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Why should the interface for a Java class be preferred?

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陌清茗
陌清茗 2020-11-22 05:43

PMD would report a violation for:

ArrayList list = new ArrayList();



The violation was \"Avoid using implementat         


        
      
      
      

        

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                 忘掉有多难 
              
              
    
                
                   忘掉有多难
                                             
                
                
                (楼主)
            
              
                  
    
                2020-11-22 06:18
              
    

            
    
            
    
              
              

    
  
    Why should the latter with List be used instead of ArrayList?
    

    


    It's a good practice : Program to interface rather than implementation
    


    By replacing ArrayList with List, you can change List implementation in future as below depending on your business use case.
    


    List list = new  LinkedList(); 
/* Doubly-linked list implementation of the List and Deque interfaces. 
 Implements all optional list operations, and permits all elements (including null).*/



    OR
    


    List list = new  CopyOnWriteArrayList(); 
/* A thread-safe variant of ArrayList in which all mutative operations
 (add, set, and so on) are implemented by making a fresh copy of the underlying array.*/



    OR
    


    List list = new  Stack(); 

/* The Stack class represents a last-in-first-out (LIFO) stack of objects.*/



    OR
    


    some other List specific implementation. 
    


    List interface defines contract and specific implementation of List can be changed. In this way, interface and implementation are loosely coupled. 
    


    Related SE question:
    


    What does it mean to "program to an interface"?
    
    
    
             
    
                                                        
    
            
            
    
              
                
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