A simple(!) "Call by Value "Example

[Steve Jensen]

Hiya folks.

OK, now i understand conceptually, what passing an argument by the "Call by Value" principle is.

But i've been looking at a small program from a book, which is meant to illustrate it. The code is below:-

 
 
class CallByValue {
  public static void main(String args[]) {
    Test ob = new Test();
    int a = 15, b = 20;
    
    System.out.println("a and b before call: " +
                       a + " " + b);
 
    ob.meth(a, b); 
 
    System.out.println("a and b after call: " +
                       a + " " + b);
  }
}
 
 

I sort of understand how this program works, but i am well and truly stumped as to what the line......

  
ob.meth(a, b); 

......is doing.


What on earth is 'meth', i.e., this hasn't been declared anywhere else in the code!

Why is this so?

Any help would be greatly appreciated.

Cheers in advance

Steve

[Joe Ess]

  
Test ob = new Test();

ob is an instance of class Test. Find where Test is declared and you should find a method named meth.

[Michael Dunn]

You're missing the class Test (meth must be a method of this class)

If I'm reading what it's supposed to depict correctly, here's what would
go with it (and a bit extra, to see the difference)

class Test
{
  public void meth(int num1,int num2,int[] y)
  {
    num1 *= 10;
    num2 *= 10;
    y[0] *= 10;
    y[1] *= 10;
  }
}
class CallByValue
{
  public static void main(String[] args)
  {
    Test ob = new Test();
    int a = 15, b = 20;
    int[] x = {15,20};
    System.out.println("a,b,x0,x1 before call: "+a+" "+b+" "+x[0]+" "+x[1]);
    ob.meth(a,b,x);
    System.out.println("a,b,x0,x1 after call: "+a+" "+b+" "+x[0]+" "+x[1]);
  }
}