java用数组实现栈代码

public class MyStack {
	
	private Object[] arr =new  Object[5];
	private int index = -1;


	public boolean push(Object obj) {
		if (index+1>=arr.length)
			return false;
		arr[++index] = obj;
		return true;
	}


	public Object pop() {
			if (index<0)
				return null;
			return arr[index--];
	}


}