利用java链表实现栈

/**
 * 定义一个链表的节点
 *
 * @author VicterTian
 * @version V1.0
 * @Date 2019/1/21
 */
class NodeForStack<E> {
  NodeForStack<E> next = null;
  E data;

  NodeForStack(E data) {
    this.data = data;
  }
}
/**
 * 通过链表实现栈
 *
 * @author VicterTian
 * @version V1.0
 * @Date 2019/1/21
 */
public class MyStackByLinkedList<E> {
  private NodeForStack<E> top = null;

  Boolean isEmpty() {
    return top == null;
  }

  void push(E data) {
    NodeForStack<E> newNode = new NodeForStack<>(data);
    newNode.next = top;
    top = newNode;
  }

  E pop() {
    if (this.isEmpty()) {
      return null;
    }
    E data = top.data;
    top = top.next;
    return data;
  }
   E peek(){
    if (this.isEmpty()){
      return null;
    }
    return top.data;
  }
  /**
   * 测试
   */
  public static void main(String[] args) {
    MyStackByLinkedList<Integer> myStack = new MyStackByLinkedList<>();
    myStack.push(1);
    myStack.push(2);
    System.out.println("myStack.peek() = " + myStack.peek());
    System.out.println("myStack.pop() = " + myStack.pop());
    System.out.println("myStack.pop() = " + myStack.pop());
  }
}