Uninitialized Object vs Object Initialized to NULL

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自闭症患者
自闭症患者 2020-11-27 13:34

I\'m working in Java.

I commonly setup some objects as such:

public class Foo {
    private SomeObject someName;

    // do stuff

    public void so         


        
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  • 2020-11-27 13:54

    If an Object reference has been declared but not instantiated, its value is null.

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  • 2020-11-27 14:09
    namespace Design
         {
                  class Program
                  {
    
                    static void Main(string[] args)
                    {
                      Logger obj1;   // By Default, the value of obj1 is null
                      Logger obj2 = new Logger();  // By Default the value of obj2 is 
                                                   // Design.Logger which is not null
                      Console.WriteLine(obj2); 
                      Console.Read();
                    }
                  }
    
         class Logger
               {
                 public Logger()
                  {
                     Console.writeline("Called");
                  }   
                }
            }
    
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  • 2020-11-27 14:17

    Correct, both static and instance members of reference type not explicitly initialized are set to null by Java. The same rule applies to array members.

    From the Java Language Specification, section 4.12.5:

    Initial Values of Variables

    Every variable in a program must have a value before its value is used:

    Each class variable, instance variable, or array component is initialized with a default value when it is created

    [...] For all reference types, the default value is null.

    Note that the above rule excludes local variables: they must be initialized explicitly, otherwise the program will not compile.

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