1亿数据取前1w个数据不超过4秒的java 程序

package net.test;import java.util.Arrays;import java.util.Date;import java.util.Random;public class Top100 {public static void main(String[] args) {find();}public static void find( ) {//int number = 100000000;// 一亿个数int maxnum = 1000000000;// 随机数最大值int i = 0;int topnum = 10000;// 取最大的多少个 Date startTime = new Date();Random random = new Random();int[] top = new int[topnum];for (i = 0; i < topnum; i++) {top[i] = Math.abs(random.nextInt(maxnum));//设置为随机数//top[i] = getNum(i);}buildHeap(top, 0, top.length);// 构建最小堆， top[0]为最小元素for (i = topnum; i < number; i++) {int currentNumber2 = Math.abs(random.nextInt(maxnum));//设置为随机数//int currentNumber2 = getNum(i);// 大于 top[0]则交换currentNumber2  重构最小堆if (top[0] < currentNumber2) {top[0] = currentNumber2;shift(top, 0, top.length, 0); // 构建最小堆 top[0]为最小元素}}System.out.println(Arrays.toString(top));sort(top);System.out.println(Arrays.toString(top));Date endTime = new Date();System.out.println("用了"+(endTime.getTime() - startTime.getTime())+"毫秒"); }public static int getNum(int i){return i;} //构造排序数组public static void buildHeap(int[] array, int from, int len) {int pos = (len - 1) / 2;for (int i = pos; i >= 0; i--) {shift(array, from, len, i);}} /** * @param array top数组 * @param from 开始 * @param len 数组长度 * @param pos 当前节点index * */public static void shift(int[] array, int from, int len, int pos) {// 保存该节点的值 int tmp = array[from + pos];int index = pos * 2 + 1;// 得到当前pos节点的左节点while (index < len)//  存在左节点{if (index + 1 < len&& array[from + index] > array[from + index + 1])// 如果存在右节点{// 如果右边节点比左边节点小，就和右边的比较index += 1;} if (tmp > array[from + index]) {array[from + pos] = array[from + index];pos = index;index = pos * 2 + 1;} else {break;}}// 最终全部置换完毕后 ，把临时变量赋给最后的节点array[from + pos] = tmp;}public static void sort(int[] array){          for(int i = 0; i < array.length - 1; i++){              //当前值当作最小值              int min = array[i];              for(int j = i+1; j < array.length; j++){                  if(min>array[j]){                      //如果后面有比min值还小的就交换                      min = array[j];                      array[j] = array[i];                      array[i] = min;                  }              }          }      }}