Question

Could you possible help me solving the next problem?
I’m trying to use PrintStream with my Threads to make them writing something to different outputs.
The problem is: System.out works perfect, but when I try to add

File f1 = new File("src/task7/simple/1.txt"); 
PrintStream filePRinPrintStream = new PrintStream(f1)

my Thread doesn’t want to write anything, it throws no warning or exception while ordinary printing is main() method is OK.

filePRinPrintStream.println("PREVED");

Here are my code extracts for your information.

public class NamePrinterThread implements Runnable, NamePrinterIF{

    private String name;
    private PrintStream outputStream;
    private long interval;
    private int count;

    @Override
    public void setPrintName(String name) {
        this.name = name;
    }

    @Override
    public void setStream(PrintStream stream) {
        if(stream == null) throw new NullPointerException("PrintStream is null");
        this.outputStream = stream;
    }

    @Override
    public void setInterval(long ms) {
        if(ms <= 0) throw new IllegalArgumentException("Printing interval can't be negative");
        this.interval = ms;
    }

    @Override
    public void setCount(int count) {
        if(count <= 0) throw new IllegalArgumentException("Printing count can't be negative");
        this.count = count;
    }

    @Override
    public void run() {
        for (int i = 0; i < this.count; i++) {
            try {
                outputStream.println(this.name);
                Thread.sleep(interval);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }       
    }

    public void startThread(){
        new Thread(this, name).start();
    }

}

and main method from another class

public static void main(String[] args) {

        File f1 = new File("src/task7/simple/1.txt");

        try(PrintStream filePRinPrintStream = new PrintStream(f1)){ 

            //filePRinPrintStream.println("PREVED");
            NamePrinterIF thread2 = new NamePrinterThread();
            thread2.setCount(20);
            thread2.setInterval(350);
            thread2.setStream(filePRinPrintStream);
            thread2.setPrintName("thread2");

            thread2.startThread();

            filePRinPrintStream.flush();
        } catch(IOException e){
            e.printStackTrace();
        }

        NamePrinterIF thread1 = new NamePrinterThread();
        thread1.setCount(10);
        thread1.setInterval(200);
        thread1.setStream(System.out);
        thread1.setPrintName("thread1");

        thread1.startThread();
    }

Answer 1

Close your printstream in main if you are done.
It would be a good idea if the main terminates after all your threads have terminated, and that you cleanly close the stream then.