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) {

     }

 }