20120709-the key factor affecting explicit or implicit interface implementation

本文详细探讨了在面向对象编程中,如何通过实现接口来扩展类的功能,包括接口的隐式实现、显式实现以及一个类同时实现多个接口的情况。通过实例展示了不同情况下的接口使用与类的行为差异。



1. first situation:

    one class implement one interface

   and all the interface implementation is implicit

   

 public interface IBankAccount
  {
    void PayIn(decimal amount);
    bool Withdraw(decimal amount);

    decimal Balance{get;}

  }


 

public class SaverAccount : IBankAccount
  {
    //类SaverAccount独有的
    public void PayIn2()
    {

    }

    //接口IBankAccount可以访问的
    public void PayIn(decimal amount)
    {

    }
    //接口IBankAccount可以访问的
    public bool Withdraw(decimal amount)
    {
      return false;
    }
    //接口IBankAccount可以访问的
    public decimal Balance
    {
      get
      {
        return 1;
      }
    }
  }


when use IBankAccount

  IBankAccount ba = new SaverAccount();
      ba.PayIn(1);
      SaverAccount sa = new SaverAccount();
      sa.PayIn(2);
      sa.PayIn2();//接口不能调用


 

2. the second situation

 

 

//the tiny difference is PayIn is explicit implementation
   //接口IBankAccount可以访问的
    public void IBankAccount.PayIn(decimal amount)
    {

    }

 

 //此时PayIn不可调用
      sa.PayIn(2);

3. one class implement multiple interface

each interface can only invoke the member and function that is assigned by itself.

if the class explicit one interface's function, the instance of this class couldn't invoke the explicit interface fuction

 

 

 

 

 

 

 

    
### Reasons for Avoiding Implementation Types and Using Interfaces #### 1. Code Flexibility Using interfaces allows the code to be more flexible. If a method is written to accept an `ArrayList`, it can only work with `ArrayList` objects. However, if it accepts a more general interface like `List`, it can work with any class that implements the `List` interface, such as `LinkedList` or `Vector`. This means that the underlying implementation can be easily changed without modifying the calling code. For example, if the performance requirements change and a `LinkedList` is more suitable than an `ArrayList`, the change can be made without affecting the code that uses the list. #### 2. Loose Coupling Interfaces promote loose coupling between different parts of the code. When classes depend on interfaces rather than specific implementations, the classes are less tightly bound to each other. This makes the code easier to maintain and test. For instance, in unit testing, mock objects that implement the interface can be used instead of real implementations, which simplifies the testing process. #### 3. Polymorphism Interfaces enable polymorphism, which is a fundamental concept in object - oriented programming. Polymorphism allows objects of different classes that implement the same interface to be treated uniformly. This can lead to more concise and reusable code. For example, a method can accept a collection of objects that implement an `Iterable` interface and perform operations on them regardless of their specific implementation. ### Methods to Avoid Using Implementation Types and Use Interfaces #### 1. Method Parameter Declaration When defining methods, use interfaces as parameter types instead of specific implementation types. For example: ```java import java.util.List; import java.util.ArrayList; public class InterfaceExample { public static void printList(List<String> list) { for (String element : list) { System.out.println(element); } } public static void main(String[] args) { List<String> myList = new ArrayList<>(); myList.add("Hello"); myList.add("World"); printList(myList); } } ``` In this example, the `printList` method accepts a `List` interface, so it can work with any class that implements the `List` interface. #### 2. Variable Declaration Declare variables using interfaces rather than specific implementation types. For example: ```java import java.util.List; import java.util.ArrayList; public class VariableDeclarationExample { public static void main(String[] args) { // Use interface type for variable declaration List<String> myList = new ArrayList<>(); myList.add("Java"); myList.add("Programming"); } } ``` Here, the variable `myList` is declared as a `List`, which allows it to be assigned any object of a class that implements the `List` interface. #### 3. Return Types When a method returns a collection or an object, use an interface as the return type. For example: ```java import java.util.List; import java.util.ArrayList; public class ReturnTypeExample { public static List<String> getList() { List<String> list = new ArrayList<>(); list.add("Element 1"); list.add("Element 2"); return list; } public static void main(String[] args) { List<String> result = getList(); } } ``` The `getList` method returns a `List` interface, so the calling code does not depend on the specific implementation of the list.
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