Value transfer or reference transfer?

The parameter transfer in Java, no matter what you pass, is only a copy passed in. This copy is saved as a local variable of the method in the stack.

If the data type is basic, modifying this value does not affect the variable passed in as a parameter, Because you modify the local variable of the method and it is a copy.

If an object is referenced, it is also the same as a copy, but the copy and the reference passed as a parameter point to the same object in the memory, so you can also operate on that object through this copy. However, if you modify the reference itself, such as directing it to another object in the memory, the reference originally passed as a parameter will not be affected. Therefore, only values are transmitted in Java.

Public class main {

Private Static void change (string S, stringbuffer SB ){

S = "aaaa ";

SB. setlength (0 );

SB. append ("aaaa ");

}

Public static void main (string [] ARGs ){

String S = "BBBB ";

Stringbuffer sb = new stringbuffer ("BBBB ");

Change (S, Sb );

System. Out. Print (S + Sb );

}

} // The output result is "bbbbaaaa" instead of "aaaaaaaa"

Public static void add (stringbuffer X, stringbuffer y ){

X. append (y );

Y = X;

}

Public static void main (string [] ARGs ){

Stringbuffer A = new stringbuffer ("");

Stringbuffer B = new stringbuffer ("B ");

Add (A, B );

System. Out. println (a + "," + B );

} // Output: AB, B