d6_extends_test;public class Student extends People {public void writeInfo(){System.out.println(getName()+"写下了：学习语法，好开心~~");}
}

package com.zixin.d6_extends_test;public class Test {public static void main(String[] args) {Student s =new Student();s.setName("嘻哈");s.setAge(999);System.out.println(s.getName());System.out.println(s.getAge());s.queryCourse();s.writeInfo();}
}

总结

1．继承需要满足什么样的设计规范?

• 子类们相同特征（共性属性，共性方法）放在父类中定义。
• 子类独有的的属性和行为应该定义在子类自己里面。

继承的特点

package com.zixin.d7_extends_feature;public class Test {public static void main(String[] args) {Tiger t = new Tiger();
//        t.eat();}
}class  Animal{private void eat(){System.out.println("动物要吃东西~");}
}class Tiger extends Animal{}

package com.zixin.d7_extends_feature;public class Test {public static void main(String[] args) {Tiger t = new Tiger();
//        t.eat();System.out.println(Tiger.location);}
}class  Animal{private void eat(){System.out.println("动物要吃东西~");}public static String location = "长隆动物园";
}class Tiger extends Animal{}

总结

1．继承有哪些特点?
子类可以继承父类的属性和行为，但是子类不能继承父类的构造器。
Java是单继承模式:一个类只能继承一个直接父类。
Java不支持多继承、但是支持多层继承。
Java中所有的类都是Object类的子类。

继承后：成员变量、成员方法的访问特点

package com.zixin;public class d8_extends_field_method {public static void main(String[] args) {Dog d =new Dog();d.run();d.lookDoor();d.showName();}
}class Animal{public String name = "动物名";public void run(){System.out.println("动物可以跑~");}
}class Dog extends Animal{public String name="狗名";public void lookDoor(){System.out.println("狗可以看门");}public void showName(){
//        String name ="局部名";System.out.println(name);System.out.println(this.name);System.out.println(super.name);super.run();run();}public void run(){System.out.println("狗跑的贼快~");}
}

总结

继承后：方法重写

package com.zixin.d9_extends_override;public class Test {public static void main(String[] args) {NewPhone iphone = new NewPhone();iphone.call();iphone.sendMsg();}
}class NewPhone extends Phone{@Overridepublic void call(){super.call();System.out.println("开始视频童话");}@Overridepublic void sendMsg(){super.sendMsg();System.out.println("发送有趣的图片~");}
}
class Phone{public void call(){System.out.println("打电话~");}public void sendMsg(){System.out.println("发短信~");}
}

继承后：子类构造器的特点

package com.zixin.d10_extends_constructor;public class Animal {public Animal(){System.out.println("父类Animal无参构造器被执行");}
}

package com.zixin.d10_extends_constructor;public class Dog {public Dog(){System.out.println("子类Dog无参数构造器被执行~");}public Dog(String name){System.out.println("子类Dog有参数构造器被执行");}
}

package com.zixin.d10_extends_constructor;public class Test {public static void main(String[] args) {Dog d1 = new Dog();System.out.println(d1);System.out.println("-------");Dog d2 = new Dog("土狗");System.out.println(d2);}}

总结

1．子类继承父类后构造器的特点是什么样的?
子类中所有的构造器默认都会先访问父类中无参的构造器，再执行自己。

继承后：子类构造器访问父类有参构造器

package com.zixin.d11_extends_constructor;public class People {private String name;private int age;public People() {}public People(String name, int age) {this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

package com.zixin.d11_extends_constructor;public class Teacher extends People{public Teacher(){}public Teacher(String name , int age){super(name,age);}
}

package com.zixin.d11_extends_constructor;public class Test {public static void main(String[] args) {Teacher t = new Teacher("王阳明",14);System.out.println(t.getAge());System.out.println(t.getName());}
}

总结

1、super调用父类构造器的作用是什么?
通过调用父类有参数构造器来初始化继承自父类的数据

this、super使用总结

package com.zixin.d12_this;public class Student {private String name;private String schoolName;public Student(){}public Student(String name){this(name,"之见者");}public Student(String name, String schoolName) {this.name = name;this.schoolName = schoolName;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSchoolName() {return schoolName;}public void setSchoolName(String schoolName) {this.schoolName = schoolName;}
}

package com.zixin.d12_this;public class Test {public static void main(String[] args) {Student s1 =new Student("许青","七血瞳");System.out.println(s1.getName());System.out.println(s1.getSchoolName());Student s2 = new Student("张三丰");System.out.println(s2.getName());System.out.println(s2.getSchoolName());}}