import java.util.*;
import java.io.*;

// Somewhat contrived example of deadlock:
public class Deadlock {
    public static void main(String argv[]) {
        FileSystem a = new FileSystem("A");
        FileSystem b = new FileSystem("B");
        new Copier(a,b).start();
        new Copier(b,a).start();                
    } 
}


class FileSystem {
    private String _name;
    public FileSystem(String name) {
        _name = name;
    }
 
    public synchronized void copy(FileSystem destination, String filename) {
        InputStream in = null; /* In real code, = ...*/ ;
        System.out.println(_name+": Opened " + filename + " for reading, about to write");
        destination.writeFile(filename, in);
    }

    public synchronized void writeFile(String filename, InputStream in) {
        // Copy contents of in to file filename
        System.out.println(_name+": Writing file " + filename);
    }
}

// A client thread that just copies the same file
// from one filesystem to another, over and over
// again.
class Copier extends Thread {
    private FileSystem _from;
    private FileSystem _to;

    public Copier(FileSystem fs1, FileSystem fs2) {
        _from = fs1;
        _to = fs2;
    }
        
    public void run() {
        while (true) {
            _from.copy(_to,"foobar.txt");
        }
    }
}