Java linear bucket sort

public class MyTimer {
    private static long begin;

    public static void time_start(){
        begin = System.nanoTime();
    }

    public static double time_end_milli_seconds(){
        return System.nanoTime()-begin/1e6;

    }

    public static double time_end_seconds(){
        double total_time =  (System.nanoTime()-begin)/1e6;
        return ((double)((int)total_time))/1000;

    }

}

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class RandomGenerator {

    public int[] random_generate(int min,int max,int numtrials){

        int[] int_array = new int[numtrials];

        Random random = new Random();

        for (int i = 0; i < numtrials; i++) {
            int random_num = random.nextInt(max)%(max-min+1) + min;
            int_array[i] = random_num;
        }

        return int_array;
    }

}

import java.util.ArrayList;
import java.util.List;

public class BucketSort {

    public int[] bucket_sort(int[] original_array,int max){

            // index: 0-99 but max is : 100 . the point is the array index for bucketsort
           int[] store_array = new int[max+1];

            for (int i = 0; i < original_array.length; i++) {
                int int_num = original_array[i];

                // here is the miracle of bucketsort
                store_array[int_num]= ++store_array[int_num];
            }

           int[] final_sorted_array = new int[original_array.length];
           int cherry_pointer = 0;

        for (int cherry = 0; cherry < store_array.length; cherry++) {

            int cherry_num = store_array[cherry];
            for (int j = 0; j < cherry_num; j++) {
                final_sorted_array[cherry_pointer]=cherry;
                ++cherry_pointer;
            }

        }

           return final_sorted_array;
    }
}

public class TestBucketSort {

    public double test_bucketsort(){

        MyTimer.time_start();
        int min = 1;
        int max = 300;
        int num_trails = 10000;

        BucketSort bucketSort = new BucketSort();
        RandomGenerator randomGenerator = new RandomGenerator();

        int[] random_array = randomGenerator.random_generate(min,max,num_trails);

        for (int i = num_trails-100; i < random_array.length; i++) {
            System.out.println(random_array[i]);
        }

        int[] sorted_array = bucketSort.bucket_sort(random_array,max);

        double time_end = MyTimer.time_end_seconds();

      for (int i = 0; i < sorted_array.length; i++) {
            System.out.println(sorted_array[i]);
        }

        System.out.println("Time elapse : "+time_end+"s   sorted_array.length: "+sorted_array.length);

        return time_end;
    }

    public static void main(String[] args) {

        TestBucketSort testBucketSort = new TestBucketSort();
        testBucketSort.test_bucketsort();

    }
}