Pass By Values / Pass By reference

[Sarath Koiloth Ramath]

Hi frnds,


I read the k&B passing the variables and object.But land up with lots of doubts.Can any one please help me to understand the idea behing the pass by reference and pass by values.Is java using pass by values Or java using both.please give a good description

Thank

[Jesper de Jong]

Java is strictly pass-by-value. What confuses people is that Java passes references by value too, which is not the same as pass-by-reference.

See this JavaRanch Campfire Story: Pass-by-Value Please
[ May 22, 2008: Message edited by: Jesper Young ]

[Tusshar Fasate]

Hi Sarath,
Java use only pass by value.
and it doesnt use pass by reference.

here example

static void ranch(int a)
{
int b=b+a
}
in...main

{
int x=9;
ranch(x);

}

here value of x is copied to variable a
and whatever operaions made on a will not be reflected in x.


But its little confusing about array or any object refernce.

static void ranch(Test t)//Test is any class
{

}
in main...
{
Test t1=new Test();

ranch(t1);
....
...}
here also only one object is created and reference is sent to method ranch
so whatever operation made in ranch method will reflect to original object.its also call by value but bit of confusing.


Tushar...
Pune
India

[Sarath Koiloth Ramath]

Hi Tusar,

I think i got it.i will try to explain.

While passing a primitive variable ,Java is passing the copy of the variable.when we pass an object, the reference(that may be an address reference,but pointing to the same object) is passing.hence we say pass by value.So any change made will be reflected in the original object.I am correct...

[fred rosenberger]

Originally posted by Sarath Koiloth Ramath:
So any change made will be reflected in the original object.

it depends on what you mean by 'any change'. if i do this:

MyClass ref = new MyClass(); //create some object and a reference
ref.value = 3;
someMethod(ref);             //pass the reference in
System.out.println("ref.value is " + ref.value);//prints '3'
 

someMethod(MyClass reference){
  reference = new MyClass(); //assign the reference a new object
  reference.value = 2;       //change value of new object
}

[Sarath Koiloth Ramath]

Ok Thanks..I got it...

Thanks once again tushar,Jesper ,and fred...