Sort an array of 0's 1's 2's, Java

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//'main' method must be in a class 'Rextester'.
//openjdk version '11.0.5' 
import java.io.*;
import java.util.*;
import java.lang.*;

class Rextester
{  
    public static void main(String args[]) throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            int n = Integer.parseInt(br.readLine());
            int[] arr = new int[n];
            
            StringTokenizer st = new StringTokenizer(br.readLine());
            for(int i=0;i<n;i++){
                //if(st.hasMoreToken())
                  arr[i] = Integer.parseInt(st.nextToken());
            }
        int one=0;
        int two=0;
        int zero=0;
        for(int i=0;i<arr.length;i++){
            if(arr[i]==0)
                zero++;
            else if(arr[i]==1)
                one++;
            else if(arr[i]==2)
                two++;
        }
        int index=0;
        while(zero-->0){
            arr[index]=0;
            index++;
        }
        while(one-->0){
            arr[index]=1;
            index++;
        }
        while(two-->0){
            arr[index]=2;
            index++;
        }
        for(int var:arr)
            System.out.print(var+" ");
        
        
        
    }
}

[ - ] Show input
Compilation time: 1.33 sec, absolute running time: 0.35 sec, cpu time: 0.27 sec, memory peak: 38 Mb, absolute service time: 1,86 sec