Question

public class cash
{
    public void test(int a)
    {
        if(a<5)
        {
            System.out.print(a+" ");
            test(++a);
            System.out.println(a);
        }
        System.out.println("fin");
    }
    public static void main(String[] argsc)
    {
        cash c=new cash();       
        c.test(1);
    }
}

The output:

1 2 3 4 fin
5
fin
4
fin
3
fin
2
fin

why ? I think the output should be 1 2 3 4 fin.
thank you very much.

Answer 1

Ok, so this is your recursive method:

public void test(int a)
{
    if(a<5)
    {
        System.out.print(a+" ");
        test(++a);
        System.out.println(a);
    }
    System.out.println("fin");
}

every statement in this method gets invoked when you call it. lets think about the semantics in this method.
This list describes in words, what your method does:

• check if a<5. if true
  • print out a.
  • call test(++a),
  • print out the incremented a
• print out "fin"

Your first problem is, that you always (during every invocation of test()) print out "fin". put it in an else {...} block to fix it.

Your second problem is, that you print out the incremented value of a, thats why you get your output. remove the second println-statement (System.out.println(a);) to fix that.

The correct implementation of your method would look like this:

public void test(int a)
{
    if(a<5) {
        System.out.print(a);
        test(++a);
    } else {
        System.out.println("fin");
    }
}