DataStructure_Algorithm/src/queue/Stack.java at master · java4fun/DataStructure_Algorithm

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package queue;

public class Stack {

private int[] items = new int[100];

private int top = -1; //index to keep track of the topmost element

public boolean isEmpty() {

return top < 0;

}

public void push(int item) {

if (top == items.length-1)

throw new RuntimeException("Stack is full");

items[++top] = item;

}

/**

* Returns the topmost item and removes it

* @return

public int pop() {

if (isEmpty())

throw new RuntimeException("Stack is empty");

return items[top--];

}

/**

* Returns the topmost item without removing it

* Peek and Pop methods should ideally be invoked after checking that the stack is not empty

* either in a 'if' condition or a 'while' loop

* @return

public int peek() {

if (isEmpty())

throw new RuntimeException("Stack is empty");

return items[top];

}

public static void main(String[] args) {

Stack stack = new Stack();

System.out.println(stack.isEmpty());

stack.push(5);

stack.push(4);

stack.push(6);

stack.push(10);

System.out.println(stack.isEmpty());

System.out.println(stack.peek());

System.out.println(stack.pop());

System.out.println(stack.peek());

System.out.println(stack.pop());

}

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