Keeps printing output in the Linux terminal until it reads an input

Question

I am a newbie in Java and Object-oriented programming. Let's say I have created a 2d array game grid and initialized the array with characters, which looks like the following:

+++++
+...+
+++++

I want to update the ... with 123. I have the following code:

while (true) {
    if (....) map.printMap();   //what should be the condition here??
    else ...dosomethingelse...;
}

My question is, does there exist a method which I can place in the if condition so that the grid will keeps printing by itself before an input 1? If it detects an input 1, it will stop printing at that moment, execute the else condition to update the grid, then print out as follows:

+++++
+1..+
+++++

After that, it continues to keep printing the updated grid on screen, and follows the same pattern above until all of the ... are updated.

Any idea? Thanks in advance.

You might want to look into something like JCurses for continuously-updated terminal window applications. — 1279343
– 1279343, Commented Jun 11, 2016 at 23:47

Stephen C · Accepted Answer · 2016-06-12 00:35:19Z

1

I would use two threads for this:

Thread 1 periodically (?) updates the screen until a flag is set.
Thread 2 uses a blocking read on console input to get input from the user, and then sets the flag when appropriate.

You could also attempt to do this by calling the available() method, but the specified semantics of that method are such that it is hard (impossible?) to use it portably; i.e. without relying on behavior of the console input stack that could vary from one OS to another.

edited Jun 12, 2016 at 0:35

answered Jun 12, 2016 at 0:03

Stephen C

723k95 gold badges849 silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Harry Tan Over a year ago

Hey Stephen, can you provide a code example for your suggestion?

Stephen C Over a year ago

Nope. Try reading the Java tutorial stream on threads and concurrency: docs.oracle.com/javase/tutorial/essential/concurrency

Wernsey · Accepted Answer · 2016-06-12 01:25:09Z

0

You can try something like the following:

try {
    InputStreamReader reader = new InputStreamReader(System.in);
    BufferedReader buf = new BufferedReader(reader);
    while (true) {
        map.printMap();
        if(!reader.ready()) {
            Thread.sleep(1000);
            continue;
        }
        String command = buf.readLine();
        System.out.println("Command: " + command);
    }
} catch(Exception e ){ 
    e.printStackTrace();
}

answered Jun 12, 2016 at 1:25

Wernsey

5,47926 silver badges39 bronze badges

Collectives™ on Stack Overflow

Keeps printing output in the Linux terminal until it reads an input

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related