栈_Java

顺序栈：

import java.util.Arrays;

public class SequenceStack<T> {

    private int DEFAULT_SIZE = 10;
    private int capacity;
    private int capacityIncrement = 0;
    private Object[] elementData;
    private int size = 0;
    
    public SequenceStack(){
        capacity = DEFAULT_SIZE;
        elementData = new Object[capacity];
    }
    
    public SequenceStack(T element){
        this();
        elementData[0] = element;
        size++;
    }
    
    public SequenceStack(T element , int initSize){
        this.capacity = initSize;
        elementData = new Object[capacity];
        elementData[0] = element;
        size++;
    }
    
    public SequenceStack(T element , int initSize , int capacityIncrement){
        this.capacity = initSize;
        this.capacityIncrement = capacityIncrement;
        elementData = new Object[capacity];
        elementData[0] = element;
        size++;
    }
    
    public int length(){
        return size;
    }
    
    public void push(T element){
        ensureCapacity(size + 1);
        elementData[size++] = element;
    }

    private void ensureCapacity(int minCapacity) {
        if(minCapacity > capacity){
            if(capacityIncrement > 0){
                while(capacity < minCapacity){
                    capacity += capacityIncrement;
                }
            } else {
                while(capacity < minCapacity){
                    capacity <<= 1;
                }
            }
            elementData = Arrays.copyOf(elementData, capacity);
        }
    }
    
    @SuppressWarnings("unchecked")
    public T pop(){
        T oldValue = (T)elementData[size-1];
        elementData[--size] = null;
        return oldValue;
    }
    
    @SuppressWarnings("unchecked")
    public T peek(){
        return (T)elementData[size-1];
    }
    
    public boolean empty(){
        return size == 0;
    }
    
    public void clear(){
        Arrays.fill(elementData, null);
        size = 0;
    }
    
    public String toString(){
        if(size == 0){
            return "[]";
        } else {
            StringBuilder sb = new StringBuilder("[");
            for(int i = size - 1 ; i > -1 ; i--){
                sb.append(elementData[i].toString() + ", ");
            }
            int len = sb.length();
            return sb.delete(len-2, len).append("]").toString();
        }
    }
}

测试代码：

public class SequenceStackTest {

    public static void main(String[] args) {
        SequenceStack<String> stack = new SequenceStack<String>();
        stack.push("aaaa");
        stack.push("bbbb");
        stack.push("cccc");
        stack.push("dddd");
        System.out.println(stack);
        System.out.println("访问栈顶元素： " + stack.peek());
        System.out.println("第一次弹出栈顶元素： " + stack.pop());
        System.out.println("第二次弹出栈顶元素： " + stack.pop());
        System.out.println("两次pop之后的栈： " + stack);
    }
}

测试结果：

[dddd, cccc, bbbb, aaaa]
访问栈顶元素： dddd
第一次弹出栈顶元素： dddd
第二次弹出栈顶元素： cccc
两次pop之后的栈： [bbbb, aaaa]

链表栈：

public class LinkStack<T> {
    private class Node{
        private T data;
        private Node next;
        
        @SuppressWarnings("unused")
        public Node(){    
        }
        
        public Node(T data , Node next){
            this.data = data;
            this.next = next;
        }
    }
    
    private Node top;
    private int size;
    
    public LinkStack(){
        top = null;
    }
    
    public LinkStack(T element){
        top = new Node(element , null);
        size++;
    }
    
    public int length(){
        return size;
    }
    
    public void push(T element){
        top = new Node(element , top);
        size++;
    }
    
    public T pop(){
        Node oldTop = top;
        top = top.next;
        oldTop.next = null;
        size--;
        return oldTop.data;
    }
    
    public T peek(){
        return top.data;
    }
    
    public boolean empty(){
        return size == 0;
    }
    
    public void clear(){
        top = null;
        size = 0;
    }
    
    public String toString(){
        if(empty()){
            return "[]";
        } else {
            StringBuilder sb = new StringBuilder("[");
            for(Node current = top ; current != null ; current = current.next){
                sb.append(current.data.toString() + ", ");
            }
            int len = sb.length();
            return sb.delete(len-2, len).append("]").toString();
        }
    }
}

测试代码：

public class LinkStackTest {

    public static void main(String[] args) {
        LinkStack<String> stack = new LinkStack<String>();
        stack.push("aaaa");
        stack.push("bbbb");
        stack.push("cccc");
        stack.push("dddd");
        System.out.println(stack);
        System.out.println("访问栈顶元素： " + stack.peek());
        System.out.println("第一次弹出栈顶的元素： " + stack.pop());
        System.out.println("第二次弹出栈顶的元素： " + stack.pop());
        System.out.println("两次pop之后的栈： "  + stack);
    }
}

测试结果：

[dddd, cccc, bbbb, aaaa]
访问栈顶元素： dddd
第一次弹出栈顶的元素： dddd
第二次弹出栈顶的元素： cccc
两次pop之后的栈： [bbbb, aaaa]