按批次处理list数据的两种方法

  • 2018-01-26
  • 浏览 (179)

按批次处理list数据的两种方法,主要应用于list存储数据过多,为防止内存溢出等情况不能对list整体进行操作。

import java.util.ArrayList;
import java.util.List;

public class DealListByBatch {
     
    /**
     * 通过list的     subList(int fromIndex, int toIndex)方法实现
     * @param sourList 源list
     * @param batchCount 分组条数
     */
    public static void dealBySubList(List<Object> sourList, int batchCount){
        int sourListSize = sourList.size();
        int subCount = sourListSize%batchCount==0 ? sourListSize/batchCount : sourListSize/batchCount+1;
        int startIndext = 0;
        int stopIndext = 0;
        for(int i=0;i<subCount;i++){
            stopIndext = (i==subCount-1) ? stopIndext + sourListSize%batchCount : stopIndext + batchCount;
            List<Object> tempList = new ArrayList<Object>(sourList.subList(startIndext, stopIndext)); 
            printList(tempList);
            startIndext = stopIndext;
        }
    }
     
    /**
     * 通过源list数据的逐条转移实现
     * @param sourList 源list
     * @param batchCount 分组条数
     */
    public static void dealByRemove(List<Object> sourList, int batchCount){
        List<Object> tempList = new ArrayList<Object>();
        for (int i = 0; i < sourList.size(); i++) {  
            tempList.add(sourList.get(i));
            if((i+1)%batchCount==0 || (i+1)==sourList.size()){
                printList(tempList);
                tempList.clear();
            }
        }
    }
     
    /**
     * 打印方法 充当list每批次数据的处理方法
     * @param sourList
     */
    public static void printList(List<Object> sourList){
        for(int j=0;j<sourList.size();j++){
            System.out.println(sourList.get(j));
        }
        System.out.println("------------------------");
    }
     
    /**
     * 测试主方法
     * @param args
     */
    public static void main(String[] args) {
        List<Object> list = new ArrayList<Object>();  
        for (int i = 0; i < 91; i++) {  
            list.add(i);  
        }  
        long start = System.nanoTime();
        dealBySubList(list, 10);
        dealByRemove(list, 10);
        long end = System.nanoTime();
        System.out.println("The elapsed time :" + (end-start));
         
    }
}

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