Java access variables in arguments

Question

I would like to be able to access a variable passed to my method. I know C might have has some kind of way to pass the address of something as an argument, then refer to that as a pointer and be able to use the variable. Anyway, here's an example.

void myFunction(address to variable) {
    *variable = "example";
}

Then call it as:

myFunction(&somevariable);

Passing by reference is the term. And yes, the mutable objects are just like that. — ppeterka, Mar 04 '13 at 14:36

score 5 · Accepted Answer · answered Mar 04 '13 at 14:37

There is no way to pass arguments by reference or by pointer in Java, so the only way to achieve the effect that you would like is passing a mutable object, and changing its value inside the method that you call:

public class ChangeableInt {
    private int number;
    public ChangeableInt(int value) {number = value;}
    public int get() {return number;}
    public void set(int value) {number = value;}
}

With this class in hand, you can do this:

void myFunction(ChangeableInt arg) {
   arg.set(42);
}
...
ChangeableInt val = new ChangeableInt(123);
myFunction(val);
System.out.println(val.get()); // prints 42

score 1 · Answer 2 · answered Mar 04 '13 at 14:39

1

What you need is a simple wrapper template class...

class ObjWrapper<T> {
  T value;

  void setValue(T val) {
    value=val;
  }

  T getValue() {
    return value;
  }
}

answered Mar 04 '13 at 14:39

Dariusz

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score 0 · Answer 3 · answered Mar 04 '13 at 14:45

something like

 class Myclass{
    int x=15;

    System.out.println(x) //15

    public static void main(String... ){

    Myclass obj = new Myclass()
    Myclass newRef =  method(obj)
    System.out.println(newRef.x)   //20




    }
   static Myclass method(Myclass ref){
       ref.x=20

    return ref
  }  
    }//class

Note that in 'obj' is a reference to the object resides somewhere in heap.

Java access variables in arguments

3 Answers3

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