I need to determine how long an if statement was executed. I made a simple piece of code to simplify my case:
import org.joda.time.DateTime;
int a;
void setup() {
int a = 1;
}
void draw() {
if (a==1) {
System.out.println(" a is equal to 1");
}
else {
System.out.println(" a is not equal to 1");
}
}
In Processing, the draw method keeps on being executed forever. So it will constantly check if a is equal to 1. In my program, a's value is going to change dynamically based on Reactivision: if a particular element is detected, a will be equal to 1. If not, it will be equal to 0.
I want to know how long has the if statement been executed (to know how long the particular element will be detected).
If I use:
void draw() {
long startTime = System.nanoTime();
if (a==1) {
System.out.println(" a is equal to 1");
}
long estimatedTime = System.nanoTime() - startTime;
else {
System.out.println(" a is not equal to 1");
}
}
each time the draw method will be executed to check if a is equal to 1, it will reset startTime to the current time so it won't be able to add the time already elapsed.
I thought of using joda time, but is there a way to make it "record" how long the if statement was executed ?
The standard way to measure elapsed time in Java is use System.nanoTime() as a benchmark.
long startTime = System.nanoTime();
if (a==1) {
System.out.println(" a is equal to 1");
}
long estimatedTime = System.nanoTime() - startTime;
You should not use System.currentTimeMillis(), see this answer for why.
edit. To see how long a == 1:
import org.joda.time.DateTime;
int a;
long startTime = null;
void setup() {
int a = 1;
startTime = System.nanoTime();
}
void draw() {
if (a==1) {
System.out.println(" a is equal to 1");
}
else {
long estimatedTime = System.nanoTime() - startTime;
System.out.println(" a is not equal to 1" + "took" + estimatedTime);
}
}
Related
I want to try practicing avoiding using static methods/variables when not needed, because I've heard/seen/been told that you want to avoid using them when you can. I decided to make a simple password cracker in Java:
import java.util.Random;
public class PasswordCracker
{
public static void main(String args[])
{
PasswordCracker pwcSimulation = new PasswordCracker();
long totalTimeSpentCracking = 0;
int numSimulations = 100;
for(int i = 0; i < numSimulations; i++)
{
System.out.println(pwcSimulation.PasswordCrackingSimulation());
}
}
long PasswordCrackingSimulation()
{
long startTime = System.currentTimeMillis();
int upperBound = 999999;
Random rand = new Random();
int randomPassword = rand.nextInt(upperBound);
int passwordGuess;
for(int i = 0; i <= upperBound; i++)
{
passwordGuess = i;
if(passwordGuess == randomPassword)
{
System.out.println("password Guessed correctly, the password was: " + randomPassword);
break;
}
/*else
{
System.out.println("Your inputted password is incorrect, please try again.");
}*/
}
long endTime = System.currentTimeMillis();
long timeSpentCracking = (endTime - startTime);
System.out.println("The program took " + timeSpentCracking + "ms OR ~" + ((timeSpentCracking/1000) % 60) + " seconds to complete");
return timeSpentCracking;
}
}
first instantiated a new class (hopefully i did this they way you should?) to avoid having to use a static method for the method PasswordCrackingSimulation. Now i'm having trouble returning a value from the method. The printline in the loop will always print 0, so I know that it isn't taking the returned value in the method. Any help would be lovely :) just trying to learn
No, you're doing everything correctly.
You're returning how long it takes in milliseconds to crack that password.
The answer is less than 1 millisecond. That 0 you see? That's because your method is returning 0. It is doing that because endTime - startTime is zero.
Just write return 1 to test this out yourself - you'll see your print loop print 1 instead.
Alright so I'm still kind of new with methods so forgive me if this seems out of whack. I have a homework problem that has to be a stop watch class with two private data fields startTime and endTime. I need a method named start() that resets startTime to the current time and then stop() that resets endTime to the current time. I also need a getElapsed time method and returns the value.
This is what I got so far:
public class stopWatch {
private double startTime;
private double endTime;
public static void main(String[]args) {
}
public stopWatch(double startTime) {
startTime = System.currentTimeMillis();
}
public void start() {
startTime = System.currentTimeMillis();
}
public void stop() {
endTime = System.currentTimeMillis();
}
public static void getElapsedTime(double startTime, double endTime){
stop() - start()
}
}
Could anybody please send me a step in the right direction? I know i need to subtract the start time from the stopped time and return that as the elapsed, I'm just not sure how to set it up properly.
Couple points.
startTime and endTime should be longs
Constructor should probably not take an argument.
start should probably set endTime to -1
getElapsedTime should be an instance method, not take arguments, return long and return endTime - startTime
to see it work, in your main, create a stopwatch, start the timer, call Thread.sleep(sometime), call stop, print out getElapsed.
I had to create the exact same thing. I wanted a simple Java stopwatch that would start running on my desktop. This is the code from the Stopwatch class. I added some formatting so it doesn't return long numbers that show how many milliseconds since you started the stopwatch. I assume that you would prefer to get something returned that is more meaningful to humans like seconds, minutes, and hours instead of milliseconds.
import java.text.DecimalFormat;
public class Stopwatch
{
// variables
private long startTime;
DecimalFormat twoDigits = new DecimalFormat("00"); // These help me return strings in the correct format
DecimalFormat threeDigits = new DecimalFormat("000"); // These help me return strings in the correct format
// Constructor
Stopwatch()
{
}
void start()
{
startTime = System.currentTimeMillis();
}
public long getStartTime()
{
return startTime;
}
public long getElapsedTime()
{
return System.currentTimeMillis() - startTime;
}
public String getElapsedTimeString()
{
return (String.valueOf(twoDigits.format(getHours())) + ":" + String.valueOf(twoDigits.format(getMinutes())) + ":" + String.valueOf(twoDigits.format(getSeconds())) + "." + String.valueOf(threeDigits.format(getMilliSeconds())));
}
public short getMilliSeconds()
{
return (short)((System.currentTimeMillis() - startTime) % 1000);
}
public byte getSeconds()
{
return (byte)(((System.currentTimeMillis() - startTime) / 1000) % 60);
}
public byte getMinutes()
{
return (byte)(((System.currentTimeMillis() - startTime) / 60000) % 60);
}
public long getHours()
{
return (System.currentTimeMillis() - startTime) / 3600000;
}
}
I am wondering the best way to keep a timer going in the background while a game is played.
I am programming a version of the HiLo game (in Java), which gives a user a certain amount of time to determine a number. If a guess is not correct, the game will tell the user whether the name is too high or too low.
I'm keeping track of time using System.currentTimeMillis() and seeing how much time has elapsed. This seems to work well, and so far I have been checking to see how much time has elapsed each time a new number is entered. For example, currently the app output looks like this:
Welcome to HiLo!
You have 10 seconds to guess a number I'm thinking of between 1 and 100.
> 67
Too high.
> 29
Too low.
Half of your time is gone! Only 5 seconds remains!
> 37
Too high.
> 33
Oops! Time is up - try again.
As you can see, currently, it can only check when I enter a new number how much time is passed.
I have tried creating a thread to start with a timer, however, when I start it, it keeps counting until the time is exhausted, without going on to the thread.run(int guess) which will be run when there is a new guess. I want to be able to still make guesses while the counter runs. Here is my attempt at a new implementation for thread.start():
public void start(int time_sent) throws InterruptedException {
time = time_sent;
startTime = (System.currentTimeMillis() / 1000);
while (1==1) {
long elapsed = ((System.currentTimeMillis() / 1000) - (startTime));
if (elapsed >= (time)) {
System.out.println("Oops! Time is up - try again.");
System.exit(0);
}
else if (elapsed >= (time/2) && !halfWarning) {
System.out.println("Half of your time is gone! Only " + (time/2) + " seconds remains!");
halfWarning = true;
}
}
}
How can I continue running this counter in the background?
This is one more approach:
public void game() {
Scanner scanner = new Scanner(System.in);
int time = 10; // sec
message("You have " + time + " seconds to guess...");
new Thread(new Background(System.currentTimeMillis() / 1000, time)).start();
while (true) {
String s = scanner.next();
if (s.equals("55")) {
message("You win");
System.exit(0);
} else {
message("try again...");
}
}
}
private void message(String str) {
System.out.println(str);
System.out.print("> "); // monit
}
You start 1 thread with behavior implemented in Background class. Next you enter while loop to capture user inputs. The Background thread works in background...
private class Background implements Runnable {
private long startTime;
private long time;
private boolean halfWarning;
private Background(long startTime, long time) {
this.startTime = startTime;
this.time = time;
}
#Override
public void run() {
while (true) {
long now = System.currentTimeMillis() / 1000;
long elapsed = now - startTime;
if (elapsed >= (time / 2) && !halfWarning) {
message("\n Half of your time is gone! Only " + (time / 2) + " seconds remains!");
halfWarning = true;
}
if (elapsed >= time) {
message("\n Oops! Time is up - try again.");
System.exit(0);
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
//ignore
}
}
}
}
Use a ScheduledExecutorService to execute concurrent actions in the future:
ScheduledExecutorService ses = Executors.newSingleThreadScheduledExecutor();
ScheduledFuture<?> half = ses.schedule(new Runnable() {
#Override
public void run() {
System.out.println("Half of your time is gone!");
}
}, time / 2, TimeUnit.SECONDS);
ScheduledFuture<?> full = ses.schedule(new Runnable() {
#Override
public void run() {
System.out.println("Oops! Time is up - try again.");
// System.exit(0) ?
}
}, time, TimeUnit.SECONDS);
// check
if (input == toGuess) {
half.cancel();
full.cancel();
}
You could have a Timer thread that prints out these messages and shuts down the listening program.
It might inspire you :
public static class Game extends TimerTask {
private long start;
private long end;
public Game(long end) {
super();
this.start = System.currentTimeMillis();
this.end = end;
}
#Override
public void run() {
while (System.currentTimeMillis() - start < end)
System.out.println(System.currentTimeMillis());
}
}
public static void main(String[] args) {
TimerTask task = new Game(10000);
Timer timer = new Timer();
timer.schedule(task,0);
}
how I can exit from a loop in one second using Runtime?
I want use this code
public class test {
public static void main(String[] args) {
Runtime runtime = Runtime.getRuntime();
long usedMemory = runtime.totalMemory()-runtime.freeMemory();
int mbytes = (int) usedMemory/1000; // Used memory (Mbytes)
String str="a";
while (somthing < one second ) {
}
}
long startTime = System.currentTimeMillis();
while((System.currentTimeMillis()-startTime)<=1000){
str=str + "a";
}
ok to do this you need to records the start time, and then compare it to the current time as you go.
long start = System.currentTimeMillis();
String str="a";
while (true) {
long now = System.currentTimeMillis();
if (now - start > 1000)
break;
// do your stuff
str=str + "a";
}
System.out.println (str);
The above code will probably spend more time getting the time that doing the stuff you want though
long startTime = System.currentTimeMillis();
while((System.currentTimeMillis()-startTime)<1000){
// Your task goes here
}
Write your code in while loop. It will exit the loop after 1 second.
long start = System.currentTimeMillis();
long end = start + 1000; // 1000 ms/sec
while (System.currentTimeMillis() < end)
{
// Write your code here
}
i think that you can use something like this if you don't really need to use Runtime.
public class test {
public static void main(String[] args) {
long startTime = System.currentTimeMillis();
long currentTime = System.currentTimeMillis();
long usedMemory = runtime.totalMemory()-runtime.freeMemory();
int mbytes = (int) usedMemory/1000; // Used memory (Mbytes)
String str="a";
while (currentTime-startTime<1000) {
currentTime = System.currentTimeMillis();
}
}
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
I found this stopwatch java code from somewhere on the Internet, but it does not seem to be working. I was wondering how to fix this code to make it work. It's supposed to have features to start, stop and reset, and should display the time as hours:minutes:seconds.milliseconds (example: 12:35:17.26). Please help me.
public class StopWatch {
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;
}
//elaspsed time in milliseconds
public long getElapsedTime() {
long elapsed;
if (running) {
elapsed = (System.currentTimeMillis() - startTime);
}
else {
elapsed = (stopTime - startTime);
}
return elapsed;
}
//elaspsed time in seconds
public long getElapsedTimeSecs() {
long elapsed;
if (running) {
elapsed = ((System.currentTimeMillis() - startTime) / 1000);
}
else {
elapsed = ((stopTime - startTime) / 1000);
}
return elapsed;
}
//sample usage
public static void main(String[] args) {
StopWatch s = new StopWatch();
s.start();
//code you want to time goes here
s.stop();
System.out.println("elapsed time in milliseconds: " + s.getElapsedTime());
}
}
This example shows how to start and stop a javax.swing.Timer. Several approaches to formatting are shown here. Reset is left as an exercise.
By the level of your assignment, sounds like your professor wants you to use nested loops, which are not being used in the example you took from the web.
I won't give you the full answer, but it's fairly simple: outer-most loop is for hours, the one inside hours is for minutes, the one inside minutes for seconds, and the one inside seconds for milliseconds. The inner-most loop (milliseconds), is the one that prints the current time.
Something like this:
// 24 hours in a day
for(int hours = 0; hours < 24; hours++)
{
// 60 mins in an hours
for(int minutes = 0; minutes < 60; minutes++)
{
// 60 secs in a min
for(int seconds = 0; seconds < 60; seconds++)
{
// 1000 ms in a sec.
for(int ms = 0; ms < 1000; ms++)
{
System.out.println(hours + ":" + minutes + ":" + seconds + "." + ms);
}
}
}
}
Now make it pretty and add a 1-millisecond delay in the inner-most loop and you are done! :)
If you want to make a stopwatch you must make a Thread. The Java API states all of the functions of a thread. This is necessary, because otherwise you won't be able to pause the timer. This is because the system spends the full runtime on the counting.
Also, the script you provided is used for determining the amount of time a certain calculation took, it's not ment for timing itself.
I suggest you make 2 classes, 1 for the timer and 1 for the GUI. make the GUI with a label, a start-, stop- and reset-button.
Next, make sure the timer-class EXTENDS THREAD (or implements Runnable) and make it a thread. Next implement the functions to either stop the thread or start the thread (your start/stop buttons). The Reset should be easy after that (just set the timer back to 0).
The StopWatch-class could look like this:
public class Stopwatch extends Thread
{
private long startTime;
private boolean started;
public void startThread()
{
this.startTime = System.currentTimeMillis();
this.started = true;
this.start();
}
public void run()
{
while (started)
{
// empty code since currentTimeMillis increases by itself
}
}
public int[] getTime()
{
long milliTime = System.currentTimeMillis() - this.startTime;
int[] out = new int[]{0, 0, 0, 0};
out[0] = (int)(milliTime / 3600000 );
out[1] = (int)(milliTime / 60000 ) % 60;
out[2] = (int)(milliTime / 1000 ) % 60;
out[3] = (int)(milliTime) % 1000;
return out;
}
public void stopThread()
{
this.started = false;
}
}
In the GUI-class you would make start call the 'startThread', stop call the StopWatch.stop(); (which is a Thread-function) and make reset call the reset().
This should get you started with a basic stopwatch. A (bad) example for its useage:
public static void main(String[] args) throws InterruptedException
{
Stopwatch s = new Stopwatch();
s.startThread();
while (true)
{
int[] curTime = s.getTime();
System.out.println(curTime[0] + " : " + curTime[1] + " : " + curTime[2] + " : " + curTime[3]);
}
}
It would actually be more sensible to do the calculations on the currentTimeMillis outside of the threadclass.