SeparateWrite.java

import java.util.*;
import java.nio.charset.Charset;

public class SeparateWrite {
 static class Writer implements Runnable {
 private Map<Integer, String> map;
 private Random rand = new Random();
 private int id;

 Writer(int id) {
 this.map = new HashMap<>();
 this.id = id;
 }

 private String randomString() {
 byte[] array = new byte[10];
 rand.nextBytes(array);
 String randomString = new String(array, Charset.forName("ASCII"));
 return randomString;
 }

 private int randomBoundedInt() {
 return rand.nextInt(10001);
 }

 public void run() {
 for (int i = 0; i < 1000; i++) {
 int idx = randomBoundedInt();
 String item = randomString();
 map.put(idx, item);
 System.out.printf("%d: %s\n", idx, item);
 }
 }
 }

 public static void main(String[] args) {
 int numThreads = 1;

 if (args.length == 0) {
 System.err.println("Usage: java SeparateWrite [num of threads]");
 System.exit(1);
 } else {
 try {
 numThreads = Integer.parseInt(args[0]);
 } catch (NumberFormatException e) {
 System.err.println("Usage: java SeparateWrite [num of threads]");
 System.exit(1);
 }
 }

 List<Thread> threadPool = new ArrayList<>();

 for (int i = 0; i < numThreads; i++) {
 Writer w = new Writer(i);
 threadPool.add(new Thread(w));
 }

 for (Thread t : threadPool) {
 t.start();
 }

 for (Thread t : threadPool) {
 try {
 t.join();
 } catch (InterruptedException e) {
 System.err.println("Error encountered when trying to join");
 }
 }
 }
}