面向对象3

package LESSON6;

public class DEMO2 {
    int a;//实例变量
    static int b;//类变量
    //普通代码块：{}，每次创建对象之前都会执行。可以初始化类变量和实例变量
    {
        a=1;
        b=2;
        
        System.out.println("普通代码块");
    }
    //静态代码块：static{}，类加载之后先执行，且只会执行一次。只能初始化类变量。
    static{
        //a=3;报错
        b=4;
        System.out.println("静态代码块");
    }
    public DEMO2(){
        System.out.println("无参构造器");
    }
    public void test(){
        System.out.println("test方法");
    }

    
    public static void main(String[] args) {
        //执行顺序：静态代码块>>普通代码块>>构造器>>对象调用的属性以及方法
        DEMO2 demo=new DEMO2();
        DEMO2 demo2=new DEMO2();
        demo.test();

    }

}

package LESSON6;

public class DEMO1 {
    public static String name;
    public int age;
    public static void eat(){
        //静态方法里只能使用静态的变量
//        public static int eat;//

        System.out.println("吃");
    }
    public void drink() {
        System.out.println("喝");
        
    }
    public static void main(String[] args) {
        DEMO1.name="张三";
        System.out.println(name);
        DEMO1 de1=new DEMO1();
        DEMO1 de2=new DEMO1();
        de1.name="李四";
        System.out.println(name);
        de2.name="jack";
        de1.age=20;
        System.out.println(name);
        System.out.println(de1.age);
        
        DEMO1.eat();
        de1.eat();
        de1.drink();

    }

}

package LESSON6;
class user{
    public String username;
    private String password;//private,封装，私有化。只能在本类访问
    public String getPassword(){//获取私有属性的值
        return password;        
    }
    public void setPassword(String password){//修改私有属性的值
        this.password=password;
        
    }
}

public class DEMO3 {        
    public static void main(String[] args) {
        user demo=new user();
        demo.setPassword("123456");
        System.out.println(demo.getPassword());

    }

}

package LESSON6;

class Person{
    public Person(String name,int i){
        this.name=name;
        System.out.println("父类有参构造器");
    }
    public String type="不分男女";
    public String name;
    private int age;
    public void eat(){
        System.out.println("吃面");
    }
}
class Work extends Person{
    public Work(){
        super("",1);//调用父类构造器,必须要在子类构造器中调用
        System.out.println("子类无参构造器");
        
    }
    public String type="男";
    public String name="jack";
    public int id;
    public void work(){
        System.out.println("我在工作");
        System.out.println(super.type);//调用父类属性
    }
    
    //重写(override)与父类相同的方法
    public void eat(){
        System.out.println("我只喜欢吃排骨");    
        super.eat();//调用父类方法
    }
    
    
    
}

public class DEMO4 {
    
    public static void main(String[] args) {
        Person person=new Person("rose",1);
        person.eat();
        System.out.println(person.name);
        System.out.println("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\");
        
        Work work=new Work();    
        work.id=123456;
        work.eat();
        work.work();
        System.out.println(work.id+"\t"+work.name);
    }

}