大数据处理算法一：Bitmap算法

java 代码实现

import java.util.BitSet;
/**
 * 大数据处理算法一，bitmap算法
 * @author JYC506
 *
 */
public class Bitmap {

 byte[] tem;

 public Bitmap(int length) {
  this.tem = new byte[length];
 }

 public void add(int num) {
  if (num < tem.length) {
   if (tem[num] != 1) {
    tem[num] = 1;
   }
  }
 }

 public boolean contain(int num) {
  if (num < tem.length) {
   if (tem[num] == 1) {
    return true;
   }
  }
  return false;
 }

 public static void main(String[] args) {
  /*运行前内存*/
  long beforeMemory = Runtime.getRuntime().totalMemory();
  long start1=System.currentTimeMillis();
  BitSet set = new BitSet(2000000000);
  for (int i = 0; i < 2000000000; i++) {
   /*假设898989这个数不在20亿个数里面*/
   if (i != 898989) {
    set.set(i, true);
   }
  }
  /*创建20亿个数后所占内存*/
  long afterMemory = Runtime.getRuntime().totalMemory();
  long end1=System.currentTimeMillis();
  System.out.println("总共内存使用:" + (afterMemory - beforeMemory) / 1024 / 1024 + "MB");
  System.out.println("存入内存耗时:"+(end1-start1)+"毫秒");
  long start2 = System.currentTimeMillis();
  boolean isExit1=set.get(898989);
  boolean isExit2=set.get(900000);
 
  long end2 = System.currentTimeMillis();
  /*输出在20亿个数中判断898989是否包含在里面*/
  System.out.println(isExit1);
  System.out.println("20个亿中"+(isExit1?"包含":"不包含")+898989);
  System.out.println("20个亿中"+(isExit2?"包含":"不包含")+900000);
  System.out.println("查询用时:"+(end2 - start2)+"毫秒");
 }

}

原文：http://blog.csdn.net/h348592532/article/details/45362661