Java return does weird things

Question

I have just started learning Java for university with some excercises. I am not new to programming, only to Java. I have followed all instrucions, but Java's return function does some really weird things. I have inserted some debug outputs to better understand the code. CMD.output of the program is included.

I thought that the function would terminate directly after return. But why does it not do in this case?

public class Rekursion {

    public static void main(String[] args) {
        int zahl = 10;
        System.out.println("debugStart");
        boolean even = isEven(zahl);
        System.out.println("debugEnd");

        if (even == true) {
            System.out.println(zahl + " is even");
        } else {
            System.out.println(zahl + " is uneven");
        }
    }

    public static boolean isEven(int n) {
        System.out.println(n);
        if (n > 1) {
            System.out.println("debugx");
            isEven(n - 2);
        }

        if (n == 0) {
            System.out.println("debug1");
            return true;
        } else if (n == 1) {
            System.out.println("debug2");
            return false;
        } else {
            System.out.println("ERROR");
            return false;
        }
    }
}

Output (cmd):

debugStart
10
debugx
8
debugx
6
debugx
4
debugx
2
debugx
0
debug1

Program needs to stop here, normally. But it continues....

ERROR
ERROR
ERROR
ERROR
ERROR
debugEnd
10 is uneven

Answer 1

You should return the recursion call too,

 if(n>1){
     System.out.println("debugx");
     return isEven(n-2);//return at this point
 }

As you haven't returned, your recursive calls are reaching else statements hence returning false.