用固定长度的数组实现stack queue

package my_basic.class_3;

/**
 * 用数组结构实现大小固定的队列和栈
 */
public class Code_01_Array_stack_queue {
    
    public static class ArrayStack{
        private Integer[] arr;
        private Integer size;
        
        public ArrayStack(int initSize) {
            if (initSize < 0) {
                throw new IllegalArgumentException("The init size is less than 0");
            }
            arr = new Integer[initSize];
            size=0;
            
        }
        
        public Integer peek() {
            if (size == 0) {
                return null;
            }
            return arr[size-1];
            
        }
        public void push(int num) {
            if (size == arr.length) {
                throw new ArrayIndexOutOfBoundsException("the stack is full");
            }
            arr[size++] = num;
        }
        public Integer pop() {
            if (size == 0) {
                throw new ArrayIndexOutOfBoundsException("the stack is empty");
            }
            size--;
            return arr[size];
        }
    
}

    public static class ArrayQueue{
        private Integer[] arr;
        private int size;
        private int first;
        private int last;
        
        public ArrayQueue(int initSize) {
            if (initSize < 0 ) {
                throw new IllegalArgumentException("The init size is less than 0");
            }
            arr = new Integer[initSize];
            size=0;
            first=0;
            last=0;
        }
        public Integer peek() {
            if (size == 0) {
                return null;
            }
            return arr[first];
        }
        public void push(int obj) {
            if (size == arr.length) {
                throw new ArrayIndexOutOfBoundsException("the queue is full");
            }
            size++;
            arr[last] = obj;
            last = (last == arr.length-1) ? 0 : last++;
        }
        public Integer poll() {
            if (size == 0) {
                throw new ArrayIndexOutOfBoundsException("the queue is empty");
            }
            size--;
            int res = first;
            first = (first == arr.length-1)? 0 : first++;
            return arr[res];
        }
        
    }
    
    public static void main(String[] args) {
        
        
    }
        
    
}