[tomjas]

Originally Posted by alykins

for your properties (I think called 'fields' in Java) you generally just do a return of the variable...

public int getNum()
{
  return i;
}

you usually have/use variables in methods because you are not always sure what the variable will be

private int computeNewNum(int varibleNumber)
{
  i = (variableNumber * i)
  return i;
}
// input 2
// output 20
// input 5
// output 100

if field "i" is 10 and you pass 2, it will become 20; then pass a 5- 100 and so on. That is the reason you use variables. each return would be different depending what you passed it- also i is being set. You could also use i as a static variable and do something like

private int computeNewNum(int variableNumber)
{
  return (i * variableNumber);
}
// input 2
// output 20
// input 5
// output 50

see? the second one doesn't assign i.

That is ok - all above is true and I know what variables are and how they work. My question is - what is return statement for (apart from quiting method). Let's rewrite my example to make this method protected/private and do not initialize i.

public class Main {
    int i;

    protected void num(int i, int a) {
        this.i = i * a;
    }

    public static void main (String [] args) {
        Main n = new Main();
        n.num(10,5);
        System.out.println(n.i);
    }
}

It works and shows that whatever we do to "i" value it is not necessary to return it.

making a field private means that only that object can access it and change it via method.

public class Demo
{
  private int i = 10;

  public Demo(){...}
  
  public void seti(int variableNumber)
  {
    i = variableNumber;
  }

  public int geti()
  {
    return i;
  }
}

you can't access i in any other class. You can call the Demo.seti() and 'change' i, but you are not accessing it directly. You can throw in validation @ this point.

public void seti(int variableNumber)
{
  if(variableNumber >= 0 && variableNumber <= 100)
    i = variableNumber;
  else
    throw new exception();
}

note* syntax's might be off-

So once again - the only reason for writing the whole method (which job is just to return value) is to make fields and method be private/protected in other classes than the class in which we instantiate object?