An implementation of a Stack in java

Stack.java

public class Stack {
  int s[] = new int[100];
	int top = -1;

	boolean isEmpty(Stack s) {
		if (s.top < 0) {
			return true;
		} else
			return false;
	}

	void push(Stack s, int x) {
		s.top = s.top + 1;
		s.s[s.top] = x;
	}

	int pop(Stack s, int x) {
		if (s.isEmpty(s)) {
			System.out.println("Stack is empty");
			return -1;
		} else {
			s.top = s.top - 1;
			return s.s[s.top + 1];.
		}
	}
}