JAVA素数分解

package test;
import java.util.*;

public class test1 {
    public static void main(String[] args){
        long t1 = System.currentTimeMillis();
        System.out.println(factor(100));
        System.out.println(factor(18900));
        System.out.println(factor(72057554846356433L));
        System.out.println(factor(72057554846356487L));
        long t2 = System.currentTimeMillis();
        System.out.println("耗时：" + (t2-t1));
    }
    
    public static Map<Long, Integer> factor(long n){
        Map<Long,Integer> result = new HashMap<Long,Integer>();
        long t = n;
        //先处理偶数，后面处理时 i步进=2，可以节省一半时间
        while (t%2==0){
            result.put(2L,result.get(2L)==null ? 1:result.get(2L)+1);
            t = t/2;
        }
        for (long i=3;i<=Math.sqrt(t);){
            if (t%i==0){
                result.put(i,result.get(i)==null ? 1:result.get(i)+1);
                t = t/i;
            }else{
                i += 2;
            }
        }
        result.put(t,result.get(t)==null ? 1:result.get(t)+1);
        t = 1;
        //return null;
        return result;
    }
}