Asked by
Vidya Rani
in
Computers & Technology
at
12:31 PM on November 11, 2008
Dan Dan's Answer
Your question demonstrates a common error made by Java language newcomers. Indeed, even seasoned veterans find it difficult to keep the terms straight.
Java does manipulate objects by reference, and all object variables are references. However, Java doesn't pass method arguments by reference; it passes them by value.
Take the badSwap() method for example:
public void badSwap(int var1, int var2)
{
int temp = var1;
var1 = var2;
var2 = temp;
}
When badSwap() returns, the variables passed as arguments will still hold their original values. The method will also fail if we change the arguments type from int to Object, since Java passes object references by value as well. Now, here is where it gets tricky:
public void tricky(Point arg1, Point arg2)
{
arg1.x = 100;
arg1.y = 100;
Point temp = arg1;
arg1 = arg2;
arg2 = temp;
}
public static void main(String [] args)
{
Point pnt1 = new Point(0,0);
Point pnt2 = new Point(0,0);
System.out.println("X: " + pnt1.x + " Y: " +pnt1.y);
System.out.println("X: " + pnt2.x + " Y: " +pnt2.y);
System.out.println(" ");
tricky(pnt1,pnt2);
System.out.println("X: " + pnt1.x + " Y:" + pnt1.y);
System.out.println("X: " + pnt2.x + " Y: " +pnt2.y);
}
Answered at
12:33 PM on November 11, 2008
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