List getting threadsafe with removing items - multithreading

I'm trying to remove items from a list until its empty with multithreading.
Code:
public void testUsers() {
final List<User> users = userDao.findAll();
final int availableProcessors = Runtime.getRuntime().availableProcessors() * multiplier;
final List<String> loggingList = Lists.newArrayList();
final List<Integer> sizeChecked = Lists.newArrayList();
int totalSizeChecked = 0;
int sizeList = users.size();
ExecutorService executorService = Executors.newFixedThreadPool(availableProcessors);
for (int i = 0; i < availableProcessors; i++) {
createThread(executorService, users, loggingList, sizeChecked);
}
executorService.shutdown();
try {
// wait for all threads to die
executorService.awaitTermination(1, TimeUnit.HOURS);
} catch (InterruptedException ex) {
}
for (Integer count : sizeChecked) {
totalSizeChecked += count;
}
Assert.assertTrue(totalSizeChecked==sizeList);
}
private void createThread(ExecutorService executorService, final List<User> users,
final Collection<String> loggingList, final List<Integer> sizeChecked) {
executorService.execute(new Runnable() {
#Override
public void run() {
int totalChecked = 0;
while (!users.isEmpty()) {
User user = null;
synchronized (users) {
if (!users.isEmpty()) {
user = users.remove(0);
}
}
totalChecked++;
if (user != null) {
String reason = checkUser(user);
if (reason != null) {
loggingList.add(reason);
}
} else {
LOGGER.info("user is null");
}
}
sizeChecked.add(totalChecked);
}
});
}
Now I was thinking this couldn't be so wrong cause I made the list synchronised for removing the first item.
I'm testing with a multiplier of 6.(on prod it will be lowered to 1-2)
I get this in the email :
The batch was not correctly executed.
Size of accounts that must be checked : 28499. Size of accounts that have been checked: 25869
What do I wrong to get it threadsafe?

List<Integer> sizeChecked is not thread safe. Therefore you cannot add elements in parallel in it.
Synchronize your add operation or use a thread-safe structure. If sizeChecked is just a counter, use an AtomicLong instead and make each thread increment it.

Related

Worker stop in the middle and not updating progress bar

I'm trying to load information with worker and using reportprogress to update progress bar until finshing, but the worker stop working and doesn't finish the for loop or continue after several minutes. I don't know what's the problem and I tried every post here I can find related to this problem and didn't get anything. I hope I can finally get an answer posting my problem here.
Here's the relevant code:
public class Class1
{
public BackgroundWorker unit_read_data_setting_Worker;
public Class1()
{
unit_read_data_setting_Worker = new BackgroundWorker();
unit_read_data_setting_Worker.WorkerReportsProgress = true;
unit_read_data_setting_Worker.WorkerSupportsCancellation = false;
unit_read_data_setting_Worker.DoWork += new DoWorkEventHandler(unit_read_data_setting);
unit_read_data_setting_Worker.ProgressChanged += new ProgressChangedEventHandler(_update_progress);
unit_read_data_setting_Worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(Completed);
}
public void unit_read_data_setting(object sender = null, DoWorkEventArgs e = null)
{
lock (FamilyTreeViewModel.Lock_ParameterList)
{
ObservableCollection<Parameter_UC_ViewModel> _internal_parameter_list =
FamilyTreeViewModel.GetInstance.ParameterList;
if (FamilyTreeViewModel.GetInstance.SelectedUnitSetting != null)
{
if (_internal_parameter_list.Count > 0)
{
for (int i = 0; i < _internal_parameter_list.Count; i++)
{
int startValue = i * 100 / _internal_parameter_list.Count;
unit_read_data_setting_Worker.ReportProgress(startValue);
// do stuff related to the index
// when progress_bar at 76 value, the loop stoppes and cotinue after a minute
}
}
}
}
}
private void _update_progress(object sender, ProgressChangedEventArgs e)
{
FamilyTreeViewModel.GetInstance.Unit_read_data_setting_progress_bar = e.ProgressPercentage;
}
private void Completed(object sender, RunWorkerCompletedEventArgs e)
{
// never gets here but there's no error
}
}

PackageInstaller does not work on MIUI optimization mode

I created a test application for installing apk files. PackageInstaller was used for this. The app works well. However, for Xiaomi in BroadcastReceiver I get the "INSTALL_FAILED_INTERNAL_ERROR: Permission Denied" error. But if you enable developer mode and disable MIUI optimization, then the application also successfully installs packages. I can't get users of my application to force them to turn off the optimization mode, how can I deal with this? Tested on MIUI 11 version
You can detect whether user has MIUI and optimization mode enabled and display a message which will force user to disable it. Use these utility methods (it's a part of Split APKs Installer source code): https://github.com/Aefyr/SAI/blob/master/app/src/main/java/com/aefyr/sai/utils/MiuiUtils.java
It seems as though MIUI 20.2.20 solves this incompatibility. solru's answer checks for this.
In case the GitHub link stops working:
public static boolean isMiui() {
return !TextUtils.isEmpty(Utils.getSystemProperty("ro.miui.ui.version.name"));
}
public static String getMiuiVersionName() {
String versionName = Utils.getSystemProperty("ro.miui.ui.version.name");
return !TextUtils.isEmpty(versionName) ? versionName : "???";
}
public static int getMiuiVersionCode() {
try {
return Integer.parseInt(Objects.requireNonNull(Utils.getSystemProperty("ro.miui.ui.version.code")));
} catch (Exception e) {
return -1;
}
}
public static String getActualMiuiVersion() {
return Build.VERSION.INCREMENTAL;
}
private static int[] parseVersionIntoParts(String version) {
try {
String[] versionParts = version.split("\\.");
int[] intVersionParts = new int[versionParts.length];
for (int i = 0; i < versionParts.length; i++)
intVersionParts[i] = Integer.parseInt(versionParts[i]);
return intVersionParts;
} catch (Exception e) {
return new int[]{-1};
}
}
/**
* #return 0 if versions are equal, values less than 0 if ver1 is lower than ver2, value more than 0 if ver1 is higher than ver2
*/
private static int compareVersions(String version1, String version2) {
if (version1.equals(version2))
return 0;
int[] version1Parts = parseVersionIntoParts(version1);
int[] version2Parts = parseVersionIntoParts(version2);
for (int i = 0; i < version2Parts.length; i++) {
if (i >= version1Parts.length)
return -1;
if (version1Parts[i] < version2Parts[i])
return -1;
if (version1Parts[i] > version2Parts[i])
return 1;
}
return 1;
}
public static boolean isActualMiuiVersionAtLeast(String targetVer) {
return compareVersions(getActualMiuiVersion(), targetVer) >= 0;
}
#SuppressLint("PrivateApi")
public static boolean isMiuiOptimizationDisabled() {
if ("0".equals(Utils.getSystemProperty("persist.sys.miui_optimization")))
return true;
try {
return (boolean) Class.forName("android.miui.AppOpsUtils")
.getDeclaredMethod("isXOptMode")
.invoke(null);
} catch (Exception e) {
return false;
}
}
public static boolean isFixedMiui() {
return isActualMiuiVersionAtLeast("20.2.20") || isMiuiOptimizationDisabled();
}
Ultimately the functions you're looking for are isMiui and isMiuiFixed.

How to avoid java.util.NoSuchElementException

The code below is giving me the error java.util.NoSuchElementException right after I Ctrl+Z
to indicate that the user input is complete. By the looks of it seems as if it does not know how to just end one method without messing with the other scanner object.
I try the hasNext method and I ended up with an infinite loop, either way is not working. As a requirement for this assignment I need to be able to tell the user to use Ctrl+Z or D depending on the operating system. Also I need to be able to read from a text file and save the final tree to a text file please help.
/* sample input:
CSCI3320
project
personal
1 HW1
1 HW2
1 2 MSS.java
2 p1.java
*/
import java.util.Scanner;
import java.util.StringTokenizer;
public class Directory {
private static TreeNode root = new TreeNode("/", null, null);
public static void main(String[] args) {
userMenu();
System.out.println("The directory is displayed as follows:");
root.listAll(0);
}
private static void userMenu(){ //Displays users menu
Scanner userInput = new Scanner(System.in);//Scanner option
int option = 0;
do{ //I believe the problem is here since I am not using userInput.Next()
System.out.println("\n 1. add files from user inputs ");
System.out.println("\n 2. display the whole directory ");
System.out.println("\n 3. display the size of directory ");
System.out.println("\n 0. exit");
System.out.println("\n Please give a selection [0-3]: ");
option = userInput.nextInt();
switch(option){
case 1: addFileFromUser();
break;
case 2: System.out.println("The directory is displayed as follows:");
root.listAll(0);
break;
case 3: System.out.printf("The size of the directory is %d.\n", root.size());
break;
default:
break;
}
}while( option !=0);
userInput.close();
}
private static void addFileFromUser() {
System.out.println("To terminate inp1ut, type the correct end-of-file indicator ");
System.out.println("when you are prompted to enter input.");
System.out.println("On UNIX/Linux/Mac OS X type <ctrl> d");
System.out.println("On Windows type <ctrl> z");
Scanner input = new Scanner(System.in);
while (input.hasNext()) { //hasNext being used Crtl Z is required to break
addFileIntoDirectory(input); // out of the loop.
}
input.close();
}
private static void addFileIntoDirectory(Scanner input) {
String line = input.nextLine();
if (line.trim().equals("")) return;
StringTokenizer tokens = new StringTokenizer(line);
int n = tokens.countTokens() - 1;
TreeNode p = root;
while (n > 0 && p.isDirectory()) {
int a = Integer.valueOf( tokens.nextToken() );
p = p.getFirstChild();
while (a > 1 && p != null) {
p = p.getNextSibling();
a--;
}
n--;
}
String name = tokens.nextToken();
TreeNode newNode = new TreeNode(name, null, null);
if (p.getFirstChild() == null) {
p.setFirstChild(newNode);
}
else {
p = p.getFirstChild();
while (p.getNextSibling() != null) {
p = p.getNextSibling();
}
p.setNextSibling(newNode);
}
}
private static class TreeNode {
private String element;
private TreeNode firstChild;
private TreeNode nextSibling;
public TreeNode(String e, TreeNode f, TreeNode s) {
setElement(e);
setFirstChild(f);
setNextSibling(s);
}
public void listAll(int i) {
for (int k = 0; k < i; k++) {
System.out.print('\t');
}
System.out.println(getElement());
if (isDirectory()) {
TreeNode t = getFirstChild();
while (t != null) {
t.listAll(i+1);
t = t.getNextSibling();
}
}
}
public int size() {
int s = 1;
if (isDirectory()) {
TreeNode t = getFirstChild();
while (t != null) {
s += t.size();
t = t.getNextSibling();
}
}
return s;
}
public void setElement(String e) {
element = e;
}
public String getElement() {
return element;
}
public boolean isDirectory() {
return getFirstChild() != null;
}
public void setFirstChild(TreeNode f) {
firstChild = f;
}
public TreeNode getFirstChild() {
return firstChild;
}
public void setNextSibling(TreeNode s) {
nextSibling = s;
}
public TreeNode getNextSibling() {
return nextSibling;
}
}
}
Exception Details:
/*Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:907)
at java.util.Scanner.next(Scanner.java:1530)
at java.util.Scanner.nextInt(Scanner.java:2160)
at java.util.Scanner.nextInt(Scanner.java:2119)
at Directory.userMenu(Directory.java:36)
at Directory.main(Directory.java:21)*/
Your problem is this line:
option = userInput.nextInt(); //line 24
If you read the Javadoc, you will find that the nextInt() method can throw a NoSuchElementException if the input is exhausted. In other words, there is no next integer to get. Why is this happening in your code? Because you this line is in a loop once that first iteration completes (on the outer while loop) your initial input selection has been consumed. Since this is a homework, I am not going to write the code. But, if you remove the loop, you know this works at least once. Once you try to loop, it breaks. So I will give you these hints:
Change the do/while to a while loop.
Prompt the user once outside the loop.
Recreate the prompt and recapture the user input inside the loop.
For example, the code below can be used for the basis of your outer loop.
import java.util.Scanner;
public class GuessNumberGame {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Guess the secret number: (Hint: the secret number is 1)");
int guess = input.nextInt();
while (guess != 1) {
System.out.println("Wrong guess. Try again: ");
guess = input.nextInt();
}
System.out.println("Success");
input.close();
}
}
The reason why this works is because I don't reuse the same, exhausted, scanner input object to get the next integer. In your example, the initial input is inside the loop. The second time around, that input has already been consumed. Follow this pattern and you should be able to complete your assignment.

Run RichTextBox on its own thread?

Background
I have a RichTextBox control I am using essentially like a console in my WinForms application. Currently my application-wide logger posts messages using delegates and one of the listeners is this RTB. The logger synchronously sends lots of short (less than 100 char) strings denoting event calls, status messages, operation results, etc.
Posting lots of these short messages to the RTB using BeginInvoke provides UI responsiveness until heavy parallel processing starts logging lots of messages and then the UI starts posting items out of order, or the text is far behind (hundreds of milliseconds). I know this because when the processing slows down or is stopped, the console keeps writing for some time afterwords.
My temporary solution was to invoke the UI synchronously and add a blocking collection buffer. Basically taking the many small items from the Logger and combining them in a stringbuilder to be posted in aggregate to the RTB. The buffer posts items as they come if the UI can keep up, but if the queue gets too high, then it aggregates them and then posts to the UI. The RTB is thus updated piece-meal and looks jumpy when lots of things are being logged.
Question
How can I run a RichTextBox control on its own UI thread to keep other buttons on the same Form responsive during frequent but small append operations? From research, I think I need to run an STA thread and call Application.Run() on it to put the RTB on its own thread, but the examples I found lacked substantive code samples and there don't seem to be any tutorials (perhaps because what I want to do is ill advised?). Also I wasn't sure if there where any pitfalls for a single Control being on its own thread relative to the rest of the Form. (ie. Any issues closing the main form or will the STA thread for the RTB just die with the form closing? Any special disposing? etc.)
This should demonstrate the issue once you add 3 Buttons and a RichTextBox to the form. What I essentially want to accomplish is factoring away the BufferedConsumer by having the RTB on its own thread. Most of this code was hacked out verbatim from my main application, so yes, it is ugly.
using System;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
// Fields
private int m_taskCounter;
private static CancellationTokenSource m_tokenSource;
private bool m_buffered = true;
private static readonly object m_syncObject = new object();
// Properties
public IMessageConsole Application_Console { get; private set; }
public BufferedConsumer<StringBuilder, string> Buffer { get; private set; }
public Form1()
{
InitializeComponent();
m_tokenSource = new CancellationTokenSource();
Application_Console = new RichTextBox_To_IMessageConsole(richTextBox1);
Buffer =
new BufferedConsumer<StringBuilder, string>(
p_name: "Console Buffer",
p_appendBuffer: (sb, s) => sb.Append(s),
p_postBuffer: (sb) => Application_Console.Append(sb));
button1.Text = "Start Producer";
button2.Text = "Stop All";
button3.Text = "Toggle Buffering";
button1.Click += (o, e) => StartProducerTask();
button2.Click += (o, e) => CancelAllProducers();
button3.Click += (o, e) => ToggleBufferedConsumer();
}
public void StartProducerTask()
{
var Token = m_tokenSource.Token;
Task
.Factory.StartNew(() =>
{
var ThreadID = Interlocked.Increment(ref m_taskCounter);
StringBuilder sb = new StringBuilder();
var Count = 0;
while (!Token.IsCancellationRequested)
{
Count++;
sb.Clear();
sb
.Append("ThreadID = ")
.Append(ThreadID.ToString("000"))
.Append(", Count = ")
.AppendLine(Count.ToString());
if (m_buffered)
Buffer
.AppendCollection(sb.ToString()); // ToString mimicks real world Logger passing strings and not stringbuilders
else
Application_Console.Append(sb);
Sleep.For(1000);
}
}, Token);
}
public static void CancelAllProducers()
{
lock (m_syncObject)
{
m_tokenSource.Cancel();
m_tokenSource = new CancellationTokenSource();
}
}
public void ToggleBufferedConsumer()
{
m_buffered = !m_buffered;
}
}
public interface IMessageConsole
{
// Methods
void Append(StringBuilder p_message);
}
// http://stackoverflow.com/a/5706085/1718702
public class RichTextBox_To_IMessageConsole : IMessageConsole
{
// Constants
private const int WM_USER = 0x400;
private const int WM_SETREDRAW = 0x000B;
private const int EM_GETEVENTMASK = WM_USER + 59;
private const int EM_SETEVENTMASK = WM_USER + 69;
private const int EM_GETSCROLLPOS = WM_USER + 221;
private const int EM_SETSCROLLPOS = WM_USER + 222;
//Imports
[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, Int32 wMsg, Int32 wParam, ref Point lParam);
[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, Int32 wMsg, Int32 wParam, IntPtr lParam);
// Fields
private RichTextBox m_richTextBox;
private bool m_attachToBottom;
private Point m_scrollPoint;
private bool m_painting;
private IntPtr m_eventMask;
private int m_suspendIndex = 0;
private int m_suspendLength = 0;
public RichTextBox_To_IMessageConsole(RichTextBox p_richTextBox)
{
m_richTextBox = p_richTextBox;
var h = m_richTextBox.Handle;
m_painting = true;
m_richTextBox.DoubleClick += RichTextBox_DoubleClick;
m_richTextBox.MouseWheel += RichTextBox_MouseWheel;
}
// Methods
public void SuspendPainting()
{
if (m_painting)
{
m_suspendIndex = m_richTextBox.SelectionStart;
m_suspendLength = m_richTextBox.SelectionLength;
SendMessage(m_richTextBox.Handle, EM_GETSCROLLPOS, 0, ref m_scrollPoint);
SendMessage(m_richTextBox.Handle, WM_SETREDRAW, 0, IntPtr.Zero);
m_eventMask = SendMessage(m_richTextBox.Handle, EM_GETEVENTMASK, 0, IntPtr.Zero);
m_painting = false;
}
}
public void ResumePainting()
{
if (!m_painting)
{
m_richTextBox.Select(m_suspendIndex, m_suspendLength);
SendMessage(m_richTextBox.Handle, EM_SETSCROLLPOS, 0, ref m_scrollPoint);
SendMessage(m_richTextBox.Handle, EM_SETEVENTMASK, 0, m_eventMask);
SendMessage(m_richTextBox.Handle, WM_SETREDRAW, 1, IntPtr.Zero);
m_painting = true;
m_richTextBox.Invalidate();
}
}
public void Append(StringBuilder p_message)
{
var WatchDogTimer = Stopwatch.StartNew();
var MinimumRefreshRate = 2000;
m_richTextBox
.Invoke((Action)delegate
{
// Last resort cleanup
if (WatchDogTimer.ElapsedMilliseconds > MinimumRefreshRate)
{
// m_richTextBox.Clear(); // Real-world behaviour
// Sample App behaviour
Form1.CancelAllProducers();
}
// Stop Drawing to prevent flickering during append and
// allow Double-Click events to register properly
this.SuspendPainting();
m_richTextBox.SelectionStart = m_richTextBox.TextLength;
m_richTextBox.SelectedText = p_message.ToString();
// Cap out Max Lines and cut back down to improve responsiveness
if (m_richTextBox.Lines.Length > 4000)
{
var NewSet = new string[1000];
Array.Copy(m_richTextBox.Lines, 1000, NewSet, 0, 1000);
m_richTextBox.Lines = NewSet;
m_richTextBox.SelectionStart = m_richTextBox.TextLength;
m_richTextBox.SelectedText = "\r\n";
}
this.ResumePainting();
// AutoScroll down to display newest text
if (m_attachToBottom)
{
m_richTextBox.SelectionStart = m_richTextBox.Text.Length;
m_richTextBox.ScrollToCaret();
}
});
}
// Event Handler
void RichTextBox_DoubleClick(object sender, EventArgs e)
{
// Toggle
m_attachToBottom = !m_attachToBottom;
// Scroll to Bottom
if (m_attachToBottom)
{
m_richTextBox.SelectionStart = m_richTextBox.Text.Length;
m_richTextBox.ScrollToCaret();
}
}
void RichTextBox_MouseWheel(object sender, MouseEventArgs e)
{
m_attachToBottom = false;
}
}
public class BufferedConsumer<TBuffer, TItem> : IDisposable
where TBuffer : new()
{
// Fields
private bool m_disposed = false;
private Task m_consumer;
private string m_name;
private CancellationTokenSource m_tokenSource;
private AutoResetEvent m_flushSignal;
private BlockingCollection<TItem> m_queue;
// Constructor
public BufferedConsumer(string p_name, Action<TBuffer, TItem> p_appendBuffer, Action<TBuffer> p_postBuffer)
{
m_name = p_name;
m_queue = new BlockingCollection<TItem>();
m_tokenSource = new CancellationTokenSource();
var m_token = m_tokenSource.Token;
m_flushSignal = new AutoResetEvent(false);
m_token
.Register(() => { m_flushSignal.Set(); });
// Begin Consumer Task
m_consumer = Task.Factory.StartNew(() =>
{
//Handler
// .LogExceptions(ErrorResponse.SupressRethrow, () =>
// {
// Continuously consumes entries added to the collection, blocking-wait if empty until cancelled
while (!m_token.IsCancellationRequested)
{
// Block
m_flushSignal.WaitOne();
if (m_token.IsCancellationRequested && m_queue.Count == 0)
break;
// Consume all queued items
TBuffer PostBuffer = new TBuffer();
Console.WriteLine("Queue Count = " + m_queue.Count + ", Buffering...");
for (int i = 0; i < m_queue.Count; i++)
{
TItem Item;
m_queue.TryTake(out Item);
p_appendBuffer(PostBuffer, Item);
}
// Post Buffered Items
p_postBuffer(PostBuffer);
// Signal another Buffer loop if more items were Queued during post sequence
var QueueSize = m_queue.Count;
if (QueueSize > 0)
{
Console.WriteLine("Queue Count = " + QueueSize + ", Sleeping...");
m_flushSignal.Set();
if (QueueSize > 10 && QueueSize < 100)
Sleep.For(1000, m_token); //Allow Queue to build, reducing posting overhead if requests are very frequent
}
}
//});
}, m_token, TaskCreationOptions.LongRunning, TaskScheduler.Default);
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool p_disposing)
{
if (!m_disposed)
{
m_disposed = true;
if (p_disposing)
{
// Release of Managed Resources
m_tokenSource.Cancel();
m_flushSignal.Set();
m_consumer.Wait();
}
// Release of Unmanaged Resources
}
}
// Methods
public void AppendCollection(TItem p_item)
{
m_queue.Add(p_item);
m_flushSignal.Set();
}
}
public static partial class Sleep
{
public static bool For(int p_milliseconds, CancellationToken p_cancelToken = default(CancellationToken))
{
//p_milliseconds
// .MustBeEqualOrAbove(0, "p_milliseconds");
// Exit immediate if cancelled
if (p_cancelToken != default(CancellationToken))
if (p_cancelToken.IsCancellationRequested)
return true;
var SleepTimer =
new AutoResetEvent(false);
// Cancellation Callback Action
if (p_cancelToken != default(CancellationToken))
p_cancelToken
.Register(() => SleepTimer.Set());
// Block on SleepTimer
var Canceled = SleepTimer.WaitOne(p_milliseconds);
return Canceled;
}
}
}
Posting answer as per the OP's request:
You can integrate my example of a Virtualized, High-Performance, Rich, highly customizable WPF log Viewer in your existing winforms application by using the ElementHost
Full source code in the link above

Implementing Runnable and extending thread

I have been given the task of running two threads one using extends and one using implements runnable, the output is meant to be similair to this
F(0)
F(1)
F(2)
.........
S(0)
S(1)
S(2)
So far im getting
F(0)
S(1)
F(1)
F(2)
S(2)
public class Fast implements Runnable
{
/** Creates a new instance of Fast */
public void run()
{
for(int i = 0; i <= 9; i++)
{
try
{
System.out.println("F("+ i + ")");
Thread.sleep(200);
}
catch(InterruptedException e)
{
String errMessage = e.getMessage();
System.out.println("Error" + errMessage);
}
}
}
}
and
public class Slow extends Thread
{
/** Creates a new instance of Slow */
public void run()
{
for(int i = 0; i <= 6; i++)
{
try
{
System.out.println("S("+ i + ")");
Thread.sleep(400);
}
catch(InterruptedException e)
{
String errMessage = e.getMessage();
System.out.println("Error" + errMessage);
}
}
}
}
With the main
public class Main
{
public static void main(String args[])
{
Fast f = new Fast();
Slow s = new Slow();
Thread ft = new Thread(f);
ft.start();
s.start();
}
}
It seems like you want to get Slow to run after Fast? Your output is pretty much what i would expect. Eventually F will finish faster (just 2000ms) and S will still be running (2800ms). I'm not what this assignment has got to do with implementing Runnable or extending Thread since they give you the same end-result.
If you want F to finish completely before S you need to join on F first, like this:
Fast f = new Fast();
Slow s = new Slow();
Thread ft = new Thread(f);
ft.start();
ft.join();
s.start();
That will wait for ft to complete before even starting S giving you the desired output F1, F2,... S1,S2,...

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