限制类实例化次数

 

public class NewClassCount {

 private static final SingleClassIterator instances = new SingleClassIterator();
 
 private NewClassCount(){
  
 }
 
 public static NewClassCount getInstance(){
  return instances.next();
 }
 
 private static class SingleClassIterator{
  private static final int newClassNumber = 4;//实例化次数
  private NewClassCount[] newClassCountArray = new NewClassCount[newClassNumber];
  private int counter;//实例计数器
  
  public SingleClassIterator() {
   //创建有限个实例对象，保存数组中
   for(int i = 0; i < newClassNumber; i++){
    newClassCountArray[i] = new NewClassCount();
   }
  }
  
  public NewClassCount next(){
   //若实例次数=最大数量，计数器设置为0
   if(counter == newClassNumber){
    counter = 0;
   }
   NewClassCount instance = newClassCountArray[counter];
   System.out.println("counter=" + counter);
   counter++;
   return instance;
  }
 }

 public static void main(String[] args) {
  NewClassCount.getInstance();
  NewClassCount.getInstance();
  NewClassCount.getInstance();
  NewClassCount.getInstance();
  NewClassCount.getInstance();
  NewClassCount.getInstance();

 }

输出：

        counter=0
        counter=1
        counter=2
        counter=3
        counter=0
        counter=1