gettendency.java

The running time of quicksort can be improved in practice by taking advantage of the fast running t

import javax.swing.JOptionPane;

public class GetTendency
{
	public static void main(String[] args) 
	{
		//Input the length of the array.
		String strLengthOfArray = JOptionPane.showInputDialog(null, "Enter the length of the array:", "Input", JOptionPane.QUESTION_MESSAGE);
		int lengthOfArray = 0;
		try
		{
			lengthOfArray = Integer.parseInt(strLengthOfArray);
		}
		catch (Exception e)
		{
			JOptionPane.showMessageDialog(null, "Please enter an integer!", "Error", JOptionPane.WARNING_MESSAGE);
			System.exit(0);
		}

		long timeSpentByInsertionSort = 0;
		long timeSpentByQuickSort = 0;
		
		//Do the experiments one million times in order to reduce the coincidence.
		for (int k = 1; k <= 1000000; k ++)
		{
			//Create the sorce arrays.
			double[] sourceArrayForInsertionSort = new double[lengthOfArray];
			double[] sourceArrayForQuickSort = new double[lengthOfArray];
			for (int n = 0; n < sourceArrayForInsertionSort.length; n ++)
				sourceArrayForInsertionSort[n] = Math.random();
			for (int n = 0; n < sourceArrayForQuickSort.length; n ++)
				sourceArrayForQuickSort[n] = sourceArrayForInsertionSort[n];

			//Register the time spent by insertion sort.
			Sort insertionSort = new Sort(sourceArrayForInsertionSort);
			long startTimeOfInsertionSort = System.nanoTime();
			insertionSort.insertionSort(0, sourceArrayForInsertionSort.length - 1);
			timeSpentByInsertionSort += System.nanoTime() - startTimeOfInsertionSort;

			//Register the time spent by quick sort.
			Sort quickSort = new Sort(sourceArrayForQuickSort);
			long startTimeOfQuickSort = System.nanoTime();
			quickSort.quickSort(0, sourceArrayForQuickSort.length - 1);
			timeSpentByQuickSort += System.nanoTime() - startTimeOfQuickSort;
		}

		//Output the result.
		System.out.println("The length of the array is: " + lengthOfArray);
		System.out.println("The average nanoseconds spent by insertion sort is: " + (timeSpentByInsertionSort / 1000000));
		System.out.println("The average nanoseconds spent by quick sort is: " + (timeSpentByQuickSort / 1000000));
	}
}