多態

package day8;

public abstract class Instrument {
    public abstract void play();
}

package day8;

public class Piano extends Instrument{

    @Override
    public void play() {
        // TODO Auto-generated method stub
        System.out.println("yueguangqu");
    }
}

package day8;

public
 
 class Violin extends Instrument{
    
    public void play() {
        // TODO Auto-generated method stub
        System.out.println("風吹麥浪");
    }
}

package day8;

//多態類題型：
//使用繼承
//子類重寫父類的方法
//父類引用子類對象

public class Artist {
//    public void make(Piano piano){
//        piano.play();
//    }
//    public void make(Violin violin){
 
//        violin.play();
//    }
    
    public void make(Instrument instrument){
        instrument.play();
    }
}

package day8;

public class Test {
    public static void main(String[] args) {
        Artist artist = new Artist();
        Piano piano = new Piano();
        artist.make(piano);
        Violin violin 
 
= new Violin();
        artist.make(violin);
    }
}

================================================================================================================

接口

package day83;

public interface InterfaceDemo {
    //1:接口不能被實例化
    //2：接口裏的方法默認都是public類型的抽象方法
    //所有public abstract修飾可以忽略
    //3:類是單繼承，但是類可以實現多個接口
    //4:在接口裏定義的屬性都是public類型的靜態常量
    //public static final都是可以省略的
    //5:接口可以繼承多個接口，可以得到父級接口裏所有的屬性和方法
    
    public abstract void showName();
    
    public static final int AGE = 10;
}

package day83;

public interface InterfaceDemo2 {
    void showName2(); 
}

package day83;

public abstract class Father {
    public abstract void showFatherName();
}

package day83;

public abstract class Father2 {
    public abstract void showFatherName2();
}

package day83;

public interface ChildInterface extends InterfaceDemo,InterfaceDemo2{

}

package day83;

import java.nio.channels.ShutdownChannelGroupException;

public class Test extends Father implements InterfaceDemo,InterfaceDemo2{
    public static void main(String[] args) {
//        Interface demo = new InterfaceDemo();是不可以的
        Test test = new Test();
        
    }
    @Override
    public void showName() {
        // TODO Auto-generated method stub
        
    }
    @Override
    public void showName2() {
        // TODO Auto-generated method stub
        
    }
    @Override
    public void showFatherName() {
        // TODO Auto-generated method stub
        
    }
}

=======================================================================================================

綜合類

package day86;

public class A4Paper implements Paper{

    @Override
    public void pageSize() {
        System.out.println("使用A4紙！");
    }

}

package day86;

public class B5Paper implements Paper{
    @Override
    public void pageSize() {
        System.out.println("使用B5紙！");
    }
}

package day86;

public class BlackInk implements Ink{

    @Override
    public void inkColor() {
        System.out.println("使用黑白墨！");
    }

}

package day86;

public class ColorInk implements Ink{

    @Override
    public void inkColor() {
        System.out.println("使用彩墨！");
    }

}

package day86;

public interface Ink {
    void inkColor();
}

package day86;

public interface Paper {
    void pageSize();
}

package day86;

public class Printer {
    public Ink ink;
    public Paper paper;
    public void print(String content){
        ink.inkColor();
        paper.pageSize();
        System.out.println(content);
    }
    public static void main(String[] args) {
        Printer printer = new Printer();
        printer.ink = new BlackInk();
        printer.paper = new A4Paper();
        printer.print("我是打印內容！");
        
    }
    
}

java之day8多態