Strange behavior of threads - multithreading

I’m writing an application that communicates with some hardware using the MODBUS protocol.
I'm using this sample from Code Project.
While trying to optimize the code (mainly the PollFunction function), I've encountered with a very strange threads lock.
Instead of sending each line of string to the DoGUIUpdate delagate, I'm constructing a string array and sending it as a whole.
Doing so causes the application to crush with a System.Reflection.targetParametercountException: Parameter count mismatch error.
The original code:
public delegate void GUIUpdate(string paramString);
public void DoGUIUpdate(string paramString)
{
if (InvokeRequired)
BeginInvoke(new GUIUpdate(DoGUIUpdate), paramString);
else
lstRegisterValues.Items.Add(paramString);
}
private void PollFunction()
{
...
string itemString;
for (int i = 0; i < pollLength; i++)
{
itemString = "[" + Convert.ToString(pollStart + i + 40001) + "] , MB[" + Convert.ToString(pollStart + i) + "] = " + values[i];
DoGUIUpdate(itemString);
}
}
My code:
public delegate void GUIUpdate2(string[] paramString);
public void DoGUIUpdate2(string[] paramString)
{
if (InvokeRequired)
BeginInvoke(new GUIUpdate2(DoGUIUpdate2), paramString);
else
{
lstRegisterValues.Items.Clear();
lstRegisterValues.Items.AddRange(paramString);
}
}
string[] valuesStrings;
private void PollFunction()
{
...
valuesStrings = new string[pollLength];
for (int i = 0; i < pollLength; i++)
{
valuesStrings[i] = "[" + Convert.ToString(pollStart + i + 40001) + "] , MB[" + Convert.ToString(pollStart + i) + "] = " + values[i];
}
DoGUIUpdate2(valuesStrings);
}
Any advice will be welcome.

i think BeginInvoke(new GUIUpdate2(DoGUIUpdate2), paramString); is the problem...
the second parameter of "begininvoke" accepts a param object[] params which will result in the call DoGuiUpdate(string1,string2,string3) which is not what you want...
try encapsulate in the following way:
BeginInvoke(new GUIUpdate2(DoGUIUpdate2), new[]{ paramString });

Related

Accessing Current SharedPreferences Data from Background Services

My app uses a countdown timer in the background in a class that extends Services. The background running service is designed to access the Sharedpreferences data of the app. During the countdown, a particular integer in the Sharedpreferences changes value and the updated value is expected to be accessed in the onFinish() call of the countdown timer. The problem now is that the Service don't read the updated valued from the Sharedpreferences but rather returns the initial value at the point the background service started.
I saw somewhere that the solution to the problem is to use
PreferenceManager.getDefaultSharedPreferences()
instead of getSharedPrefences to be able access the current SharedPreferences value. I implemented this recommendation but the problem persist.
Please somebody should help me out because trying to figure out this is taking too much of my time.
My code is here:
public class BroadcastService extends Service {
DatabaseHelperClass myDatabase = new DatabaseHelperClass(this);
private SharedPreferences defaultSharedPreferences, sharedPreferences, staffSignedIn;
private SharedPreferences.Editor staffEditor, defaultSharedPreferencesEditor;
int countSignIn;
private SimpleDateFormat simpleDateFormatII;
Long timeLeftInMiliseconds;
private final static String TAG = "BroadcastService";
public static final String COUNTDOWN_BR = "com.cenitscitech.www.etimebook.countdown_br";
Intent bi = new Intent(COUNTDOWN_BR);
CountDownTimer cdt = null;
#Override
public void onCreate() {
super.onCreate();
defaultSharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
defaultSharedPreferencesEditor = defaultSharedPreferences.edit();
sharedPreferences = getSharedPreferences("setTime", MODE_PRIVATE);
//staffSignedIn = getSharedPreferences("present", MODE_PRIVATE);
//countSignIn = staffSignedIn.getInt("max", 0);
//staffEditor = staffSignedIn.edit();
simpleDateFormatII = new SimpleDateFormat("MMM EEE dd, yyyy HH:mm");
Log.i(TAG, "Starting timer in broadcast receiver...");
Log.i(TAG, "max Count Obtained onBroadcastCreate: "+defaultSharedPreferences.getInt("max", 0));
}
#Override
public void onDestroy() {
//cdt.cancel();
Log.i(TAG, "Timer in broadcast receiver cancelled");
super.onDestroy();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
timeLeftInMiliseconds = intent.getLongExtra("timeLeft", 0L);
cdt = new CountDownTimer(timeLeftInMiliseconds, 1000) {
#Override
public void onTick(long millisUntilFinished) {
SharedPreferences defaultShared = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
Log.i(TAG, "Countdown seconds remaining: " + millisUntilFinished / 1000);
/*bi.putExtra("countdown", millisUntilFinished);
sendBroadcast(bi);*/
}
#Override
public void onFinish() {
SharedPreferences defaultSharedPreferences2 = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
countSignIn = defaultSharedPreferences2.getInt("max", 0);
Log.i(TAG, "Timer finished");
bi.putExtra("countdown", "Timer finished");
sendBroadcast(bi);
StringBuilder phoneBuilder = new StringBuilder();
Calendar cStart = Calendar.getInstance();
cStart.set(Calendar.HOUR_OF_DAY, 0);
cStart.set(Calendar.MINUTE, 0);
cStart.set(Calendar.SECOND, 0);
Long cStartLong = cStart.getTimeInMillis();
Calendar cEnd = Calendar.getInstance();
cEnd.set(Calendar.HOUR_OF_DAY, 23);
cEnd.set(Calendar.MINUTE, 59);
cEnd.set(Calendar.SECOND, 59);
Long cEndLong = cEnd.getTimeInMillis();
String[] conditionsElements;
Log.i(TAG + " onFinish", "MAXIMUM COUNT OBTAINED: " + defaultSharedPreferences2.getInt("max", 0));
Log.i(TAG + " onFinish", "MAXIMUM COUNT OBTAINED: " + countSignIn);
if (defaultSharedPreferences2.getInt("max", 0) > 0) {
Log.i(TAG + " onFinish", "CURRENT countSignIn Value: "+countSignIn+"\n"+" max Value: "+defaultSharedPreferences2.getInt("max", 0));
conditionsElements = new String[defaultSharedPreferences2.getInt("max", 0)];
for (int i = 1; i <= defaultSharedPreferences2.getInt("max", 0); i++) {
conditionsElements[i - 1] = defaultSharedPreferences2.getString(Integer.toString(i), "NoElement");
Log.i(TAG + " onFinish", "conditionsElement[" + (i - 1) + "] = " + defaultSharedPreferences2.getString(Integer.toString(i), "NoElement"));
if (i < defaultSharedPreferences2.getInt("max", 0)) {
phoneBuilder.append("MOBILE_NUMBER = ? OR ");
Log.i(TAG + " onFinish", "phoneBuilder[" + (i - 1) + "]: " + phoneBuilder);
//phoneBuilder.append(staffSignedIn.getString(Integer.toString(i), "NoStaff")+"_");
} else if (i == defaultSharedPreferences2.getInt("max", 0)) {
//phoneBuilder.append(staffSignedIn.getString(Integer.toString(i), "NoStaff"));
phoneBuilder.append("MOBILE_NUMBER = ?");
Log.i(TAG + " onFinish", "phoneBuilder[final]: " + phoneBuilder);
}
}
} else {
Log.i(TAG + " onFinishInsideElse", "CURRENT countSignIn Value: "+countSignIn+"\n"+" max Value: "+defaultSharedPreferences2.getInt("max", 0));
conditionsElements = new String[1];
conditionsElements[0] = "NoElement";
phoneBuilder.append("MOBILE_NUMBER = ?");
}
Cursor cursor = myDatabase.queryAbsentStaff(SURNAME_COLUMN + ", " + FIRST_NAME_COLUMN + ", " + MIDDLE_NAME_COLUMN + ", " + MOBILE_NUMBER_COLUMN + ", " + DATE_COLUMN,
SURNAME_COLUMN + ", " + FIRST_NAME_COLUMN + ", " + MIDDLE_NAME_COLUMN + ", " + MOBILE_NUMBER_COLUMN + ", " + DATE_COLUMN,
phoneBuilder.toString(),
conditionsElements);
Log.i(TAG + " onFinish", "\n" + "SET TIMES:" + "\n" + cStartLong + "\n" + cEndLong + "\n" + "RETURNED ROWS:" + "\n" + cursor.getCount());
/*staffEditor.putInt("max", 0);
staffEditor.apply();
for(int i=0; i<staffSignedIn.getInt("totalStaff", 100); i++){
staffEditor.putString(Integer.toString((i+1)), "empty").apply();
}*/
if(cursor.moveToFirst()){
for (int i = 0; i < cursor.getCount(); i++) {
if(myDatabase.insertTimeBookRecord(cursor.getString(cursor.getColumnIndex(SURNAME_COLUMN)), cursor.getString(cursor.getColumnIndex(FIRST_NAME_COLUMN)),
cursor.getString(cursor.getColumnIndex(MIDDLE_NAME_COLUMN)), cursor.getString(cursor.getColumnIndex(MOBILE_NUMBER_COLUMN)),
"ABSENT", Long.toString(System.currentTimeMillis()), 1000000L, "NO", "0000", System.currentTimeMillis(), "notSynced", "notSynced")){
cursor.moveToNext();
if(cursor.isAfterLast()){
cursor.close();
}
}else{
cursor.moveToNext();
if(cursor.isAfterLast()){
cursor.close();
}
}
}
}
Log.i(TAG +" onFinish: ", "max val reset: "+defaultSharedPreferences2.getInt("max", 0));

Problems in using SwingWorker class for reading a file and implementing a JProgressBar

Note: This question may look like a repetition of several question posted on the forum, but I am really stuck on this problem from quite some time and I am not able to solve this issue using the solutions posted for similar questions. I have posted my code here and need help to proceed further
So, here is my issue:
I am writing a Java GUI application which loads a file before performing any processing. There is a waiting time on an average of about 10-15 seconds during which the file is parsed. After this waiting time, what I get see on the GUI is,
The parsed file in the form of individual leaves in the JTree in a Jpanel
Some header information (example: data range) in two individual JTextField
A heat map generated after parsing the data in a different JPanel on the GUI.
The program connects to R to parse the file and read the header information.
Now, I want to use swing worker to put the file reading process on a different thread so that it does not block the EDT. I am not sure how I can build my SwingWorker class so that the process is done in the background and the results for the 3 components are displayed when the process is complete. And, during this file reading process I want to display a JProgressBar.
Here is the code which does the whole process, starting from selection of the file selection menu item. This is in the main GUI method.
JScrollPane spectralFilesScrollPane;
if ((e.getSource() == OpenImagingFileButton) || (e.getSource() == loadRawSpectraMenuItem)) {
int returnVal = fcImg.showOpenDialog(GUIMain.this);
// File chooser
if (returnVal == JFileChooser.APPROVE_OPTION) {
file = fcImg.getSelectedFile();
//JTree and treenode creation
DefaultMutableTreeNode root = new DefaultMutableTreeNode(file);
rawSpectraTree = new JTree(root);
DefaultTreeModel model = (DefaultTreeModel) rawSpectraTree.getModel();
try {
// R connection
rc = new RConnection();
final String inputFileDirectory = file.getParent();
System.out.println("Current path: " + currentPath);
rc.assign("importImagingFile", currentPath.concat("/importImagingFile.R"));
rc.eval("source(importImagingFile)");
rc.assign("currentWorkingDirectory", currentPath);
rc.assign("inputFileDirectory", inputFileDirectory);
rawSpectrumObjects = rc.eval("importImagingFile(inputFileDirectory,currentWorkingDirectory)");
rc.assign("plotAverageSpectra", currentPath.concat("/plotAverageSpectra.R"));
rc.eval("source(plotAverageSpectra)");
rc.assign("rawSpectrumObjects", rawSpectrumObjects);
REXP averageSpectraObject = rc.eval("plotAverageSpectra(rawSpectrumObjects)");
rc.assign("AverageMassSpecObjectToSpectra", currentPath.concat("/AverageMassSpecObjectToSpectra.R"));
rc.eval("source(AverageMassSpecObjectToSpectra)");
rc.assign("averageSpectraObject", averageSpectraObject);
REXP averageSpectra = rc.eval("AverageMassSpecObjectToSpectra(averageSpectraObject)");
averageSpectraMatrix = averageSpectra.asDoubleMatrix();
String[] spectrumName = new String[rawSpectrumObjects.asList().size()];
for (int i = 0; i < rawSpectrumObjects.asList().size(); i++) {
DefaultMutableTreeNode node = new DefaultMutableTreeNode("Spectrum_" + (i + 1));
model.insertNodeInto(node, root, i);
}
// Expand all the nodes of the JTree
for(int i=0;i< model.getChildCount(root);++i){
rawSpectraTree.expandRow(i);
}
DefaultMutableTreeNode firstLeaf = ((DefaultMutableTreeNode)rawSpectraTree.getModel().getRoot()).getFirstLeaf();
rawSpectraTree.setSelectionPath(new TreePath(firstLeaf.getPath()));
updateSpectralTableandChartRAW(firstLeaf);
// List the min and the max m/z of in the respective data fields
rc.assign("dataMassRange", currentPath.concat("/dataMassRange.R"));
rc.eval("source(dataMassRange)");
rc.assign("rawSpectrumObjects", rawSpectrumObjects);
REXP massRange = rc.eval("dataMassRange(rawSpectrumObjects)");
double[] massRangeValues = massRange.asDoubles();
minMzValue = (float)massRangeValues[0];
maxMzValue = (float)massRangeValues[1];
GlobalMinMz = minMzValue;
GlobalMaxMz = maxMzValue;
// Adds the range values to the jTextField
minMz.setText(Float.toString(minMzValue));
minMz.validate();
minMz.repaint();
maxMz.setText(Float.toString(maxMzValue));
maxMz.validate();
maxMz.repaint();
// Update status bar with the uploaded data details
statusLabel.setText("File name: " + file.getName() + " | " + "Total spectra: " + rawSpectrumObjects.asList().size() + " | " + "Mass range: " + GlobalMinMz + "-" + GlobalMaxMz);
// Generates a heatmap
rawIntensityMap = gim.generateIntensityMap(rawSpectrumObjects, currentPath, minMzValue, maxMzValue, Gradient.GRADIENT_Rainbow, "RAW");
rawIntensityMap.addMouseListener(this);
rawIntensityMap.addMouseMotionListener(this);
imagePanel.add(rawIntensityMap, BorderLayout.CENTER);
coordinates = new JLabel();
coordinates.setBounds(31, 31, rawIntensityMap.getWidth() - 31, rawIntensityMap.getHeight() - 31);
panelRefresh(imagePanel);
tabbedSpectralFiles.setEnabledAt(1, false);
rawSpectraTree.addTreeSelectionListener(new TreeSelectionListener() {
#Override
public void valueChanged(TreeSelectionEvent e) {
try {
DefaultMutableTreeNode selectedNode =
(DefaultMutableTreeNode) rawSpectraTree.getLastSelectedPathComponent();
int rowCount = listTableModel.getRowCount();
for (int l = 0; l < rowCount; l++) {
listTableModel.removeRow(0);
}
updateSpectralTableandChartRAW(selectedNode);
} catch (RserveException e2) {
e2.printStackTrace();
} catch (REXPMismatchException e1) {
e1.printStackTrace();
}
}
});
spectralFilesScrollPane = new JScrollPane();
spectralFilesScrollPane.setViewportView(rawSpectraTree);
spectralFilesScrollPane.setPreferredSize(rawFilesPanel.getSize());
rawFilesPanel.add(spectralFilesScrollPane);
tabbedSpectralFiles.validate();
tabbedSpectralFiles.repaint();
rawImage.setEnabled(true);
peakPickedImage.setEnabled(false);
loadPeakListMenuItem.setEnabled(true); //active now
loadPeaklistsButton.setEnabled(true); //active now
propertiesMenuItem.setEnabled(true); // active now
propertiesButton.setEnabled(true); //active now
} catch (RserveException e1) {
JOptionPane.showMessageDialog(this,
"There was an error in the R connection. Please try again!", "Error",
JOptionPane.ERROR_MESSAGE);
} catch (REXPMismatchException e1) {
JOptionPane.showMessageDialog(this,
"Operation requested is not supported by the given R object type. Please try again!", "Error",
JOptionPane.ERROR_MESSAGE);
}
// hideProgress();
}
}
I tried creating a SwingWorker class, but I am totally confused how I can get all the three outputs on the GUI, plus have a progress bar. It is not complete, but I don't know how to proceed further.
public class FileReadWorker extends SwingWorker<REXP, String>{
private static void failIfInterrupted() throws InterruptedException {
if (Thread.currentThread().isInterrupted()) {
throw new InterruptedException("Interrupted while loading imaging file!");
}
}
// The file that is being read
private final File fileName;
private JTree rawSpectraTree;
private RConnection rc;
private REXP rawSpectrumObjects;
private double[][] averageSpectraMatrix;
private Path currentRelativePath = Paths.get("");
private final String currentPath = currentRelativePath.toAbsolutePath().toString();
final JProgressBar progressBar = new JProgressBar();
// public FileReadWorker(File fileName)
// {
// this.fileName = fileName;
// System.out.println("I am here");
// }
public FileReadWorker(final JProgressBar progressBar, File fileName) {
this.fileName = fileName;
addPropertyChangeListener(new PropertyChangeListener() {
public void propertyChange(PropertyChangeEvent evt) {
if ("progress".equals(evt.getPropertyName())) {
progressBar.setValue((Integer) evt.getNewValue());
}
}
});
progressBar.setVisible(true);
progressBar.setStringPainted(true);
progressBar.setValue(0);
setProgress(0);
}
#Override
protected REXP doInBackground() throws Exception {
System.out.println("I am here... in background");
DefaultMutableTreeNode root = new DefaultMutableTreeNode(fileName);
rawSpectraTree = new JTree(root);
DefaultTreeModel model = (DefaultTreeModel) rawSpectraTree.getModel();
rc = new RConnection();
final String inputFileDirectory = fileName.getParent();
rc.assign("importImagingFile", currentPath.concat("/importImagingFile.R"));
rc.eval("source(importImagingFile)");
rc.assign("currentWorkingDirectory", currentPath);
rc.assign("inputFileDirectory", inputFileDirectory);
rawSpectrumObjects = rc.eval("importImagingFile(inputFileDirectory,currentWorkingDirectory)");
rc.assign("plotAverageSpectra", currentPath.concat("/plotAverageSpectra.R"));
rc.eval("source(plotAverageSpectra)");
rc.assign("rawSpectrumObjects", rawSpectrumObjects);
REXP averageSpectraObject = rc.eval("plotAverageSpectra(rawSpectrumObjects)");
rc.assign("AverageMassSpecObjectToSpectra", currentPath.concat("/AverageMassSpecObjectToSpectra.R"));
rc.eval("source(AverageMassSpecObjectToSpectra)");
rc.assign("averageSpectraObject", averageSpectraObject);
REXP averageSpectra = rc.eval("AverageMassSpecObjectToSpectra(averageSpectraObject)");
averageSpectraMatrix = averageSpectra.asDoubleMatrix();
for (int i = 0; i < rawSpectrumObjects.asList().size(); i++) {
DefaultMutableTreeNode node = new DefaultMutableTreeNode("Spectrum_" + (i + 1));
model.insertNodeInto(node, root, i);
}
// Expand all the nodes of the JTree
for(int i=0;i< model.getChildCount(root);++i){
rawSpectraTree.expandRow(i);
}
return averageSpectra;
}
#Override
public void done() {
setProgress(100);
progressBar.setValue(100);
progressBar.setStringPainted(false);
progressBar.setVisible(false);
}
}
Any help would be very much appreciated.

Using ToneController to get more than one digit

I am new to UCMA and I read Tone Controller example in UCMA sdk 4.0.
I know this is the way you can record tone played by user:
void toneController_ToneReceived(object sender, ToneControllerEventArgs e)
{
Console.WriteLine("Tone Received: " + (ToneId)e.Tone + " (" + e.Tone + ")");
if ((ToneId)e.Tone == ToneId.Tone0)
{
_waitForToneReceivedEventCompleted.Set();
}
else
{
ToneController tc = (ToneController)sender;
tc.Send(e.Tone);
}
}
I want to know if there is a way to find the series of tones received from user not just one ( for example 10 digit), I want to use it for direct dialing.
You can simply do it in a loop:
string tone_received = "";
int number_of_tone_received = 0;
while(number_of_tone_received++ < 10)
{
//Sync; wait for ToneReceivedEvent
_waitForToneReceivedEventCompleted.WaitOne();
_waitForToneReceivedEventCompleted.Reset();
}
_waitForToneReceivedEventCompleted.WaitOne();
void toneController_ToneReceived(object sender, ToneControllerEventArgs e)
{
tone_received = tone_received + e.Tone;
_waitForToneReceivedEventCompleted.Set();
}

ReaderWriter Lock, My code just gives exceptions

I'm trying to implement the Reader Writer Problem .. I don't know what is wrong with it?
can any one help me figure out why?
...................................................
package readerWriterController;
import java.util.ArrayList;
import java.util.Scanner;
public class Main {
public class ReaderThread extends Thread{
String threadName;
public ReaderThread(String threadName){
super(threadName);
}
public void run(){
System.out.println(getName() + " started reading!");
p();
System.out.println(getName() + " Read : " + Main.buffer);
System.out.println(getName() + " finished reading!");
v();
}
private void p() {
semaphore++;
if(isBlocked){ // if writing
try{
System.out.println(getName() + " is blocked!!");
wait();
}catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void v() {
--semaphore;
if(semaphore == 0 )notify();
}
}
public class WriterThread extends Thread{
private String text;
public WriterThread(String threadName, String text){
super(threadName);
this.text = text;
}
public void run(){
System.out.println(getName() +" start writing");
if(!isBlocked && semaphore == 0){
isBlocked = true;
synchronized (buffer) {
System.out.println(getName() +" Writing : " + Main.buffer + " " + text);
Main.buffer += text;
System.out.println(getName() +" finished writing!!" );
notify();
}
isBlocked=false;
}else if(isBlocked || semaphore != 0){ // just else !
System.out.println(getName() + " is blocked!");
try{
wait();
}catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public static String buffer;
public static int readerCounter = 0;
public static int semaphore ;
private volatile boolean isBlocked=false;
//public boolean semaphore ;
public static void main(String[] args) {
//System.out.println(readerCounter);
Scanner input = new Scanner(System.in);
System.out.println("Enter the buffer:");
buffer = input.next();
int Nr, Nw;
System.out.println("Enter the number of readers");
Nr = input.nextInt();
semaphore = 0;
System.out.println("Enter the number of writers");
Nw = input.nextInt();
// for the reader threads ...
String name;
ArrayList<Thread> list = new ArrayList<Thread>();
for(int i = 0 ; i < Nr ; i++){
// get reader info.
System.out.println("Enter reader "+ (i+1) + " name :");
name = input.next();
// pass to thread!!
list.add(new Main().new ReaderThread(name));
}
// for the writer thread ...
String text;
for(int i = 0 ; i < Nw ; i++){
// get reader info.
System.out.println("Enter writer "+ (i+1) + " name :");
name = input.next();
System.out.println("Enter the text to be written by this writer:");
text = input.next();
// pass to thread!!
list.add(new Main().new WriterThread(name, text));
}
for(Thread t : list){
t.start();
}
}
}
it just gives me more and more exceptions !!!
is there a problem if I called notify() while there is no thread waiting ?
I think that can not call wait() on constant String's or global objects.!
I have seen this here!

How do I make so that when I input a value into a scanner if it is not an integer it won't give me an error?

I am writing a program that does simple math problems. What I am trying to do is to make it so that even if I input a string into the the scanner level it will not give me an error. The level is to choose the difficulty of the math problems. I have tried parseInt, but am at a loss of what to do now.
import java.util.Random;
import java.util.Scanner;
public class Test {
static Scanner keyboard = new Scanner(System.in);
static Random generator = new Random();
public static void main(String[] args) {
String level = intro();//This method intorduces the program,
questions(level);//This does the actual computation.
}
public static String intro() {
System.out.println("HI - I am your friendly arithmetic tutor.");
System.out.print("What is your name? ");
String name = keyboard.nextLine();
System.out.print("What level do you choose? ");
String level = keyboard.nextLine();
System.out.println("OK " + name + ", here are ten exercises for you at the level " + level + ".");
System.out.println("Good luck.");
return level;
}
public static void questions(String level) {
int value = 0, random1 = 0, random2 = 0;
int r = 0, score = 0;
int x = Integer.parseInt("level");
if (x==1) {
r = 4;
}
else if(x==2) {
r = 9;
}
else if(x==3) {
r = 50;
}
for (int i = 0; i<10; i++) {
random1 = generator.nextInt(r);//first random number.
random2 = generator.nextInt(r);//second random number.
System.out.print(random1 + " + " + random2 + " = ");
int ans = keyboard.nextInt();
if((random1 + random2)== ans) {
System.out.println("Your answer is correct!");
score+=1;
}
else if ((random1 + random2)!= ans) {
System.out.println("Your answer is wrong!");
}
}
if (score==10 || score==9) {
if (score==10 && x == 3) {
System.out.println("This system is of no further use.");
}
else {
System.out.println("Choose a higher difficulty");
}
System.out.println("You got " + score + " out or 10");
}
else if (score<=8 && score>=6) {
System.out.println("You got " + score + " out or 10");
System.out.println("Do the test again");
}
else if (score>6) {
System.out.println("You got " + score + " out or 10");
System.out.println("Come back for extra lessons");
}
}
}
The first error I see is that you tried to Integer.parseInt() a String "level" instead of the String variable named level
int x = Integer.parseInt("level");
should be
int x = Integer.parseInt(level);
Also, when defining level you can use keyboard.nextInt instead of keyboard.nextLine
String level = keyboard.nextInt();
Then, you wouldn't have to do an Integer.parseInt() operation later on

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