java实现栈（数组和链表两种实现方式）_java stack数组和链表

栈的实现

栈是一种先进后出的数据结构, 

首先用数组实现，底层使用数组：

public class MyArrayStack<T> {
	private Object[] objs = new Object[16];
	private int size = 0;
 
 
	public boolean isEmpty() {
		return size == 0;
	}
 
	
	public void clear() {
		// 将数组中的数据置为null, 方便GC进行回收
		for (int i = 0; i < size; i++) {
			objs[size] = null;
		}
		size = 0;
	}
 
	
	public int length() {
		return size;
	}
 
	
	public boolean push(T data) {
		// 判断是否需要进行数组扩容
		if (size >= objs.length) {
			resize();
		}
		objs[size++] = data;
		return true;
	}
 
	/**
	 * 数组扩容
	 */
	private void resize() {
		Object[] temp = new Object[objs.length * 3 / 2 + 1];
		for (int i = 0; i < size; i++) {
			temp[i] = objs[i];
			objs[i] = null;
		}
		objs = temp;
	}
 
	
	public T pop() {
		if (size == 0) {
			return null;
		}
		return (T) objs[--size];
	}
 
	
	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append("MyArrayStack: [");
		for (int i = 0; i < size; i++) {
			sb.append(objs[i].toString());
			if (i != size - 1) {
				sb.append(", ");
			}
		}
		sb.append("]");
		return sb.toString();
	}
}  

栈的链表实现，底层使用链表：

public class MyLinkedStack<T> {
	/**
	 * 栈顶指针
	 */
	private Node top;
	/**
	 * 栈的长度
	 */
	private int size;
	
	public MyLinkedStack() {
		top = null;
		size = 0;
	}
	
	
	public boolean isEmpty() {
		return size == 0;
	}
	
	
	public void clear() {
		top = null;
		size = 0;
	}
	
	
	public int length() {
		return size;
	}
	
	
	public boolean push(T data) {
		Node node = new Node();
		node.data = data;
		node.pre = top;
		// 改变栈顶指针
		top = node;
		size++;
		return true;
	}
	
	
	public T pop() {
		if (top != null) {
			Node node = top;
			// 改变栈顶指针
			top = top.pre;
			size--;
			return node.data;
		}
		return null;
	}
	
	/**
	 * 将数据封装成结点
	 */
	private final class Node {
		private Node pre;
		private T data;
	}
}