{Java Detail} Interface and Abstract Class

关于接口，一个一直不确定的问题就是它到底能不能拥有字段，下面的代码回答：可以。

 

由此引出有意思的一点是，java 中，接口的字段居然是默认的会以 public final static 修饰，何以如此？见代码注释。

 

• 其实最精髓的就是把握Java中接口的设计原则：它更像一种契约，白纸黑字，无可更改。
• 至于抽象类，它和普通类的唯一本质区别，在我看来，就是它可以包含无方法体的抽象方法，而由此，也导致它不能直接实例化。
• 至于两者的区别，上面谈到的字段算一个，其实最本质的我感觉还是设计理念不同，一个很好的说法是 接口 是用来代表Can Do 的,而 抽象类 则是 is a.    超人和鸭子都Can fly,但两者显然非同一物种。所以好的做法是 两者都实现Fly 接口，而鸭子，还是和鸡啊鹅啊什么的去一起继承自 禽 这一抽象类吧。

 

 

• 接口

/** 
* 1.can interface have fields? yes,but it is [public final and static] by 
* default. 
* 
* Interface is like an contract,class who have used it must follow it. so it is 
* important that the contract is quite stable(or immutable), 
* 
* so the fields is final(can not be changed) and static(every one 
* has the same copy of it,no one is different). 
* 
* while,it is also public(if it is private,what does it used for? It is 
* useless). 
* 
* @author mmLiu 
* 
*/ 
public interface myInterface { 
public final static int filed1 = 1; 
} 

 

•  抽象类

/**
 * I think the only essential difference between abstract class and normal class
 * is that the abstract one can have unimplemented method(so called abstract
 * method).
 * <p>
 * and As a result,it can not be initialized.
 * 
 * @author mmLiu
 * 
 */
public abstract class myAbstractClass {
	int myInt;

	/**
	 * Constructor
	 */
	public myAbstractClass() {
		System.out.println("Parent's Constructor");
	}

	/**
	 * Abstract method does not have method body(otherwise how can it be called
	 * abstract?).
	 * <p>
	 * while ,an abstract class does not have to have an abstract method.you can
	 * safely remove this method,it is still right.
	 * 
	 * @param a
	 * @return
	 */
	public abstract int myVirtualMethod(int a);

	public int myMethod2(int a) {
		return a;
	}
}

 

 

 

ps.关于这种文章主体存在于代码中的写作方式，我承认是因为我懒，我自己都很怀疑这样的文章，除对我存在可读性外，是否还能有他人，但考虑到我的博客会不会真的居然还会有读者，所以，让我懒下去吧。