Java运行时间计算

Question

我有两个不同的程序，正在计算使用纳秒时间方法的运行时间。 由于第一个代码是线性代码块，因此很容易弄清楚。 在代码的开头，我把这一行：

long startTime = System.nanoTime();

在代码末尾，我把这一行：

long estimatedTime = System.nanoTime() - startTime;
System.out.println(estimatedTime);

但是，我的第二个程序有两个类文件。（请参见下文）应在哪里插入两段代码以最佳地计算运行时间？ 是每个班级还是一个班级？ 谢谢！

import java.util.Random;

public class LinearArray {
    private int[] data;    // array of values
    private static Random generator = new Random();

    // Create an array of a given size and fill it with random numbers
    public LinearArray(int size) {
        data = new int[size];  // Create space for the array

        // fill the array with random ints in the range 10 – 99
        for (int i = 0; i < size; i++)
            data[i] = 10 + generator.nextInt(90);
    } //end of the LinearArray constructor

    // Perform a linear search on the data set
    public int linearSearch(int searchKey) {
        //Search through the array sequentially
        for (int index = 0; index < data.length; index++)
            if (data[index] == searchKey)
                return index;   // Return the index of the integer
        return -1;  // the integer was not found
    }  // end of the method linearSearch

    // a method to output the values in the array
    public String toString() {
        StringBuilder temporary = new StringBuilder();

        // iterate through the array
        for (int element : data)
            temporary.append(element + "  ");
        temporary.append("\n");
        return temporary.toString();
    }
} // end of the class LinearArray

import java.util.Scanner;

public class LinearSearchTest {
    public static void main(String args[]) {
        // Create Scanner object to input data
        Scanner input = new Scanner(System.in);

        int searchInt;   // the search key
        int position;    //  Location of the search key in the array

        // Create and then output the array
        LinearArray searchArray = new LinearArray(10);
        System.out.println(searchArray);  //print the array

        // get the input from the user
        System.out.print("Please enter an integer value (enter -1 to quit):   ");
        searchInt = input.nextInt();   // read the first integer value from the user

        // repeatedly input an integer; input -1 to terminate the program
        while (searchInt != -1) {
            // perform the linear search
            position = searchArray.linearSearch(searchInt);

            if (position == -1) ///the integer was not found
                System.out.println("The integer " + searchInt + "  was not found. \n");
            else   // the integer was found
                System.out.println("The integer  " + searchInt + " was found at position  " +
                        position + ".\n");

            // get the input from the user
            System.out.print("Please enter an integer value (enter -1 to quit): ");
            searchInt = input.nextInt();  // this reads the next input from the user
        }  // end while
    }  // end the main method
}  // end the class LinearSearchTest

Answer 1

1. 在while (searchInt != -1)之前LinearSearchTest

2. 采取差异关闭后while (searchInt != -1)的LinearSearchTest

Answer 2

Checek在哪里是您的静态void主要函数，它将在运行您的应用程序时首先运行。 将您的代码放在该函数中。 每次运行应用程序时，都将从该功能开始。

Answer 3

要检查整个代码的运行时，请在主方法的开始处将“开始时间”放在

Scanner input = new Scanner ( System.in );

或者，如果您只想检查搜索零件的运行时间，请将“开始时间”放在while循环之前。

-'estimatedTime'在//结束后

Answer 4

测量程序等待用户输入的时间毫无意义。

并且，在大小为10的数组中进行线性搜索不会返回有意义的值。

您想通过测量此类程序的时间来实现什么？

如果要比较线性搜索算法，请设置大量自动执行的测试运行，并使用随机数来搜索和计时这批执行的执行时间，然后除以次数...