blocks|key|1108940|text|你的意思是为什么我们需要接口，或者为什么我们不只使用抽象类？接口提供：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1108941|1)抽象和依赖倒置。高级类并不关心他们所使用的具体的低级类。你拥有的节制越多，你就会获得更多的灵活性。例如，您可以完全重写与DB一起工作的级别，并保持应用程序的其他级别不变，因为它们与接口一起工作，而不是与具体实现一起工作。|1108942|2)在Java中，接口提供多重继承|1108943|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Do you mean why do we need interfaces or why do we not using only abstract classes?
Interfaces provide:

1)Abstraction and dependency inversion. High-level classes don't care about concrete low-level class they work with. More abstration you have, more flexibility you get. For example, you can completely rewrite level that works with DB and you keep untouched other levels of your app because they work with interfaces but not with concrete implementation.

2)In Java interfaces provide multiple inheritance

blocks|key|1108832|text|你有没有检查过，关于Java接口的部分你有一个解释和一些Java示例|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1108833|http://www.javabeginner.com/learn-java/java-abstract-class-and-interface|1108834|示例1:下面是一个形状界面的示例|1108835|interface+Shape+{

++++public+double+area();
++++public+double+volume();
}|code-block|syntax|javascript|1108836|下面是一个实现Shape接口的Point类。|1108837|public+class+Point+implements+Shape+{

++++static+int+x,+y;
++++public+Point()+{
++++++++x+=+0;
++++++++y+=+0;
++++}
++++public+double+area()+{
++++++++return+0;
++++}
++++public+double+volume()+{
++++++++return+0;
++++}
++++public+static+void+print()+{
++++++++System.out.println("point:+"+%2B+x+%2B+","+%2B+y);
++++}
++++public+static+void+main(String+args[])+{
++++++++Point+p+=+new+Point();
++++++++p.print();
++++}
}|1108838|entityMap|0|LINK|mutability|MUTABLE|url^0|A|6|0|0|20|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|12|8|@]|D|@$9|13|A|14|1|15]]|E|$]]|$1|H|3|I|5|6|7|16|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|17|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|18|8|@]|D|@]|E|$]]|$1|Q|3|R|5|L|7|19|8|@]|D|@]|E|$M|N]]|$1|S|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|G]]]]

Did you check, the part with Java Interface you have an explanation and some Java example 

<a href="http://www.javabeginner.com/learn-java/java-abstract-class-and-interface" rel="nofollow">http://www.javabeginner.com/learn-java/java-abstract-class-and-interface</a>

Example 1: Below is an example of a Shape interface

<pre><code>interface Shape {

 public double area();
 public double volume();
}
</code></pre>

Below is a Point class that implements the Shape interface.

<pre><code>public class Point implements Shape {

 static int x, y;
 public Point() {
 x = 0;
 y = 0;
 }
 public double area() {
 return 0;
 }
 public double volume() {
 return 0;
 }
 public static void print() {
 System.out.println("point: " + x + "," + y);
 }
 public static void main(String args[]) {
 Point p = new Point();
 p.print();
 }
}
</code></pre>

blocks|key|1854142|text|您只是提供了interface要做的事情，以及它将如何完成，这将在实现中涵盖。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1854143|假设有一个接口驱动程序，您将声明一个方法drive()；|1854144|现在假设一个汽车司机实现了这个方法，然后他可以在那里编写他的代码。|1854145|如果飞行员实现了驱动方法，那么他的代码..|1854146|我希望天气晴朗。|1854147|entityMap^0|6|9|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|U|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|V|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|O|$]]

you are providing just the things to do by <code>interface</code> ,how it will get done that will be covered in implementation. 

Suppose there is an interface Driver you will declare a method drive(); 

now suppose a car driver implements this method then he can write his code there. 
If a pilot implements drive method then his code.. 

I hope its clear.

blocks|key|4593810|text|这是来自JavaRanch的Java+Beginner+FAQ部分的entry。这可能会有帮助。此外，请访问JavaRanch。特别是对于Java初学者来说，没有其他更好的替代品。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4593811|entityMap|0|LINK|mutability|MUTABLE|url|http://faq.javaranch.com/java/JavaBeginnersFaq|1|http://faq.javaranch.com/java/InterfaceVsAbstractClass|2|http://www.javaranch.com/^0|E|H|0|Y|5|1|1I|9|2|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]|$A|T|B|U|1|V]|$A|W|B|X|1|Y]]|C|$]]|$1|D|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]|N|$5|G|H|I|C|$J|O]]]]

Here is the <a href="http://faq.javaranch.com/java/InterfaceVsAbstractClass" rel="nofollow">entry</a> from JavaRanch's <a href="http://faq.javaranch.com/java/JavaBeginnersFaq" rel="nofollow">Java Beginner FAQ</a> section. It might be helpful.
Moreover, go to <a href="http://www.javaranch.com/" rel="nofollow">JavaRanch</a>. For Java beginners, particularly, there is no other better substitute.

blocks|key|3183216|text|接口用于描述两个对象的共同之处，但实现方式不同。我的书中给出的例子是鸭子。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3183217|假设你有两只鸭子|3183218|3183219|一个普通的活着的|unordered-list-item|3183220|和一个木头的|3183221|3183222|以及一个带有方法fly()的接口；|3183223|这两个都能飞。因此，Fly方法进入接口。因为当你实现一个接口时，你必然要实现该接口中的函数。(这就像是一份合同！)|3183224|所以Duck实现了IFly，在它的fly方法中，它所做的一切都是写给控制台:我可以飞。|3183225|而木头鸭子说“我不会飞”。|3183226|然后当你这样做的时候：|3183227|(C#，对不起，不知道java)|3183228|IFLy+duck+=+new+Duck()++++++duck.fly();+--+This+will+write+I+Can+fly.+++++Ifly+woodenduck+=+new+WoodenDuck()+woodenduck.fly()|offset|length|style|CODE|3183229|上面说我不能飞。|3183230|简而言之，接口描述了一个对象必须实现什么，这样你就可以把它看作是一个契约。|3183231|希望这能让它变得更清楚一些，一开始也遇到了很多麻烦。|3183232|(srry不能很好地解释)|3183233|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|3H|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1D|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|1F|8|@]|9|@]|A|$]]|$1|H|3|I|5|G|7|1G|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|1I|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1J|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1K|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1L|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1M|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1N|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1O|8|@$Y|1P|Z|1Q|10|11]]|9|@]|A|$]]|$1|12|3|13|5|6|7|1R|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|1S|8|@]|9|@]|A|$]]|$1|16|3|17|5|6|7|1T|8|@]|9|@]|A|$]]|$1|18|3|19|5|6|7|1U|8|@]|9|@]|A|$]]|$1|1A|3|-4|5|6|7|1V|8|@]|9|@]|A|$]]]|1B|$]]

A interface is used to describe what 2 objects have in common but implement differntly. 
The example given by mybook was with ducks.

Suppose u have 2 ducks

<ul>
<li>A normal alive one</li>
<li>and a wooden one</li>
</ul>

And an interface Ifly with the method fly();

Both are able to fly. So the Fly method goes in the interface. Because when u implement an interface, U're bound to implement the functions in that interface. (it's like a contract!)

so Duck implements IFly and in its fly method all it does write to the console saying: I Can fly.

While the wooden duck one says "I Can't fly".

then when u do this:

(C# sorry don't know java)

<code>IFLy duck = new Duck() 
 duck.fly(); -- This will write I Can fly.
 Ifly woodenduck = new WoodenDuck()
woodenduck.fly()</code>

that says I Can't fly.

In short, A interface describes what an object HAS to implement so u could see it as an contract.

Hope this makes it a bit clearer, had a lot of trouble with this in the beginning too.

(srry can't explain really good)

blocks|key|4593929|text|+(在java中)是一个不可实例化的抽象类(它没有构造函数)，它提供了公共方法，所有继承这些方法的子类都必须实现这些方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|4593930|此外，继承的一个优点是便于使用multiple+inheritance。|4593931|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Multiple_inheritance^0|C|6|Z|2|1F|3|0|F|K|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|W|8|@]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|H|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

An <a href="http://en.wikipedia.org/wiki/Interface_%28Java%29" rel="nofollow">interface</a> (in java) is an uninstatiable abstract class (it has no constructors) that provides public methods that all subclasses that inherits them must implement.

Also, one advantage of having inheritance is to facilitate with <a href="http://en.wikipedia.org/wiki/Multiple_inheritance" rel="nofollow">multiple inheritance</a>.

blocks|key|1111523|text|老实说，你应该花点时间读一读关于Java的好书。我推荐赫伯特·舒尔特的Java+Complete+Reference。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1111524|首先理解以下术语及其在OO上下文中的意义：|1111525|1111526|Implementation|unordered-list-item|1111527|
|1111528|Polymorphism|1111529|
发布的|1111530|类型|ordered-list-item|1111531|合同|1111532|1111533|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@]|9|@]|A|$]]|$1|D|3|5|5|6|7|X|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|Y|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|Z|8|@]|9|@]|A|$]]|$1|J|3|K|5|G|7|10|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|11|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|P|7|13|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|U|$]]

Honestly , you should invest time in reading good book on Java. I recommend The Java Complete Reference by Herbert Schildt. 

Start by understanding the following terms and their significance in OO context :

<ol>
<li>Type </li>
<li>Contract published by a type</li>
<li>Implementation</li>
<li>Polymorphism</li>
</ol>

Please explain using plain english why we need and why we use Interface in Object Oriented development.

I am in serious confusion.

[+] I'm working on Java. Please provide sample code in Java if any.

Thanks all.

Interface in plain english

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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请用通俗易懂的英语解释为什么我们需要和为什么我们在面向对象的开发中使用接口。我陷入了严重的困惑。+我正在研究Java。如果有的话，请用Java提供示例代码。谢谢大家。

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