Java 测量执行时间的代码出现问题_Java_Sorting_Time_Execution Time

Java 测量执行时间的代码出现问题

java sorting time

Java 测量执行时间的代码出现问题,java,sorting,time,execution-time,Java,Sorting,Time,Execution Time,因此，我试图测量一些排序方法的执行时间这是我的密码： public static void main(String[] args) { ... MeasureExecutionTime(new Runnable() { public void run() { insertionSort(C); } }, "insertionSort()"); } ===================== private static void MeasureExecutionTime(R

因此，我试图测量一些排序方法的执行时间

这是我的密码：

public static void main(String[] args)
{
    ...

    MeasureExecutionTime(new Runnable() { public void run() { insertionSort(C); } }, "insertionSort()");
}

=====================

private static void MeasureExecutionTime(Runnable r, String s)
{
    startTime = System.nanoTime();
    try
    {
        r.run();
    }
    finally
    {
        endTime = System.nanoTime();
    }
    elapsedTime = endTime - startTime;
    System.out.println(s + " takes " + elapsedTime + " nano-seconds which is " + formatTime(elapsedTime));
}

public static String formatTime(long nanoSeconds)
{
    long hours, minutes, remainder, totalSecondsNoFraction;
    double totalSeconds, seconds;

    totalSeconds = (double) nanoSeconds / 1000000000.0;
    String s = Double.toString(totalSeconds);
    String [] arr = s.split("\\.");
    totalSecondsNoFraction = Integer.parseInt(arr[0]);
    hours = totalSecondsNoFraction / 3600;
    remainder = totalSecondsNoFraction % 3600;
    minutes = remainder / 60;
    seconds = remainder % 60;
    seconds = Double.parseDouble(Long.toString((long)seconds) + Double.parseDouble("." + arr[1]));

    StringBuilder result = new StringBuilder(".");
    String sep = "", nextSep = " and ";
    if(seconds > 0)
    {
        if(seconds > 1) result.insert(0, " seconds").insert(0, seconds);
        else result.insert(0, " second").insert(0, seconds);
        sep = nextSep;
        nextSep = ", ";
    }
    if(minutes > 0)
    {
        if(minutes > 1) result.insert(0, sep).insert(0, " minutes").insert(0, minutes);
        else result.insert(0, sep).insert(0, " minute").insert(0, minutes);
        sep = nextSep;
        nextSep = ", ";
    }
    if(hours > 0)
    {
        if(hours > 1) result.insert(0, sep).insert(0, " hours").insert(0, hours);
        else result.insert(0, sep).insert(0, " hour").insert(0, hours);
    }
    return result.toString();
}

=====================

private static void MeasureExecutionTime(Runnable r, String s)
{
    startTime = System.nanoTime();
    try
    {
        r.run();
    }
    finally
    {
        endTime = System.nanoTime();
    }
    elapsedTime = endTime - startTime;
    System.out.println(s + " takes " + elapsedTime + " nano-seconds which is " + formatTime(elapsedTime));
}

public static String formatTime(long nanoSeconds)
{
    long hours, minutes, remainder, totalSecondsNoFraction;
    double totalSeconds, seconds;

    totalSeconds = (double) nanoSeconds / 1000000000.0;
    String s = Double.toString(totalSeconds);
    String [] arr = s.split("\\.");
    totalSecondsNoFraction = Integer.parseInt(arr[0]);
    hours = totalSecondsNoFraction / 3600;
    remainder = totalSecondsNoFraction % 3600;
    minutes = remainder / 60;
    seconds = remainder % 60;
    seconds = Double.parseDouble(Long.toString((long)seconds) + Double.parseDouble("." + arr[1]));

    StringBuilder result = new StringBuilder(".");
    String sep = "", nextSep = " and ";
    if(seconds > 0)
    {
        if(seconds > 1) result.insert(0, " seconds").insert(0, seconds);
        else result.insert(0, " second").insert(0, seconds);
        sep = nextSep;
        nextSep = ", ";
    }
    if(minutes > 0)
    {
        if(minutes > 1) result.insert(0, sep).insert(0, " minutes").insert(0, minutes);
        else result.insert(0, sep).insert(0, " minute").insert(0, minutes);
        sep = nextSep;
        nextSep = ", ";
    }
    if(hours > 0)
    {
        if(hours > 1) result.insert(0, sep).insert(0, " hours").insert(0, hours);
        else result.insert(0, sep).insert(0, " hour").insert(0, hours);
    }
    return result.toString();
}

我的问题是：

运行此程序后，我输入

int[1000000]

作为输入，它在大约12-13分钟内执行

insertionSort（）

，然后返回：

insertionSort() takes 767186856920 nano-seconds which is 12 minutes and 470.18685692 seconds.

为什么会有470秒？我的代码有什么问题

=========================

private static void MeasureExecutionTime(Runnable r, String s)
{
    startTime = System.nanoTime();
    try
    {
        r.run();
    }
    finally
    {
        endTime = System.nanoTime();
    }
    elapsedTime = endTime - startTime;
    System.out.println(s + " takes " + elapsedTime + " nano-seconds which is " + formatTime(elapsedTime));
}

public static String formatTime(long nanoSeconds)
{
    long hours, minutes, remainder, totalSecondsNoFraction;
    double totalSeconds, seconds;

    totalSeconds = (double) nanoSeconds / 1000000000.0;
    String s = Double.toString(totalSeconds);
    String [] arr = s.split("\\.");
    totalSecondsNoFraction = Integer.parseInt(arr[0]);
    hours = totalSecondsNoFraction / 3600;
    remainder = totalSecondsNoFraction % 3600;
    minutes = remainder / 60;
    seconds = remainder % 60;
    seconds = Double.parseDouble(Long.toString((long)seconds) + Double.parseDouble("." + arr[1]));

    StringBuilder result = new StringBuilder(".");
    String sep = "", nextSep = " and ";
    if(seconds > 0)
    {
        if(seconds > 1) result.insert(0, " seconds").insert(0, seconds);
        else result.insert(0, " second").insert(0, seconds);
        sep = nextSep;
        nextSep = ", ";
    }
    if(minutes > 0)
    {
        if(minutes > 1) result.insert(0, sep).insert(0, " minutes").insert(0, minutes);
        else result.insert(0, sep).insert(0, " minute").insert(0, minutes);
        sep = nextSep;
        nextSep = ", ";
    }
    if(hours > 0)
    {
        if(hours > 1) result.insert(0, sep).insert(0, " hours").insert(0, hours);
        else result.insert(0, sep).insert(0, " hour").insert(0, hours);
    }
    return result.toString();
}

编辑：

替换

seconds=Double.parseDouble（Long.toString（（Long）seconds）+Double.parseDouble（“.”+arr[1]）后带seconds=seconds+Double.parseDouble（“.”+arr[1]），上一期已消失，但出现另一期：
insertionSort() takes 22864 nano-seconds which is 2.000002864 seconds.

它应该是0.000022864秒。

=========================
private static void MeasureExecutionTime(Runnable r, String s)
{
    startTime = System.nanoTime();
    try
    {
        r.run();
    }
    finally
    {
        endTime = System.nanoTime();
    }
    elapsedTime = endTime - startTime;
    System.out.println(s + " takes " + elapsedTime + " nano-seconds which is " + formatTime(elapsedTime));
}

public static String formatTime(long nanoSeconds)
{
    long hours, minutes, remainder, totalSecondsNoFraction;
    double totalSeconds, seconds;

    totalSeconds = (double) nanoSeconds / 1000000000.0;
    String s = Double.toString(totalSeconds);
    String [] arr = s.split("\\.");
    totalSecondsNoFraction = Integer.parseInt(arr[0]);
    hours = totalSecondsNoFraction / 3600;
    remainder = totalSecondsNoFraction % 3600;
    minutes = remainder / 60;
    seconds = remainder % 60;
    seconds = Double.parseDouble(Long.toString((long)seconds) + Double.parseDouble("." + arr[1]));

    StringBuilder result = new StringBuilder(".");
    String sep = "", nextSep = " and ";
    if(seconds > 0)
    {
        if(seconds > 1) result.insert(0, " seconds").insert(0, seconds);
        else result.insert(0, " second").insert(0, seconds);
        sep = nextSep;
        nextSep = ", ";
    }
    if(minutes > 0)
    {
        if(minutes > 1) result.insert(0, sep).insert(0, " minutes").insert(0, minutes);
        else result.insert(0, sep).insert(0, " minute").insert(0, minutes);
        sep = nextSep;
        nextSep = ", ";
    }
    if(hours > 0)
    {
        if(hours > 1) result.insert(0, sep).insert(0, " hours").insert(0, hours);
        else result.insert(0, sep).insert(0, " hour").insert(0, hours);
    }
    return result.toString();
}

EDIT2:
我可能会发现错误。当nanoSeconds
较大时，arr[1]
将正常，但当nanoSeconds
较小时，arr[1]
将转换为指数形式，即14931纳秒=>4.931E-6秒。
。我如何解决这个问题
==========================
private static void MeasureExecutionTime(Runnable r, String s)
{
    startTime = System.nanoTime();
    try
    {
        r.run();
    }
    finally
    {
        endTime = System.nanoTime();
    }
    elapsedTime = endTime - startTime;
    System.out.println(s + " takes " + elapsedTime + " nano-seconds which is " + formatTime(elapsedTime));
}

public static String formatTime(long nanoSeconds)
{
    long hours, minutes, remainder, totalSecondsNoFraction;
    double totalSeconds, seconds;

    totalSeconds = (double) nanoSeconds / 1000000000.0;
    String s = Double.toString(totalSeconds);
    String [] arr = s.split("\\.");
    totalSecondsNoFraction = Integer.parseInt(arr[0]);
    hours = totalSecondsNoFraction / 3600;
    remainder = totalSecondsNoFraction % 3600;
    minutes = remainder / 60;
    seconds = remainder % 60;
    seconds = Double.parseDouble(Long.toString((long)seconds) + Double.parseDouble("." + arr[1]));

    StringBuilder result = new StringBuilder(".");
    String sep = "", nextSep = " and ";
    if(seconds > 0)
    {
        if(seconds > 1) result.insert(0, " seconds").insert(0, seconds);
        else result.insert(0, " second").insert(0, seconds);
        sep = nextSep;
        nextSep = ", ";
    }
    if(minutes > 0)
    {
        if(minutes > 1) result.insert(0, sep).insert(0, " minutes").insert(0, minutes);
        else result.insert(0, sep).insert(0, " minute").insert(0, minutes);
        sep = nextSep;
        nextSep = ", ";
    }
    if(hours > 0)
    {
        if(hours > 1) result.insert(0, sep).insert(0, " hours").insert(0, hours);
        else result.insert(0, sep).insert(0, " hour").insert(0, hours);
    }
    return result.toString();
}

EDIT3:
好的，我找到了解决方案：
if(arr[1].contains("E")) seconds = Double.parseDouble("." + arr[1]);
else seconds += Double.parseDouble("." + arr[1]);

问题在于：
seconds = Double.parseDouble(Long.toString((long)seconds) + 
                             Double.parseDouble("0." + arr[1]));

假设seconds
是12
进入此行，而arr[1]
是“456”
。然后
seconds = Double.parseDouble("12" + Double.parseDouble("0.456"));
seconds = Double.parseDouble("12" + 0.456);
seconds = Double.parseDouble("12" + "0.456");
seconds = Double.parseDouble("120.456");
seconds = 120.456.

为什么不干脆做：
seconds = seconds + Double.parseDouble("0." + arr[1]);

问题在于：
seconds = Double.parseDouble(Long.toString((long)seconds) + 
                             Double.parseDouble("0." + arr[1]));

假设seconds
是12
进入此行，而arr[1]
是“456”
。然后
seconds = Double.parseDouble("12" + Double.parseDouble("0.456"));
seconds = Double.parseDouble("12" + 0.456);
seconds = Double.parseDouble("12" + "0.456");
seconds = Double.parseDouble("120.456");
seconds = 120.456.

为什么不干脆做：
seconds = seconds + Double.parseDouble("0." + arr[1]);

我认为您正在连接两个字符串“47”和“0.186…”。
我认为您正在连接两个字符串“47”和“0.186…”。
问题是这行：
seconds = Double.parseDouble(Long.toString((long)seconds) + Double.parseDouble("0." + arr[1]));

第二个parseDouble
返回“0.18685692”。由于arr[1]
已经是小数点右侧的字符串，只需使用：
seconds = Double.parseDouble(Long.toString((long)seconds) + "." + arr[1]);

问题在于这一行：
seconds = Double.parseDouble(Long.toString((long)seconds) + Double.parseDouble("0." + arr[1]));

第二个parseDouble
返回“0.18685692”。由于arr[1]
已经是小数点右侧的字符串，只需使用：
seconds = Double.parseDouble(Long.toString((long)seconds) + "." + arr[1]);

连接字符串时，将添加一个额外的零。为了避免这种问题，最好使用格式化程序来创建字符串。请参见此处的详细信息
此外，手工计算正确答案总是有帮助的。这使得问题更容易找到。
在连接字符串时，您添加了一个额外的零。为了避免这种问题，最好使用格式化程序来创建字符串。请参见此处的详细信息
此外，手工计算正确答案总是有帮助的。这使得问题更容易找到。
抱歉，出现了另一个问题，我不得不取消选择此作为答案抱歉，出现了另一个问题，我不得不取消选择此作为答案