抽象类&&接口做形参（其实同理）

• 抽象类：传入该抽象类的子类对象

eg：

package javaBasic;

public class TestAbstract {
	public static void main(String[] args) {
		 FreshLad fl = new FreshLad();//想调ta的方法，要先new出来ta先呀~
		 Lad l = new Fool();//间接实现抽象类
		 fl.method(l);
	}
}

abstract class Lad{
	public abstract void need();
}

class FreshLad{
	public void method(Lad l) {
		l.need();
	}
}

class Fool extends Lad{
	public void need() {
		System.out.println("memorize more words\ncet-6 come on!");
	}
}

• 接口：传入该接口的实现类对象
  eg如下：

  package javaBasic;
  
  public class TestAbstract {
  	public static void main(String[] args) {
  		 /*FreshLad fl = new FreshLad();
  		 Lad l = new Fool();//间接实现抽象类
  		 fl.method(l);*/
  		FreshYouth fy = new FreshYouth();
  		Youth y = new Idiot();
  		fy.method(y);
  	}
  }
  
  interface Youth{
  	abstract void struggle();
  }
  
  class FreshYouth{
  	public void method(Youth y) {
  		y.struggle();
  	}
  }
  
  class Idiot implements Youth{
  	public void struggle() {
  		System.out.println("study grammer well\ncet-6 fighting!!");
  	}
  }