[Java] Wait a few seconds for user input

The code should look something like this:

input = scan.nextLine();
long referenceTime = new Date().getTime(); //in milliseconds i guess
long currentTime = new Date().getTime();
while ((currentTime - referenceTime) < 5000) {
   //wait for user input
   currentTime = new Date().getTime();
}

rami wroteThe code should look something like this:

input = scan.nextLine();
long referenceTime = new Date().getTime(); //in milliseconds i guess
long currentTime = new Date().getTime();
while ((currentTime - referenceTime) < 5000) {
   //wait for user input
   currentTime = new Date().getTime();
}

Won't that totally screw the CPU? Unless there is some kind of intelligent optimization/compilation...

How about you create a new thread and make it sleep for 5 seconds while waiting for the user input

Hm... Here's the dilemma: If you use the sleep function the user won't be able to input anything and if you use the loop you have more flexibility but less efficiency. I guess you can add

Thread.sleep(50);

in the loop to add some efficiency.
Source http://stackoverflow.com/questions/580419/how-can-i-stop-a-java-while-loop-from-eating-50-of-my-cpu

I'm not sure how Java manages threads (or whether it just leaves it up to the OS), but creating a new thread is definitely not the way to go. User input should always be captured on the main thread, that is the UI thread.

The loop suggested by rami should do the trick, but yes that's too much work for the CPU to achieve something as simple as that.

I agree with Paladin. There is no way for you to do this, unless you go for a context switch (threading or processes). I don't know Java well enough to give you a code unfortunately.

On the other hand, you asked if this is the good way to go, and to me, it seems a bit too complicated.

You want to put a timeout on a user's input, and that's great. Can you give us more background about the app, so we can discuss other approaches?

There are dozens of ways you can do this. I can think of three quick ways each with its own strength.

1) Quick and dirty as a hack, you spawn a new thread to read input and interrupt it from the main thread after a delay. Definitely worst implementation.
2) Detailed and clean, classic case of consumer/producer, make use of wait(), notify()
3) Using the latest java concurrency api, haven't used those before.

Either way, I think you're approaching it wrong, as rahmu said, what's the background of the application?

@xterm: Got any good doc about the Java concurrency you mention?

xterm wrote1) Quick and dirty as a hack, you spawn a new thread to read input and interrupt it from the main thread after a delay. Definitely worst implementation.

But in this case the user's input will not be visible on the UI until you marshal it to the UI thread, right?

rahmu wrote@xterm: Got any good doc about the Java concurrency you mention?

I don't know about good, but here are the official docs. Sadly I haven't placed much effort, but i presume what YOU would be interested in is Futures.

P.S. to All: Make no mistake about the entire concurrency paradigm in Java, the all powerful and mighty EE makes use of it extensively.

Kassem wroteBut in this case the user's input will not be visible on the UI until you marshal it to the UI thread, right?

You would think, except Java doesn't complain about accessing objects spawned by different threads than the owner. Unless they changed it, which i don't think they did.

Quick Update: Swing no longer allows manipulating its objects on anything other than its own thread.

Leonedes wroteI'd like to to stop running the while loop if the boolean value is set to false OR the user enters lets say "Stop" while the program is running.

while ( boolean == True)     
{
    input = scan.nextLine(); 

    if (somethingHappens() || input == "Stop")        // Check correct Java syntax for comparing strings
    {
        boolean = False;
    }
}

I don't know how correct a Java syntax this is. Don't hesitate to ask if you're unsure about anything.

let me give you some guidelines for the solution, I hope they help you with what you are doing:
1 in the main class, you create a boolean variable, name it "userStop, and set it to false;
2 you create a while loop to check if the website has changed, within this loop, you put an if-condition to check if the userStop OR the website changed is true, you break the loop.
3 you create another thread (from within the main) that asks for user input, if it gets it within the specified time (5 seconds) then you set userStop accordingly. else, you stop the thread, your userStop variable will remain false and your loop will just continue until the website is changed.
4 you can make the loop sleep for sometime for optimisation.

I hope this solution helps you, it's just a midnight thought that I wanted to share :)

could you please be more specific with what you need this function for? I am suspecting you want to use it for some DOS attacks :P

I cant get the program to stop refreshing the page whenever I want to, I can only terminate it totally.

can't you have the page reading loop in a new thread, and pause/resume it from the main thread?