java.lang.StackOverflowError？ 在java中

Question

i get this " java.lang.StackOverflowError " when i run the code but the problem come when i put a big number like (7,10)

this is the code that i write

The code for calculate The Ackermann Function

public static void main(String[] args) {
    int m, n, s;
    Scanner maher = new Scanner(System.in);
    System.out.println(" the code for calculate The Ackermann Function ");
    System.out.println(" Enter first number M");
    m = maher.nextInt();
    System.out.println(" Enter Second number N");
    n = maher.nextInt();
    System.out.println("A(" + m + " , " + n + ") = " + Ack(m, n) + " \n");
}
public static int Ack(int m, int n) {
    if (m == 0) {
        return n + 1;
    }
    if (m != 0 && n == 0) {
        return Ack(m - 1, 1);
    }
    if (m != 0 && n != 0) {
        return Ack(m - 1, Ack(m, n - 1));
    }
    return 0;
    // This code written by Maher Al Shammari 212542270 // KFU
}

I try to change the type to long but the problem doesn't solve ,,,,

Answer 1

You have created "endless" or at least "too deep" recursion. This is the problem here.

Not to talk of the fact that this function is known to grow very very very quickly. So you will need BigInteger for it (not int, not long). Probably though even BigInteger will not get you too far.

Answer 2

• Stack overflow means too many nested method calls .

• Your logic seems right, its surely due many recursive calls involved.

• Anyways, I think you should be happy to see result for ACK(4, 4) .

• ACK(7, 10) - really? asking too much... its like calling NQueens(16) :P

Answer 3

You can try manipulating the JVM stack size. I'm not sure that this will help in the end, but if you have a machine with a lot of memory, you can increase both the stack and heap and push the failure out further.

The default stack size is 384KB. You manipulate it using the -Xss parameter to the JVM. For example, -Xss512k sets the stack size to 512KB.