find largest prime factor using java -

i want find largest prime factor of 600851475143.i wrote following code not getting correct answer. please me ...

public class {   public static void main(string[] args) {      int arr[]=new int[25];     int large=0;     long n=600851475143l;     long x=(long) math.sqrt(n);     top:  for(int i=3;i<x;i=i+2)     {       if(n%i==0)       {         n=(long) n/i;         for(int j=0;j<25;j++)         {           arr[j]=i;         }         break top;       }     }     //system.out.println(arr);     int num=arr.length;      for(int i=0;i<num-1;i++)     {       if(arr[i]>arr[i+1])       {         large=arr[i];       }       else       {         large=arr[i+1];        }     }      system.out.println(large);    } } 

public class lpf {     public static void main(string[] args) {         int lpf= 2;         long num = 600851475143l;          while (num > lpf) {             if (num % lpf == 0) {                 num/=lpf;                 lpf = 2;             } else {                 lpf++;             }         }         system.out.println("largest prime factor " + integer.tostring(lpf));     } } 

this simple implementation find largest prime factor of number. way optimize not increment lpf 1 , instead set next highest prime number.