Stack.java

/* Java program to implement basic stack
operations */
class Stack {
  static final int MAX = 1000;
  int top;
  int a[] = new int[MAX]; // Maximum size of Stack

  boolean isEmpty() { return (top < 0); }
  Stack() { top = -1; }

  boolean push(int x) {
    if (top >= (MAX - 1)) {
      System.out.println("Stack Overflow");
      return false;
    } else {
      a[++top] = x;
      System.out.println(x + " pushed into stack");
      return true;
    }
  }

  int pop() {
    if (top < 0) {
      System.out.println("Stack Underflow");
      return 0;
    } else {
      int x = a[top--];
      return x;
    }
  }

  int peek() {
    if (top < 0) {
      System.out.println("Stack Underflow");
      return 0;
    } else {
      int x = a[top];
      return x;
    }
  }
}

// Driver code
class Main {
  public static void main(String args[]) {
    Stack s = new Stack();
    s.push(10);
    s.push(20);
    s.push(30);
    System.out.println(s.pop() + " Popped from stack");
  }
}