数组实现堆栈——Java实现

package struct;
 
 
//接口
interface IArrayStack{
    //栈的容量
    int length();
    //栈中元素个数（栈大小）
    int size();
    //取栈顶元素
    Object top();
    //判断栈是否为空
    boolean isEmpty();
    //入栈
    Object pop();
    //出栈
    Object push(Object value);
    //清空栈
    void clear();
}
 
 
//实现接口的StackImpl类
class StackImpl implements IArrayStack{
    static Object[] arr;//数组
    private int top;//标记栈顶位置，并且表示栈的容量大小
    private static int MAXSIZE = 10;//数组的最大长度(常量)
    //构造方法 
    public StackImpl(){
        arr = new Object[MAXSIZE];
        top = 0;
    }
    //求堆栈容量
    public int length() {
        return MAXSIZE;
    }
    //求堆栈中元素的个数，即堆栈大小
    public int size(){
        return top;
    }
    //取栈顶元素
    public Object top() {
        return arr[top];
    }
    //判断堆栈是否为空
    public boolean isEmpty() {
        return (size() == 0);
    }
    //出栈
    public Object pop() {
        if(isEmpty()){
            System.out.println("The Stack is empty");
            return -1;
        }
        Object value = arr[top - 1];
        top--;
        arr[top -1] = null;
        return value;
    }
    //对栈进行扩容（每次扩容一倍）
        public void expand(){
            Object[] largerArr = new Object[size()*2];
            for(int index = 0;index < top;index++){
                largerArr[index] = arr[index];
            }
            arr = largerArr;
            MAXSIZE = arr.length;
        }
    //入栈
    public Object push(Object value) {
        //如果超过入栈元素数组长度
        if(top == arr.length){
            expand();
        }else{
            arr[top] = value;
            top++;    
        }
        return arr;
    }
    //打印堆栈中元素
    public static void print(){
        myPrint1(arr);
    }
    private static void myPrint1(Object[] obj){
        for(int i = 0;i < obj.length;i++){
            System.out.println(obj[i] + " ");
        }
    }
    //清空堆栈
    public void clear() {
        for(int i = top;i > 0;i--){
            arr[i] = null;
            top--;
        }
    }
}
 
 
//测试函数
public class ArrayStack {
    public static void main(String[] args) {
        IArrayStack stack = new StackImpl();
        System.out.println("==================栈中不存在元素测isEmpty函数================");
        System.out.println(stack.isEmpty());
        System.out.println("==================测length函数================");
        System.out.println( stack.length());
        System.out.println("==================测push及print函数================");
        stack.push("lemon");
        stack.push("hah");
        stack.push(1);
        stack.push(9);
        stack.push("lemon");
        stack.push("hah");
        stack.push(1);
        stack.push(9);
        stack.push("lemon");
        stack.push("hah");
        stack.push(1);
        stack.push(9);
        StackImpl.print();
        System.out.println("==================扩容后测length函数================");
        System.out.println(stack.length());
        System.out.println("==================测top函数================");
        System.out.println(stack.top());
        System.out.println("==================测size函数================");
        System.out.println( stack.size());
        System.out.println("==================测pop函数================");
        stack.pop();
        stack.pop();
        System.out.println( stack.size());
        System.out.println("==================栈中存在元素测isEmpty函数================");
        System.out.println(stack.isEmpty());
        System.out.println("==================clear后侧size函数================");
        stack.clear();
        System.out.println( stack.size());
    }
}