java顺序栈功能通过数组实现

1.定义栈接口

public interface Stack<T> {
//返回栈的大小
    public int size();
//判断栈是否为空
    public boolean isEmpty();
//入栈
    public void push(T t);
//出栈
    public Object pop() throws StackEmptyException;
//返回栈顶元素
    public Object peek() throws StackEmptyException ;
}

2.自定义异常

public class StackEmptyException extends RuntimeException {
//新增栈为空的异常类
    public StackEmptyException(String eMeaasge ){
        super(eMeaasge);
    }
}

3.数组实现栈接口

public class StackArray<T> implements Stack<T> {
//栈的初始容量为2；
    private final int LEN=2;
//    定义栈的指针；
    private int top;
//    栈以数组实现
    private T[] elements;
//    构造方法进行初始化
    public StackArray(){
        top=-1;
        elements= (T[]) new Object[LEN];
    }

    @Override
    public int size() {
        return top+1;
    }

    @Override
    public boolean isEmpty() {
        return top<0;
    }

    @Override
    public void push(T t) {
        if(this.size()==elements.length){
         this.expandSize();
        }
//        ++top，先自增，再赋值
         elements[++top]=t;
    }

    @Override
    public Object pop() throws StackEmptyException {
        if(this.isEmpty()){
            throw new StackEmptyException("当前栈为空，无法出栈");
        }
        Object obj = elements[top];
//        top--，先赋值，再自减
        elements[top--]=null;
        return obj ;
    }

    @Override
    public Object peek() throws StackEmptyException {
        if(this.isEmpty()){
            throw new StackEmptyException("当前栈为空，无内容");
        }
        return elements[top];
    }
//栈容量扩容
    public void expandSize(){
        T[] a= (T[]) new Object[elements.length *2];
        for(int i=0;i<elements.length;i++){
            a[i]=elements[i];
        }
        elements=a;
    }
}

4.测试

public class Main {

    public static void main(String[] args) {
        StackArray<Integer> stackArray = new StackArray<Integer>();
        System.out.println(stackArray.size());
       /* stackArray.pop();*/
        stackArray.push(1);
        stackArray.push(2);
        stackArray.push(5);
        stackArray.push(6);
        System.out.println(stackArray.size());
        System.out.println(stackArray.peek());


    }
}

5.测试结果