arrays - Decrease run time of this java program -

i have made program input array, , find product of 3 largest numbers of array such that:

the array constitutes of sub-arrays consisting of index increased 1 @ time.

that is, array of 10 elements, find product considering first 3 elements, first 4 elements, first 5 elements , on.

here's code:

import java.io.*; import java.util.arrays; public class monkmulti {     public static void main(string args[] ) throws ioexception {          bufferedreader br = new bufferedreader(new inputstreamreader(system.in));         int n = integer.parseint(br.readline());    // no. of elements         string xs = br.readline(); //accepting elements in string         xs=xs+" ";         if(n<1||n>100000)  //constraint             system.exit(0);         int i,temp,count=0;         for(i=0;i<xs.length();i++)         {             if(xs.charat(i)==' ')             {                 count++;             }         }         if(count!=n)    //checks if no. of elements equal n             system.exit(0);         int[] x=new int[count];         int k=0;         temp=0;         for(i=0;i<xs.length();i++)         {             if(xs.charat(i)==' ')             {                 x[k++]=integer.parseint(xs.substring(temp, i));                 temp=i+1;             }         }         count=0;         int len=x.length,j;         int[] x1=new int[len];         system.arraycopy(x, 0, x1, 0, len);         for(i=0;i<len;i++)         {             if(x[i]<1||x[i]>100000)      //constraint each element                 system.exit(0);         }         int m1=0,m2=0,m3=0;         int max1=x[0],max2=x[0],max3=x[0];         /*code improved below here*/         for(i=2;i<len;i++)                     {             for(j=0;j<=i;j++)             {                 for(k=0;k<i;k++)                 {                     if(x1[k]>x1[k+1])                     {                         temp=x1[k];                         x1[k]=x1[k+1];                         x1[k+1]=temp;                     }                 }             }             system.out.println(x1[i]*x1[i-1]*x1[i-2]);         }     } } 

input:

n=user inputs no. of elements in array
xs= string accepting n elements separated space

output:

product considering first 3 elements
product considering first 4 elements
on..

example:

input:
5
6 2 9 3 8

output:
-1
-1
108
162
432

explanation there 5 integers 6,2,9,3,8
third index, top 3 numbers 6,2 , 9 product 108.
fourth index, top 3 numbers 6,9 , 3 product 162.
fifth index, top 3 numbers 6,9 , 8 product 432.

if understand, need this:

the order o(items * log(subgroups)) -> o(items * log(3)) -> o(items)

public static void product(int[] items, int subgroup) {     if (subgroup > 0 && items.length >= subgroup) {         // save largest numbers:         priorityqueue<integer> maxelements = new priorityqueue<>(subgroup);         int product = 1;         (int = 0; < items.length; i++) {             // queue of largest numbers full:             if (maxelements.size() == subgroup) {                 // minimum of previous largest number lower new number                 if (maxelements.peek() < items[i]) {                     // swapping                     product /= maxelements.poll();                     product *= items[i];                     maxelements.add(items[i]);                 }                 system.out.println(product);             } else {                 product *= items[i];                 maxelements.add(items[i]);                 if (maxelements.size() < subgroup) {                     //the queue of largest numbers isn't full                     system.out.println("-1");                 } else {                     // queue of largest numbers full                     system.out.println(product);                 }             }         }     } }  public static void main(string[] args) {     int[] input = {6, 2, 9, 3, 8};     product(input, 3); } 

output:

-1 -1 108 162 432 

edit: little bit faster:

private static void heap(int[] maxelements) {     int candidate = 1;     if (maxelements[1] > maxelements[2]) {         candidate = 2;     }     if (maxelements[0] > maxelements[candidate]) {         int temp = maxelements[0];         maxelements[0] = maxelements[candidate];         maxelements[candidate] = temp;     } }  private static int addelement(int k, int[] maxelements, int item) {     if (k < 3) {         maxelements[k++] = item;         if (k < 3) {             system.out.println("-1");         } else {             heap(maxelements);             system.out.println(maxelements[0] * maxelements[1] * maxelements[2]);         }     } else {         if (maxelements[0] < item) {             maxelements[0] = item;             heap(maxelements);         }         system.out.println(maxelements[0] * maxelements[1] * maxelements[2]);     }     return k; }  public static void main(string args[]) throws ioexception {      bufferedreader br = new bufferedreader(new inputstreamreader(system.in));     int n = integer.parseint(br.readline());    // no. of elements     string line = br.readline(); //accepting elements in string     int[] maxelements = new int[3];     int k = 0;     int item = 0;     char c;     (int = 0; < line.length(); i++) {         c = line.charat(i);         if (c == ' ') {             k = addelement(k, maxelements, item);             item = 0;         } else {             item = item * 10 + (c - '0');         }     }     addelement(k, maxelements, item); }