Java 排序代码和运行时间

所以我有这两个代码。其中一个叫做MyTimer和SortCode。MyTimer计算一段代码的运行时间，SortCode读取一个文件并打印出排序后的代码。如何使用MyTimer查找每个排序代码的运行时间

import java.io.*;
import java.util.*;


public class SortCode
{
    public static void main(String[] args)
    {
        ArrayList<Integer> hold = new ArrayList<Integer>();
        try(
              //Open files
              FileReader reader = new FileReader("TestData.txt");
              Scanner in = new Scanner(reader);
              FileWriter writer = new FileWriter("SortedData.txt");
              PrintWriter out = new PrintWriter(writer);
           )
        {
            while(in.hasNextLine())
            {
                String next = in.nextLine();
                try
                {
                    int n = Integer.parseInt(next);
                    hold.add(n);
                }
                catch(NumberFormatException e)
                {
                    System.out.println("Invalid input " + next);
                }
            }

            insertionSort(hold);
            for(Integer i : hold)
               out.printf("%7d\n", i);
        }
        catch(IOException e)
        {
            System.out.println("Error opening the files." + e);
            System.exit(1);
        }

    }

  public static <T extends Comparable<T>>
  void selectionSort(List<T> table)
  {
     int size = table.size();
     for(int i = 0; i < size - 1; i++)
     {
        int minPos = i;
        T minValue = table.get(i);
        for(int k = i + 1; k < size; k++)
        {
           T nextValue = table.get(k);
           if( nextValue.compareTo(minValue) < 0)
           {
               minPos = k;
               minValue = nextValue;
           }
        }
        if(minPos != i)
        {
           T temp = table.get(i);
           table.set(minPos,temp);
           table.set(i, minValue);
        }
     }
  }


    public static <T extends Comparable<T>>
    int binSearch(ArrayList<T> table, int low, int high, T value)
    {
        while(low <= high)
        {
            int mid = (low + high)/2;
            int result = value.compareTo(table.get(mid));
            if(result  == 0)
              return mid;
            if(result < 0)
              high = mid - 1;
            else low = mid + 1;
        }
        return -low -1;
    }

    public static <T extends Comparable<T>>
    void insertionSort(ArrayList<T> table)
    {
      int size = table.size();
      for(int i = 1; i < size; i++)
      {
         T temp = table.remove(i);
         int pos = binSearch(table, 0, i - 1, temp);
         if(pos < 0)
           pos = -pos - 1;
         table.add(pos, temp);

      }
    }

    public static <T extends Comparable<T>>
    void mergeSort(List<T> table)
    {
      int size = table.size();
      if(size <= 1)
         return;

      int size1 = size/2;
      int size2 = size - size1;
      List<T> v1 = new ArrayList<T>();
      List<T> v2 = new ArrayList<T>();

      for(int i = 0; i < size1; i++)
         v1.add(table.get(i));
      for(int i = 0; i < size2; i++)
         v2.add(table.get(size1 + i));

      mergeSort(v1);
      mergeSort(v2);

      int i1 = 0, i2 = 0;
      int i = 0;
      T value1 = v1.get(i1);
      T value2 = v2.get(i2);

      while(i1 < size1 && i2 < size2)
      {
        if(value1.compareTo(value2) <= 0)
        {
           table.set(i++, value1);
           i1++;
           if(i1 < size1)
             value1 = v1.get(i1);
        }
        else
        {
           table.set(i++, value2);
           i2++;
           if(i2 < size2)
               value2 = v2.get(i2);
        }
      }
      int k;
      if(i1 < size1)
      {
         for(k = i1; k < size1; k++)
            table.set(i++, v1.get(k));
      }
      else
      {
         for(k = i2; k < size2; k++)
           table.set(i++, v2.get(k));
      }
    }

}

---

你可以这样使用它

MyTimer() timer = new MyTimer(); // create new MyTimer instance 
timer.start(); // start the timer
insertionSort(hold); // run the sorting code here
timer.stop(); // stop the timer
long elapsedTime = timer.getElapsedTime(); // get the elapsed time

---

文件阅读器和Writer@Dem完全一样。创建一个

MyTimer

实例，并在要检查的每个代码之前和之后调用

start（）

和

stop（）

。如何打印它？它不会打印。@Dem什么东西不会打印？经过的时间也是为什么要将纳秒更改为毫秒？

MyTimer() timer = new MyTimer(); // create new MyTimer instance 
timer.start(); // start the timer
insertionSort(hold); // run the sorting code here
timer.stop(); // stop the timer
long elapsedTime = timer.getElapsedTime(); // get the elapsed time