Different instances of value types and reference types in Java (iii)

There is no doubt that the difference between a function pass and a function reference is that it is possible to manipulate an object by passing a copy of the data to the reference.

But what most people ignore is that a reference is actually a copy of a reference.

Examples are as follows:

1 class Number2 {3      Public intnum;4 }5  Public classTopcoder6 {7      Public Static voidMain (string[] args)8     {9Number a=NewNumber ();TenA.num=1; OneNumber b=NewNumber (); Ab.num=2; - Swap (A, b); -System.out.println (a.num+ "" +b.num); the     } -      -     Static voidSwap (number A,number b) -     { + Number temp; -temp=b; +b=A; AA=temp; at     } -}

Output is:

1 2

The analysis is as follows:

Before swap

Reference a----------->number (num:1)

Reference b----------->number (num:2)

In swap

Because the function simply passes a copy of the reference and does not have any effect on references A and B, it can be ignored.

After swap

Since the SWAP function has no effect on references A and B, and the swap function does not change the object content, there is no change

Different instances of value types and reference types in Java (iii)