我想要这样的东西:
public class Stream
{
public startTime;
public endTime;
public getDuration()
{
return startTime - endTime;
}
}
同样重要的是，例如，如果startTime是23:00,endTime是1:00，则持续时间为2:00。
为了在Java中实现这一点，应该使用哪些类型?
当前回答
我发现这段代码在计时时很有用:
public class Et {
public Et() {
reset();
}
public void reset() {
t0=System.nanoTime();
}
public long t0() {
return t0;
}
public long dt() {
return System.nanoTime()-t0();
}
public double etms() {
return etms(dt());
}
@Override public String toString() {
return etms()+" ms.";
}
public static double etms(long dt) {
return dt/1000000.; // 1_000_000. breaks cobertura
}
private Long t0;
}
其他回答
用这个:
SimpleDateFormat format = new SimpleDateFormat("HH:mm");
Date d1 = format.parse(strStartTime);
Date d2 = format.parse(strEndTime);
long diff = d2.getTime() - d1.getTime();
long diffSeconds,diffMinutes,diffHours;
if (diff > 0) {
diffSeconds = diff / 1000 % 60;
diffMinutes = diff / (60 * 1000) % 60;
diffHours = diff / (60 * 60 * 1000);
}
else{
long diffpos = (24*((60 * 60 * 1000))) + diff;
diffSeconds = diffpos / 1000 % 60;
diffMinutes = diffpos / (60 * 1000) % 60;
diffHours = (diffpos / (60 * 60 * 1000));
}
(同样重要的是，例如，如果startTime是23:00,endTime是1:00，则持续时间为2:00。)
“else”部分可以得到正确的答案
如果您从System.currentTimeMillis()获取时间戳，那么您的时间变量应该是长变量。
不幸的是，目前发布的十个答案中没有一个是完全正确的。
如果您正在测量经过的时间，并且希望它是正确的，那么必须使用System.nanoTime()。您不能使用System.currentTimeMillis()，除非您不介意结果是错误的。
The purpose of nanoTime is to measure elapsed time, and the purpose of currentTimeMillis is to measure wall-clock time. You can't use the one for the other purpose. The reason is that no computer's clock is perfect; it always drifts and occasionally needs to be corrected. This correction might either happen manually, or in the case of most machines, there's a process that runs and continually issues small corrections to the system clock ("wall clock"). These tend to happen often. Another such correction happens whenever there is a leap second.
由于nanoTime的目的是测量经过的时间，因此它不受任何这些小修正的影响。它是你想要使用的。当前使用currentTimeMillis进行的任何计时都将关闭——甚至可能为负值。
您可能会说，“这听起来似乎并没有那么重要”，对此我说，也许不是，但总的来说，正确的代码不就是比错误的代码好吗?此外，nanoTime打字时间更短。
之前发布的关于nanoTime通常只有微秒精度的免责声明是有效的。此外，它可能需要超过一微秒的时间来调用，这取决于环境(另一个也是如此)，所以不要期望对非常非常小的间隔进行正确的计时。
我发现这段代码在计时时很有用:
public class Et {
public Et() {
reset();
}
public void reset() {
t0=System.nanoTime();
}
public long t0() {
return t0;
}
public long dt() {
return System.nanoTime()-t0();
}
public double etms() {
return etms(dt());
}
@Override public String toString() {
return etms()+" ms.";
}
public static double etms(long dt) {
return dt/1000000.; // 1_000_000. breaks cobertura
}
private Long t0;
}
Byte Stream Reader Elapsed Time for 23.7 MB is 96 secs
import java.io.*;
import java.io.IOException;
import java.util.Scanner;
class ElaspedTimetoCopyAFileUsingByteStream
{
private long startTime = 0;
private long stopTime = 0;
private boolean running = false;
public void start()
{
this.startTime = System.currentTimeMillis();
this.running = true;
}
public void stop()
{
this.stopTime = System.currentTimeMillis();
this.running = false;
}
public long getElapsedTime()
{
long elapsed;
if (running) {
elapsed = (System.currentTimeMillis() - startTime);
}
else {
elapsed = (stopTime - startTime);
}
return elapsed;
}
public long getElapsedTimeSecs()
{
long elapsed;
if (running)
{
elapsed = ((System.currentTimeMillis() - startTime) / 1000);
}
else
{
elapsed = ((stopTime - startTime) / 1000);
}
return elapsed;
}
public static void main(String[] args) throws IOException
{
ElaspedTimetoCopyAFileUsingByteStream s = new ElaspedTimetoCopyAFileUsingByteStream();
s.start();
FileInputStream in = null;
FileOutputStream out = null;
try {
in = new FileInputStream("vowels.txt"); // 23.7 MB File
out = new FileOutputStream("output.txt");
int c;
while ((c = in.read()) != -1) {
out.write(c);
}
}finally {
if (in != null) {
in.close();
}
if (out != null) {
out.close();
}
}
s.stop();
System.out.println("elapsed time in seconds: " + s.getElapsedTimeSecs());
}
}
[Elapsed Time for Byte Stream Reader][1]
**Character Stream Reader Elapsed Time for 23.7 MB is 3 secs**
import java.io.*;
import java.io.IOException;
import java.util.Scanner;
class ElaspedTimetoCopyAFileUsingCharacterStream
{
private long startTime = 0;
private long stopTime = 0;
private boolean running = false;
public void start()
{
this.startTime = System.currentTimeMillis();
this.running = true;
}
public void stop()
{
this.stopTime = System.currentTimeMillis();
this.running = false;
}
public long getElapsedTime()
{
long elapsed;
if (running) {
elapsed = (System.currentTimeMillis() - startTime);
}
else {
elapsed = (stopTime - startTime);
}
return elapsed;
}
public long getElapsedTimeSecs()
{
long elapsed;
if (running)
{
elapsed = ((System.currentTimeMillis() - startTime) / 1000);
}
else
{
elapsed = ((stopTime - startTime) / 1000);
}
return elapsed;
}
public static void main(String[] args) throws IOException
{
ElaspedTimetoCopyAFileUsingCharacterStream s = new ElaspedTimetoCopyAFileUsingCharacterStream();
s.start();
FileReader in = null; // CharacterStream Reader
FileWriter out = null;
try {
in = new FileReader("vowels.txt"); // 23.7 MB
out = new FileWriter("output.txt");
int c;
while ((c = in.read()) != -1) {
out.write(c);
}
}finally {
if (in != null) {
in.close();
}
if (out != null) {
out.close();
}
}
s.stop();
System.out.println("elapsed time in seconds: " + s.getElapsedTimeSecs());
}
}
[Elapsed Time for Character Stream Reader][2]
[1]: https://i.stack.imgur.com/hYo8y.png
[2]: https://i.stack.imgur.com/xPjCK.png
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