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  • Java学习随笔1:Java是值传递还是引用传递?

    Java always passes arguments by value NOT by reference.


    Let me explain this through an example:

    public class Main{
         public static void main(String[] args){
              Foo f = new Foo("f");
              changeReference(f); // It won't change the reference!
              modifyReference(f); // It will modify the object that the reference variable "f" refers to!
         }
         public static void changeReference(Foo a){
              Foo b = new Foo("b");
              a = b;
         }
         public static void modifyReference(Foo c){
              c.setAttribute("c");
         }
    }
    

    I will explain this in steps:

    1. Declaring a reference named f of type Foo and assign it to a new object of type Foo with an attribute "f".

      Foo f = new Foo("f");
      

      enter image description here

    2. From the method side, a reference of type Foo with a name a is declared and it's initially assigned to null.

      public static void changeReference(Foo a)
      

      enter image description here

    3. As you call the method changeReference, the reference a will be assigned to the object which is passed as an argument.

      changeReference(f);
      

      enter image description here

    4. Declaring a reference named b of type Foo and assign it to a new object of type Foo with an attribute "b".

      Foo b = new Foo("b");
      

      enter image description here

    5. a = b is re-assigning the reference a NOT f to the object whose its attribute is "b".

      enter image description here


    6. As you call modifyReference(Foo c) method, a reference c is created and assigned to the object with attribute "f".

      enter image description here

    7. c.setAttribute("c"); will change the attribute of the object that reference c points to it, and it's same object that reference f points to it.

      enter image description here

    I hope you understand now how passing objects as arguments works in Java :)

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  • 原文地址:https://www.cnblogs.com/mengrennwpu/p/4889015.html
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