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:

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");
```
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)
```
As you call the method changeReference, the reference a will be assigned to the object which is passed as an argument.
```
changeReference(f);
```
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");
```
a = b is re-assigning the reference a NOT f to the object whose its attribute is "b".
As you call modifyReference(Foo c) method, a reference c is created and assigned to the object with attribute "f".
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.

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

巴特西

Java学习随笔1：Java是值传递还是引用传递？

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