Two different functions to create histogram are compared on speed

Histogram.java

import java.util.Random;

public class Histogram {
	static int NUM_STUDENTS = 20000;
	static int HIGHEST_GRADE = 10;

	//Function to compute histogram faster O(N)
	public void getHistFast(int iArr[], int oArr[])
	{
		for(int i=0;i<iArr.length;i++)
		{	
			oArr[iArr[i]]++;
		}
	}

	//Function to compute histogram faster O(N^3)
	public void getHistSlow(int iArr[], int oArr[])
	{
		for(int i=0;i<HIGHEST_GRADE;i++)
		{
			int count=0;
			for(int j=0;j<iArr.length;j++)
			{
				if(iArr[j]==i)
				{
					count++;
				}
			}
			oArr[i]=count;
		}
	}

	public static void main(String[] args)
	{
		Random random 				      = new Random();
		int[] student_grades 		    = random.ints(NUM_STUDENTS, 0,HIGHEST_GRADE).toArray();
		int[] grade_histogram 		  = new int[HIGHEST_GRADE];
		int[] grade_histogram_fast 	= new int[HIGHEST_GRADE];

		Histogram histObj           = new Histogram();
		long start                  = System.currentTimeMillis(); //Count Time
		histObj.getHistSlow(student_grades, grade_histogram);
		long endSlow                = System.currentTimeMillis(); 
		histObj.getHistFast(student_grades, grade_histogram_fast);
		long endFast                = System.currentTimeMillis(); 

		System.out.println("Time Taken For Slow Hist: "+ (endSlow - start) + " ms");
		System.out.println("Time Taken For Fast Hist: "+ (endFast - endSlow) + " ms");

	}
}