11.13 this 关键字

1.this关键字

package cn.dede.w;
class A
{
    private B b=null;
    public void fun()
    {
        this.b=new B(this);//当前值赋值给b
        this.b.fun();//到23
    }
    public void print()
    {
        System.out.println("hi xn");
    }
}

class B
{
    private A a=null;
    public B(A a)
    {
        this.a=a;
    }
    public void fun()
    {
        this.a.print();//到18
    }
}

public class ClassAB
{
    public static void main(String args[])
    {
        new A().fun();//到第2行
    }
}

2. 父类初级

package cn.dede.w;
abstract class A1
{
    public abstract void fun();
}
class B1 extends A1
{
    public void fun()
    {
        System.out.println("hi xn");
    }
}
public class FirstAbstract 
{
    public static void main(String agrs[])
    {
        B1 b=new B1();//
        b.fun();
    }
}

3.父类中级

package cn.dede.w;
abstract class A2
{
    private String name;
    public A2(String name)
    {
        this.name=name;
    }
    public String getName()
    {
        return this.name;
    }
    public abstract void fun();
}

class B2 extends A2{
    public B2(String name)
    {
        super(name);
    }
    public void fun()
    {
        System.out.println(super.getName());
    }
}
public class AbstractDemo1 
{
    public static void main(String args[])
    {
        B2 b=new B2("xn" );
        b.fun();
    }
}

4.

package cn.dede.w;
public abstract class PersonA1
{
    private String name;
    private int age;
    private String songs;
    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;
    }
    public String getSongs()
    {
        return songs;
    }
    public void setSongs(String songs)
    {
        this.songs=songs;
    }
    public PersonA1(String name,int age, String songs)
    {
        this.name=name;
        this.age=age;
        this.songs=songs;
    }
    public PersonA1()
    {
        super();//作为一个特殊的关键字super表示调用父类的构造函数；它有动态类型，就是当前这个对象的类型。你可以对它调用成员函数，把它传递给别的函数，等等等等，静态地选择父类的那个版本。
    }
    public String toString()
    {
        return "Person[name="+ name +",age="+ age +",songs="+ songs +"]";
    }
    public abstract String speak();
}

package cn.dede.w;
public class PersonStudent extends PersonA1
{
    private float score;

    public PersonStudent(String name,int age,String songs,float score)
    {
        super(name,age,songs);
        this.setScore(score);
    }
    public String speak() 
    {    
        return "身份标签-》学生; 我叫："+super.getName()+" "+super.getAge()+"岁"+super.getSongs()+" "+this.score+"分";
    }
    public float getScore()
    {
        return score;
    }
    public void setScore(float score)
    {
        this.score=score;
    }
}

package cn.dede.w;
public class PersonWorker extends PersonA1
{
    private float salary;
    
    public PersonWorker(String name,int age,String songs,float salary)
    {
        super(name,age,songs);
        this.setSalary(salary);
    }
    public float getSalary()
    {
        return salary;
    }
    public void setSalary(float salary)
    {
        this.salary=salary;
    }
    public String speak()
    {
        return"工人说 -->我叫："+super.getName()+" "+super.getAge()+"岁 "+super.getSongs()+"  "+this.salary+"元" ;
    }
    
}

package cn.dede.w;
public class AbstractDemo2 
{
    public static void main(String[]args)
    {
        PersonA1 student=new PersonStudent("仙女",13,"崂山道士",99f);
        PersonA1 worker=new PersonWorker("刘全有",33,"崂山道士",9999f);
        print(student.speak());
        print(worker.speak());
    }
    private static void print(String speak)
    {
        System.out.println(speak);
    }
}

 5.

抽象类练习

package cn.dede.w;
abstract class A3
{
    public abstract void fun();
}
class B3 extends A3
{
    public void fun()
    {
        System.out.println("yeah");
    }
}
public class AbstractDemo3 
{
    public static void main(String args[])
    {
        A3 a=new B3();
        a.fun();
    }
}