package DSA.Stack; import java.util.EmptyStackException; public class StackArray { private int[] stack; private int top; private Object lock; public StackArray(int capacity) { this.stack = new int[capacity]; this.top = -1; this.lock = new Object(); } public boolean isEmpty() { return this.top < 0; } private void push(int value) { synchronized (lock) { if (this.top + 1 == this.stack.length) { throw new RuntimeException("stack is full"); } this.top++; this.stack[this.top] = value; } } private int pop() { synchronized (new Object()) { if (isEmpty()) { throw new EmptyStackException(); } int result = this.stack[this.top]; this.stack[this.top] = Integer.MAX_VALUE; this.top--; return result; } } public int peek() { if (isEmpty()) { throw new EmptyStackException(); } return this.stack[this.top]; } private void printStack() { if (isEmpty()) { throw new EmptyStackException(); } for (int i = this.top; i > 0; i--) { System.out.println(this.stack[i]); } } public static void main(String[] args) { StackArray ll = new StackArray(6); ll.push(1); ll.push(2); ll.push(3); ll.push(5); ll.push(6); ll.push(7); ll.printStack(); System.out.println("pop: " + ll.pop()); ll.printStack(); } }