blocks|key|1614765|text|接口是面向对象编程中的一个概念，它支持多态性。基本上，接口就像一个契约，实现它的类同意提供某些功能，以便它们可以像使用该接口的其他类一样使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1614766|您的示例显示了保证它们具有可用的getPrice方法的类。然后，您可以编写利用具有此方法的对象的代码，而不必担心它是哪种类型的类。|1614767|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

An interface is a concept in Object Oriented programming that enables polymorphism. Basically an interface is like a contract, that by which classes that implement it agree to provide certain functionality so that they can be used the same way other classes that use the interface

Your example shows classes that guarantee that they have the getPrice method available. You can then write code that take advantage of objects that have this method without worrying about what kind of class it is.

blocks|key|1614829|text|接口允许您将接口与实现分开。当你想在你的代码中有正交性的时候，这是很方便的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1614830|基本上，您将能够创建接受Chargeable的函数，并且能够在其中传递任何对象，只要它实现了Chargeable。这允许您在需要更改Employee类时更加灵活。此外，它还允许您的方法接受任何“可收费”的对象。|offset|length|style|CODE|1614831|entityMap^0|0|C|A|1A|A|1U|8|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]|$D|N|E|O|F|G]|$D|P|E|Q|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|I|$]]

Interfaces allow you to separate the interface from implementation. This is handy when you want to have orthogonality in your code among other things.

Basically you will be able to create functions that accept a <code>Chargeable</code> and be able to pass any object in there as long as it implements <code>Chargeable</code>. This allows you to be flexible down the road if you need to change the <code>Employee</code> class. Also it allows your method to accept any object that is "chargeable".

blocks|key|1614872|text|在具有多重继承而不是接口的语言中，您有抽象类。在PHP中没有多重继承，所以你有接口。一个类可以实现各种接口。唯一的问题是保证你的类有一组特定的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1614873|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

In languages with multiple inheritance instead of interfaces you have abstract classes. In PHP there is no multiple inheritance, so you have interfaces. One class can implement various interfaces. The only point is to guarantee that your class has certain set of methods.

blocks|key|1400228|text|我正在努力摸索这一点(我想我正在读的是同一本书……)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1400229|在我看来，接口只是在实现接口的类上强制执行“契约”义务，以实现接口中出现的功能/属性。然而，实现接口的类/对象不是可以以一种独特的方式做到这一点，因为实现没有定义吗？|1400230|实际上并没有涉及到继承，不是吗？|1400231|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|$]]

I'm struggling to grok this myself at the moment (and I think I'm reading the same book as the OP...). 

It seems to me that interfaces simply enforce a "contractual" obligation on classes that implement the interface to implement functions/properties that appear in the interface. Yet, isn't it the case that classes/objects which implement the interface can do so in a unique fashion since the implementation is not defined? 

There is no actual inheritance involved is there?

blocks|key|1614979|text|让我给你举个例子来理解这类类的含义|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1614980|public+interface+transport{
public+double+getSpeed(){return(0/*the+speed*/);}
public+void+setSpeed(){return(0/*the+speed*/);}


}+++
class+car+extend+transport{
//implementation+of+transport+interface
public+double+getSpeed(){return(speed/*the+speed*/);}
public+void+setSpeed(){speed=250;}
}
class+train+extend+transport{
//implementation+of+transport+interface+
....

}

class+plane+extend+transport{
//implementation+of+transport+interface+
....
}|code-block|syntax|javascript|1614981|因此，接口类是一般的概念。|1614982|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

let me give you example to understand the the dimnation of this type of classes

<pre><code>public interface transport{
public double getSpeed(){return(0/*the speed*/);}
public void setSpeed(){return(0/*the speed*/);}


} 
class car extend transport{
//implementation of transport interface
public double getSpeed(){return(speed/*the speed*/);}
public void setSpeed(){speed=250;}
}
class train extend transport{
//implementation of transport interface 
....

}

class plane extend transport{
//implementation of transport interface 
....
}
</code></pre>

so the interface class is the general concept .

blocks|key|1615085|text|首先，接口结构为实现对外通信的类提供了接口。简单的例子就是电视机。电视是一个类，其上的按钮是接口。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1615086|使用接口的adv：|1615087|1-Java不支持多重继承。如果我们想从不同的类添加两个不同的方法，我们不能(扩展ClassA，ClassB)是不可能实现A，B没有问题的。|1615088|另一个adv是安全性和灵活性，可以给出一个更具体的例子，如果我们希望类的一些方法是不可访问的，我们如何做到这一点？多态性%2B接口我们可以这样做，如果我们不希望遍历和树皮方法应该是不可达的|1615089|abstract+class+Animal+{
++++String+name;
++++int+age;

++++public+Animal(String+name,+int+age)+{
++++++++super();
++++++++this.name+=+name;
++++++++this.age+=+age;
++++}

}

class+Dog+extends+Animal+implements+Run+{

++++public+Dog(String+name,+int+age)+{
++++++++super(name,+age);
++++++++//+TODO+Auto-generated+constructor+stub
++++}

++++@Override
++++public+void+run()+{
++++++++//+TODO+Auto-generated+method+stub

++++}

++++public+void+bark()+{

++++}

}

class+Cat+extends+Animal+implements+Climb+{

++++public+Cat(String+name,+int+age)+{
++++++++super(name,+age);

++++}

++++@Override
++++public+void+climb()+{
++++++++//+TODO+Auto-generated+method+stub

++++}

++++public+void+walk()+{

++++}

}

public+class+Main+{

++++public+static+void+main(String[]+args)+{

++++++++//+if+we+want+that+some+of+methods+of+the+class+are+not+reachable+how
++++++++//+can+we+do+that?
++++++++//+polymorphism+%2B+interface+we+can+do+that
++++++++//+for+example+if+we+do+not+want+walk+and+bark+methods+should+be
++++++++//+unreachable

++++++++Climb+cat+=+new+Cat("boncuk",+5);
++++++++Run+dog+=+new+Dog("karabas",+7);

++++++++//+see+we+cannot+reach+the+method+walk()+or+bark()
++++++++dog.walk();+//+will+give+an+error.+since+there+is+no+such+a+method+in+the+interface.

++++}

}}

++++enter+code+here|code-block|syntax|javascript|1615090|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|R|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|S|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Firstable, interfaces structures provide interface to classes implemented for communicating outside world. Easy example would be a television. Television is a class and buttons on it are interfaces. 

adv of using interfaces:

1-Java does not support multiple inheritance. If we want to add two different methods from different classes we cannot (extend ClassA,ClassB) is not possible implements A,B no problem.

2-The other adv is a security and flexibility An example can be given to be more specific
if we want that some of methods of the class are not reachable how can we do that?
polymorphism + interface we can do that 
if we do not want walk and bark methods should be unreachable

<pre><code>abstract class Animal {
 String name;
 int age;

 public Animal(String name, int age) {
 super();
 this.name = name;
 this.age = age;
 }

}

class Dog extends Animal implements Run {

 public Dog(String name, int age) {
 super(name, age);
 // TODO Auto-generated constructor stub
 }

 @Override
 public void run() {
 // TODO Auto-generated method stub

 }

 public void bark() {

 }

}

class Cat extends Animal implements Climb {

 public Cat(String name, int age) {
 super(name, age);

 }

 @Override
 public void climb() {
 // TODO Auto-generated method stub

 }

 public void walk() {

 }

}

public class Main {

 public static void main(String[] args) {

 // if we want that some of methods of the class are not reachable how
 // can we do that?
 // polymorphism + interface we can do that
 // for example if we do not want walk and bark methods should be
 // unreachable

 Climb cat = new Cat("boncuk", 5);
 Run dog = new Dog("karabas", 7);

 // see we cannot reach the method walk() or bark()
 dog.walk(); // will give an error. since there is no such a method in the interface.

 }

}}

 enter code here
</code></pre>

what is the purpose of interface when writing a class?

heres an example i've seen online.

<pre><code>&lt;?php
interface Chargeable {
 public function getPrice();
}

class Employee implements Chargeable {
 protected $price;

 public function getPrice() {
 return $this-&gt;price;
 }
}

$product = new Employee();

?&gt;
</code></pre>

purpose of interface in classes

Java

编写类时接口的用途是什么？这是我在网上看到的一个例子。<?phpinterface Chargeable { public function getPrice();}class Employee implements Chargeable { protected $price; public func...

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