Java-大集合拆分为指定大小的小集合

方式一：

public static void main(String[] args) {
    // 每次取集合元素数量
    int x = 5;
    // 集合
    List<String> list = new ArrayList<String>();
    list.add("a");
    list.add("b");
    list.add("c");
    list.add("d");
    list.add("e");
    list.add("f");
    list.add("g");
    list.add("h");
    list.add("i");
    list.add("j");
    /*for (int i = 0; i< 10000 ; i++) {
        list.add(i+"");
    }*/
    long start = System.currentTimeMillis();
    // 如果集合数量小于定义数量 直接发送
    if (list.size() < x) {
      requestPost(list);
      // 反之
    } else {
      // 如果集合不为空
      while (!list.isEmpty()) {
        // 判断集合数量是否小于定义数量
        if (list.size() < x) {
          x = list.size();
        }
        List<String> reqList = list.subList(0, x);
        // System.out.println("1---------" + reqList);
        requestPost(reqList);
        // System.out.println("2---------" + list);
        list.removeAll(reqList);
        // System.out.println("3---------" + list);
      }

    }
    long end = System.currentTimeMillis();
    System.out.println("==============" + (end - start));

  }

  private static void requestPost(List<String> list) {
    System.out.println(list);
  }

方式二：

/**
     * 拆分集合
     * @param <T>
     * @param resList  要拆分的集合
     * @param count    每个集合的元素个数
     * @return  返回拆分后的各个集合
     */
    public static  <T> List<List<T>> split(List<T> resList,int count){
        
        if(resList==null ||count<1)
            return  null ;
        List<List<T>> ret=new ArrayList<List<T>>();
        int size=resList.size();
        if(size<=count){ //数据量不足count指定的大小
            ret.add(resList);
        }else{
            int pre=size/count;
            int last=size%count;
            //前面pre个集合，每个大小都是count个元素
            for(int i=0;i<pre;i++){
                List<T> itemList=new ArrayList<T>();
                for(int j=0;j<count;j++){
                    itemList.add(resList.get(i*count+j));
                }
                ret.add(itemList);
            }
            //last的进行处理
            if(last>0){
                List<T> itemList=new ArrayList<T>();
                for(int i=0;i<last;i++){
                    itemList.add(resList.get(pre*count+i));
                }
                ret.add(itemList);
            }
        }
        return ret;
        
    }

 

/**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        List<String> resList=Arrays.asList("0","1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","21","22","23","24","25","26","27","28","29","30","31","32","33","34","35","36","37","38","39","40","41","42","43","44","45","46","47","48","49","50","51","52","53","54","55","56","57","58","59","60","61","62","63","64","65","66","67","68","69","70","71","72","73","74","75","76","77","78","79","80","81","82","83","84","85","86","87","88","89","90","91","92","93","94","95","96","97","98","99");
        List<List<String>> ret=split(resList,10);
        
        for(int i=0;i<ret.size();i++){
            System.out.println(ret.get(i));
        }
        
    
    }

经本人测试，方式二的效率更高。