Java 实现栈，队列

package base.structure;

/**
 * @program: Algorithm4J
 * @description: 实现一个Stack
 * @author: Mr.Dai
 * @create: 2018-12-06 15:25
 **/
public class Stack<T> {

    // point
    int n;
    // arrays implement
    T [] elements;

    // 初始化一个栈
    public   Stack(){
        n=0;
        elements= ((T[]) new Object[20]);
    }

    public  void push(T item){
        if(n==elements.length){
            resize(elements.length*2);
        }
        elements[n++]=item;
    }

    // 调控数组大小
    private void resize(int i) {
        T[] arrays=(T[])new Object[i];
        System.arraycopy(elements,0,arrays,0,elements.length);
        elements=arrays;
    }

    public T pop(){
        if(isEmpty()) throw new ArrayIndexOutOfBoundsException();
        T x=elements[n-1];
        n--;
        return x;
    }
    public boolean isEmpty(){
        return n==0;
    }
    public  int Size(){return n;}

}

 队列

package base.structure;

/**
 * @program: Algorithm4J
 * @description: 实现队列
 * @author: Mr.Dai
 * @create: 2018-12-06 15:37
 **/
public class Queue<T> {

    // tail point
    private int tailp;
    // head point
    private int headp;
    // save arrays
    private T [] elements;

    public Queue(){
        tailp=0;
        elements=(T[])new Object[20];
    }

    // 入队
    public void enqueue(T item){
        if(tailp==elements.length){
            resize(elements.length*2);
        }
        elements[tailp++]=item;
    }
    // 调控数组大小
    private void resize(int i) {
        T[] arrays=(T[])new Object[i];
        System.arraycopy(elements,0,arrays,0,elements.length);
        elements=arrays;
    }
    // 出队
    public T dequeue(){
        if (isEmpty()) throw new ArrayIndexOutOfBoundsException();
        T val=elements[headp];
        headp++;
        return val;
    }

    boolean isEmpty(){
        return headp==tailp;
    }

    public int Size(){
        return tailp-headp;
    }

}