Help with traffic light program and threads

[EasyE]

I need help starting a new thread after I stop the current thread. I keep getting IllegalThreadStateException and I dont know how to fix it.

Exception happens at TrafficMitigation.lambda$0(TrafficMitigation.java: 270)

TrafficMitigation.java

/**
* 
* TrafficMitigation is a GUI application that runs multiple threads concurrently
* to display current time stamps in 1 second intervals and a real-time Traffic 
* light display for three major intersections using multiple JFrame components
* and listeners
*/
 
//=========
//packages
//=========
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.util.concurrent.atomic.*;
 
//=================================
//start of class TrafficMitigation
//=================================
public class TrafficMitigation extends JFrame implements Runnable, ChangeListener {
	private static final long serialVersionUID = 1L;
 
	//==================
	//JFrame components
	//==================
	public static JLabel currentTime = new JLabel();
 
	public static JLabel trafficLight1 = new JLabel();
	private static JLabel trafficLightLabel1;
 
	public static JLabel trafficLight2 = new JLabel();
	private static JLabel trafficLightLabel2;
 
	public static JLabel trafficLight3 = new JLabel();
	private static JLabel trafficLightLabel3;
 
	private static JButton startButton;
	private static JButton pauseButton;
	private static JButton stopButton;
 
	private static JComboBox<Integer> carsJComboBox;
	private static JComboBox<Integer> intersectionJComboBox;
 
	private static JLabel carBoxLabel;
	private static JLabel intersectionBoxLabel;
	private static JLabel header1;
	private static JLabel header2;
	private static JLabel timeLabel;	
 
	private static JSlider car1Slider;
	private static JSlider car2Slider;
	private static JSlider car3Slider;
 
	//==========
	//variables
	//==========
	private static boolean running;
	private static Thread thread;
 
	//=========
	//invoking
	//=========
	private static final AtomicBoolean simIsRunning = new AtomicBoolean(false);
 
	//=============================================
	//invoking and each object gets its own thread
	//=============================================
	private Intersection intersection1 = new Intersection("Intersection 1 Thread", trafficLight1);
	private Intersection intersection2 = new Intersection("Intersection 2 Thread", trafficLight2);
	private Intersection intersection3 = new Intersection("Intersection 3 Thread", trafficLight3);
 
	private Car car1 = new Car("Car 1 Thread", 1, 0);
	private Car car2 = new Car("Car 2 Thread", 300, 0);
	private Car car3 = new Car("Car 3 Thread", 700, 0);
 
	//=======
	//arrays
	//=======
	private Car[] carArray = {car1, car2, car3};
	private Intersection[] intersectionArray = {intersection1, intersection2, intersection3};
	private String[] tableColumnNames = {"Car", "X-Pos", "Y-Pos", "Speed km/h"};
 
	//=========
	//2D array
	//=========
	private Object[][] trafficData = {
			{"Car 1", car1.getPosition(), 0, 0},
			{"Car 2", car2.getPosition(), 0, 0},
			{"Car 3", car3.getPosition(), 0, 0}
	};
 
	//============================
	//JTable for all traffic data
	//============================
	private JTable dataTable = new JTable(trafficData, tableColumnNames);
 
	//============================================
	//displays GUI window to the user and passing
	//it to class Thread. Also Giving the time
	//its own thread
	//============================================
	public static void main(String args[]) {
        TrafficMitigation gui = new TrafficMitigation();        
 
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	    gui.setLocation(440, 100);
	    gui.setResizable(false);
	    gui.setSize(600, 700);
	    gui.setVisible(true);
 
	    thread = new Thread(gui);
 
	    Thread time = new Thread(new Time());
		time.start();
	}
 
	//==================================
	//initializes JFrame components and
	//adds them to the GUI window
	//==================================
	public TrafficMitigation() {
		super("Traffic Congestion Mitigation Company");
 
		setLayout(new GridLayout(9, 1));
 
		trafficLightLabel1 = new JLabel("Traffic Light 1 (1000)");
		trafficLightLabel2 = new JLabel("Traffic Light 2 (2000)");
		trafficLightLabel3 = new JLabel("Traffic Light 3 (3000)");		
 
		startButton = new JButton("Start"); 
		pauseButton = new JButton("Pause");
		stopButton = new JButton("Stop");
 
		carsJComboBox = new JComboBox<>();
		carsJComboBox.addItem(1);
		carsJComboBox.addItem(2);
		carsJComboBox.addItem(3);
		carsJComboBox.addItem(4);
		carsJComboBox.addItem(5);
 
		intersectionJComboBox = new JComboBox<>();
		intersectionJComboBox.addItem(1);
		intersectionJComboBox.addItem(2);
		intersectionJComboBox.addItem(3);
		intersectionJComboBox.addItem(4);
		intersectionJComboBox.addItem(5);
 
		carBoxLabel = new JLabel("Number of Cars");
		intersectionBoxLabel = new JLabel("Number of Intersections");
 
		header1 = new JLabel("Welcome to the Traffic Congestion Mitigation Simulator", SwingConstants.CENTER);
		header2 = new JLabel("\nClick the Start button to begin", SwingConstants.CENTER);
 
		timeLabel = new JLabel("Current Time: ");		
 
		car1Slider = new JSlider(0, 3000);
		car1Slider.setMajorTickSpacing(1000);
		car1Slider.setPaintTicks(true);
		car1Slider.setPaintLabels(true);
 
		car2Slider = new JSlider(0, 3000);
		car2Slider.setMajorTickSpacing(1000);
		car2Slider.setPaintTicks(true);
		car2Slider.setPaintLabels(true);
 
		car3Slider = new JSlider(0, 3000);
		car3Slider.setMajorTickSpacing(1000);
		car3Slider.setPaintTicks(true);
		car3Slider.setPaintLabels(true);		
 
		//=====================================
		//JPanel's for headers, buttons, time,
		//intersections, datatable
		//=====================================
		JPanel headerPanel = new JPanel();
		headerPanel.setLayout(new GridLayout(2,1));
		headerPanel.add(header1);
		headerPanel.add(header2);
 
		JPanel buttonPanel = new JPanel();
		buttonPanel.add(startButton);
		buttonPanel.add(pauseButton);
		buttonPanel.add(stopButton);
 
		JPanel timePanel = new JPanel();
		timePanel.add(timeLabel);
		timePanel.add(currentTime);
 
		JPanel boxPanel = new JPanel();
		boxPanel.add(carBoxLabel);
		boxPanel.add(carsJComboBox);
		boxPanel.add(intersectionBoxLabel);
		boxPanel.add(intersectionJComboBox);
 
		JPanel lightPanel = new JPanel();
   		lightPanel.add(trafficLightLabel1);
		lightPanel.add(trafficLight1);
		lightPanel.add(trafficLightLabel2);
		lightPanel.add(trafficLight2);
		lightPanel.add(trafficLightLabel3);
		lightPanel.add(trafficLight3);
 
		JScrollPane scrollPane = new JScrollPane(dataTable);
		JPanel dataPanel = new JPanel();
		dataPanel.add(scrollPane);		
 
		//================================
		//add JPanels and JSliders to GUI
		//================================
		add(headerPanel);
		add(timePanel);
		add(boxPanel);
		add(buttonPanel);
		add(lightPanel);
		add(car1Slider);
		add(car2Slider);
		add(car3Slider);
		add(dataPanel);
 
		//==============================================
		//add ChangeListners and set Values to JSliders
		//==============================================
		car1Slider.addChangeListener(this);
		car1Slider.setValue(car1.getPosition());
		car2Slider.addChangeListener(this);
		car2Slider.setValue(car2.getPosition());
		car3Slider.addChangeListener(this);				
		car3Slider.setValue(car3.getPosition());
		setButtons();
 
		//=========================
		//setting JTable Viewports
		//=========================
		dataTable.setPreferredScrollableViewportSize(new Dimension(400, 300));
		dataTable.setFillsViewportHeight(true);
 
		//===================
		//run current thread
		//===================
		running = Thread.currentThread().isAlive();		
	}
 
	//==================================
	//handles all JButtons ActionEvents
	//==================================
	private void setButtons() {
 
		//====================================
		//handles "Start" buttton ActionEvent
		//====================================
		startButton.addActionListener((ActionEvent e) -> {
 
			//=================================================================
			//begin threads for cars and intersections when "Start" is clicked
			//=================================================================
			if(!simIsRunning.get()) {
				System.out.println(Thread.currentThread().getName() + " calling start");
 
				try {
					intersection1.start();
					intersection2.start();
					intersection3.start();
					car1.start();
					car2.start();
					car3.start();
					thread.start();  /**Exception thrown here
                                                               */
				}
				catch(IllegalThreadStateException itse) {
					itse.printStackTrace();;
				}
				catch(NullPointerException npe) {
					npe.printStackTrace();
				}				
			}
			simIsRunning.set(true);
		});
 
		//===================================
		//handles "Pause" button ActionEvent
		//===================================
		pauseButton.addActionListener((ActionEvent e) -> {
 
			if(simIsRunning.get()) {
 
				//=====================================================
				//loop through cars and intersections to call paused()
				//=====================================================
				for(Car i: carArray) {
					i.paused();
					System.out.println(Thread.currentThread().getName() + " calling pause");
				}
 
				//=======================================
				//for loop to interrupt sleeping threads
				//=======================================
				for(Intersection i: intersectionArray) {
					i.interrupt();
					i.paused();
				}
 
				//=========================================
				//-changes pause button text to "Continue"
				//-sets simluation running to false
				//=========================================
				pauseButton.setText("Continue");
				simIsRunning.set(false);
			} 
 
			//=============================
			//"Continue" button is clicked
			//=============================
			else {
 
				//====================================
				//for loop to resume threads for cars
				//====================================
				for(Car i:carArray) {
 
					if(i.paused.get()) {
						i.resume();
						System.out.println(Thread.currentThread().getName() + " calling resume");
					}
				}
 
				//=============================================
				//for loop to resume threads for intersections
				//=============================================
				for(Intersection i: intersectionArray) {
					i.resume();
				}
 
				//=========================================
				//-changes continue button text to "Pause"
				//-sets simluation running to true
				//=========================================
				pauseButton.setText("Pause");
				simIsRunning.set(true);
			}
		});
 
		//==================================
		//handles "Stop" button ActionEvent
		//==================================
		stopButton.addActionListener((ActionEvent e) -> {
 
			if(simIsRunning.get()) {
				System.out.println(Thread.currentThread().getName() + " calling stop");
 
				//=================================
				//for loop to stop all car threads
				//=================================
				for(Car i: carArray) {
					i.stop();
				}
 
				//==========================================
				//for loop to stop all intersection threads
				//==========================================
				for(Intersection i: intersectionArray) {
					i.stop();
				}
				simIsRunning.set(false);
			}
		});
	}
 
	//=========================================
	//checks status of the intersection. Stops
	//car threads for running the lights
	//=========================================
	private void getData() {
		if(simIsRunning.get()) {
 
			//======================================
			//switch case for intersection 1 colors
			//======================================
			switch(intersection1.getColor()) {
			case "Red":
				//=====================================
				//red light. Cars drive all the way up
				//to 1st intersection and stop at 989
				//=====================================
				for(Car i: carArray) {
 
					if(i.getPosition() > 989 && i.getPosition() < 1000) {
						i.atStopLight.set(true);
					}
				}
				break;
			case "Green":
				//==================================
				//green light. Keep driving through
				//==================================
				for(Car i:carArray) {
 					if(i.atStopLight.get()) {
						 i.resume();
					}
				}
				break;
			}
 
			//======================================
			//switch case for intersection 2 colors
			//======================================
			switch(intersection2.getColor()) {
			case "Red":
				//=====================================
				//red light. Cars drive all the way up
				//to 2nd intersection and stop at 1989
				//=====================================
				for(Car i: carArray) {
 
					if(i.getPosition() > 1989 && i.getPosition() < 2000) {
						i.atStopLight.set(true);
					}
				}
				break;
			case "Green":
				//==================================
				//green light. Keep driving through
				//==================================
				for(Car i:carArray) {
					if(i.atStopLight.get()) {
						i.resume();
					}
				}
				break;
			}
 
			//======================================
			//switch case for intersection 3 colors
			//======================================
			switch(intersection3.getColor()) {
			case "Red":
				//=====================================
				//red light. Cars drive all the way up
				//to 2nd intersection and stop at 2989
				//=====================================
				for(Car i: carArray) {
 
					if(i.getPosition() > 2989 && i.getPosition() < 3000) {
						i.atStopLight.set(true);
					}
				}
				break;
			case "Green":
				//===================================
				//green light. Keep driving through.
				//loops back to beginning of track
				//===================================
				for(Car i:carArray) {
 
					if(i.atStopLight.get()) {
						i.resume();
					}
				}
				break;
			}
		}
	}
 
	//=============================================================
	//adjusts JSlider values and car speeds as their states change
	//=============================================================
	@Override
	public void stateChanged(ChangeEvent e) {
		try {
			trafficData[0][1] = car1Slider.getValue();
			trafficData[1][1] = car2Slider.getValue();
			trafficData[2][1] = car3Slider.getValue();
 
			trafficData[0][3] = car1.getSpeed() + " km/h";
			trafficData[1][3] = car2.getSpeed() + " km/h";
			trafficData[2][3] = car3.getSpeed() + " km/h";
		}
		catch(NullPointerException npe) {
			npe.printStackTrace();
		}
 
		dataTable.repaint();		
	}
 
	//====================================
	//constantly update JSliders position
	//====================================
	@Override
	public void run() {
 
		while(running) {
 
			if(simIsRunning.get()) {
				car1Slider.setValue(car1.getPosition());
				car2Slider.setValue(car2.getPosition());
				car3Slider.setValue(car3.getPosition());
				getData();
			}
		}
 
	}
}

Time.java

/**
* Time retrieves the current time EST and formats it to display
* hours:minutes:seconds and runs it concurrently while the
* program is running using a thread
*/
 
//=========
//packages
//=========
import java.text.*;
import java.util.*;
 
//====================
//start of class time
//====================
public class Time implements Runnable {
 
	//==========
	//variables
	//==========
	private boolean running;
	private String timePattern = "hh:mm:ss a";
 
	//=========
	//invoking
	//=========
	private Date date = new Date(System.currentTimeMillis());	
	private SimpleDateFormat timeFormat = new SimpleDateFormat(timePattern);	
 
	//============
	//constructor
	//============
	public Time() {
		this.running = Thread.currentThread().isAlive();
	}
 
	//==========================================
	//retrieves the current time and returns it 
	//==========================================
	public String getTime() {
		date = new Date(System.currentTimeMillis());
		return timeFormat.format(date);
	}
 
	//========================================================
	//constantly update current time while program is running
	//========================================================
	@Override
	public void run() {
		while (running) {
			TrafficMitigation.currentTime.setText(getTime());
		}
	}
}

Intersection.java

/**
* Intersection controls the traffic lights at the 3 intersections spaced
* apart on JSlider(0, 3000) evenly at 1000 intervals. Cars can pass through
* the intersections on Green and Yellow but cant pass on Red
*/
 
 
//=========
//packages
//=========
import java.awt.*;
import javax.swing.*;
import java.util.concurrent.atomic.*;
 
//============================
//start of class Intersection
//============================
public class Intersection implements Runnable {
 
	//======
	//array
	//======
	private final String[] COLORS = {"Green", "Yellow", "Red"};
 
	//==========
	//variables
	//==========	
	private JLabel jLabel;
	private int i = 0;
	private Thread thread;	
	private String currentLight = COLORS[i];
	private String threadName;
 
	//=========
	//invoking
	//=========
	private static final AtomicBoolean running = new AtomicBoolean(false);
	public static final AtomicBoolean paused = new AtomicBoolean(false);
 
	//============
	//constructor
	//============
	public Intersection(String name, JLabel j) {
		this.threadName = name;
		this.jLabel = j;
		System.out.println("Creating " + threadName);
	}
 
	//=================================================
	//synchornizes getting traffic light colors: G,Y,R
	//=================================================
	public synchronized String getColor() {
		this.currentLight = COLORS[i];
		return this.currentLight;
	}
 
	//============================
	//pauses and displays threads
	//============================
	public void paused() {
		paused.set(true);
		System.out.println("Pausing " + threadName);
	}
 
	//===========================================
	//synchronizes and displays resuming threads
	//===========================================
	public synchronized void resume() {
		paused.set(false);
		notify();
		System.out.println("Resuming " + threadName);
	}
 
	//============================
	//starts and displays threads
	//============================
	public void start() {
		System.out.println("Starting " + threadName);
		if(thread == null) {
			thread = new Thread(this, threadName);
			thread.start();
		}
	}
 
	//=============================================
	//stops and displays threads using interrupt()
	//=============================================
	public void stop() {
		thread.interrupt();
		running.set(false);
		System.out.println("Stopping " + threadName);
	}
 
	//===================
	//interrupts threads
	//===================
	public void interrupt() {
		thread.interrupt();
	}
 
	//========================
	//display running threads
	//========================
	@Override
	public void run() {
		System.out.println("Running " + threadName);
		running.set(true);
 
		//========================
		//while thread is running
		//========================
		while(running.get()) {
 
			//===================
			//try to synchronize
			//===================
			try {
				synchronized(this) {
 
					//=======================
					//while thread is paused
					//=======================
					while(paused.get()) {
						System.out.println(threadName + " waiting");
						wait();
					}
				}
 
				//==========================================
				//switch case for changing the color of the
				//lights and putting threads to sleep
				//==========================================
				switch (getColor()) {
				case "Green":
					//==========================================
					//green light. goes to sleep for 10 seconds
					//increments 'i' so the next light color is
					//yellow
					//==========================================
					jLabel.setForeground(Color.GREEN.darker());
					jLabel.setText(getColor());
					Thread.sleep(10000);
					i++;
					break;
				case "Yellow":
					//==========================================
					//yellow light. Goes to sleep for 5 seconds
					//increments 'i' so the next light color is
					//red
					//==========================================
					jLabel.setForeground(Color.YELLOW.darker());
					jLabel.setText(getColor());
					Thread.sleep(5000);
					i++;
					break;
				case "Red":
					//=======================================
					//red light. Goes to sleep for 5 seconds
					//sets 'i' back to zero so the next 
					//light color is green
					//=======================================
					jLabel.setForeground(Color.RED.darker());
					jLabel.setText(getColor());
					Thread.sleep(5000);
					i = 0;
					break;
				default:
					break;
				}
			} 
			catch(NullPointerException npe) {
				npe.printStackTrace();
			}
			catch(InterruptedException ex) {
				paused.set(true);
			}
		}
	}
}

Car.java

/**
* Car controls the speed of the cars, the x-position and thread
* starting, pausing, resuming and stopping 
*/
 
//=========
//packages
//=========
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
 
//===================
//start of class Car
//===================
public class Car implements Runnable {
 
	//==========
	//variables
	//==========
	private int xPosition;
	private int speed = 0;
 
	private String threadName = "";
 
	public Thread thread;
 
	//=========
	//invoking
	//=========
	private final AtomicBoolean running = new AtomicBoolean(false);
 
	public final AtomicBoolean atStopLight = new AtomicBoolean(false);
	public final AtomicBoolean paused = new AtomicBoolean(false);
 
	//============
	//constructor
	//============
	public Car(String name, int max, int min) {
		this.threadName = name;
		this.xPosition = ThreadLocalRandom.current().nextInt(min, max);
		System.out.println("Creating " + threadName);
	}
 
	//=====================================
	//determines position of the cars at x
	//=====================================
	public synchronized int getPosition() {
		return xPosition;
	}
 
	//========================================
	//calculates the speed of the cars in kph
	//========================================
	public int getSpeed() {
 
		if(running.get()) {
 
			if(atStopLight.get()) {
				speed = 0;
			}
			else {
				speed = 3 * 60;
			}
		} 
		else
			speed = 0;
		return speed;
	}
 
	//==========================
	//displays threads starting
	//==========================
	public void start() {
		System.out.println("Starting " + threadName);
 
		if(thread == null) {
			thread = new Thread(this, threadName);
			thread.start();
		}
	}
 
	//==========================
	//displays threads stopping
	//==========================
	public void stop() {
		thread.interrupt();
		running.set(false);
		System.out.println("Stopping " + threadName);
	}
 
	//=========================
	//displays threads pausing
	//=========================
	public void paused() {
		paused.set(true);
		System.out.println("Paused " + threadName);
	}
 
	//==========================
	//displays threads resuming
	//==========================
	public synchronized void resume() {
 
		if(paused.get() || atStopLight.get()) {
			paused.set(false);
			atStopLight.set(false);
			notify();
			System.out.println("Resuming " + threadName);
		}
	}
 
	//=========================
	//displays threads running
	//=========================
	@Override
	public void run() {
		System.out.println("Running " + threadName);
		running.set(true);
 
		//===============================
		//while AtomicBoolean is running
		//===============================
		while(running.get()) {
			try {
 
				//=============================
				//while cars x position < 3000
				//=============================
				while(xPosition < 3000) {
					synchronized(this) {
 
						//==============================
						//while paused or at stop light
						//==============================
						while(paused.get() || atStopLight.get()) {
							System.out.println(threadName + " waiting");
							wait();
						}
					}
 
					//=======================
					//Check if still running
					//=======================
					if(running.get()) {
						Thread.sleep(100);
						xPosition += 5;
					}
				}
				xPosition = 0;
			} 
			catch(InterruptedException ie) {
				return;
			}
		}
	}
}

[EasyE]

Edit: I may have put this in the wrong thread previously


I need help starting a new thread after I stop the current thread. I keep getting IllegalThreadStateException and I don't know how to fix it.

Exception happens at TrafficMitigation.lambda$0(TrafficMitigation.java: 270)

TrafficMitigation.java

/**
* 
* TrafficMitigation is a GUI application that runs multiple threads concurrently
* to display current time stamps in 1 second intervals and a real-time Traffic 
* light display for three major intersections using multiple JFrame components
* and listeners
*/
 
//=========
//packages
//=========
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.util.concurrent.atomic.*;
 
//=================================
//start of class TrafficMitigation
//=================================
public class TrafficMitigation extends JFrame implements Runnable, ChangeListener {
	private static final long serialVersionUID = 1L;
 
	//==================
	//JFrame components
	//==================
	public static JLabel currentTime = new JLabel();
 
	public static JLabel trafficLight1 = new JLabel();
	private static JLabel trafficLightLabel1;
 
	public static JLabel trafficLight2 = new JLabel();
	private static JLabel trafficLightLabel2;
 
	public static JLabel trafficLight3 = new JLabel();
	private static JLabel trafficLightLabel3;
 
	private static JButton startButton;
	private static JButton pauseButton;
	private static JButton stopButton;
 
	private static JComboBox<Integer> carsJComboBox;
	private static JComboBox<Integer> intersectionJComboBox;
 
	private static JLabel carBoxLabel;
	private static JLabel intersectionBoxLabel;
	private static JLabel header1;
	private static JLabel header2;
	private static JLabel timeLabel;	
 
	private static JSlider car1Slider;
	private static JSlider car2Slider;
	private static JSlider car3Slider;
 
	//==========
	//variables
	//==========
	private static boolean running;
	private static Thread thread;
 
	//=========
	//invoking
	//=========
	private static final AtomicBoolean simIsRunning = new AtomicBoolean(false);
 
	//=============================================
	//invoking and each object gets its own thread
	//=============================================
	private Intersection intersection1 = new Intersection("Intersection 1 Thread", trafficLight1);
	private Intersection intersection2 = new Intersection("Intersection 2 Thread", trafficLight2);
	private Intersection intersection3 = new Intersection("Intersection 3 Thread", trafficLight3);
 
	private Car car1 = new Car("Car 1 Thread", 1, 0);
	private Car car2 = new Car("Car 2 Thread", 300, 0);
	private Car car3 = new Car("Car 3 Thread", 700, 0);
 
	//=======
	//arrays
	//=======
	private Car[] carArray = {car1, car2, car3};
	private Intersection[] intersectionArray = {intersection1, intersection2, intersection3};
	private String[] tableColumnNames = {"Car", "X-Pos", "Y-Pos", "Speed km/h"};
 
	//=========
	//2D array
	//=========
	private Object[][] trafficData = {
			{"Car 1", car1.getPosition(), 0, 0},
			{"Car 2", car2.getPosition(), 0, 0},
			{"Car 3", car3.getPosition(), 0, 0}
	};
 
	//============================
	//JTable for all traffic data
	//============================
	private JTable dataTable = new JTable(trafficData, tableColumnNames);
 
	//============================================
	//displays GUI window to the user and passing
	//it to class Thread. Also Giving the time
	//its own thread
	//============================================
	public static void main(String args[]) {
        TrafficMitigation gui = new TrafficMitigation();        
 
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	    gui.setLocation(440, 100);
	    gui.setResizable(false);
	    gui.setSize(600, 700);
	    gui.setVisible(true);
 
	    thread = new Thread(gui);
 
	    Thread time = new Thread(new Time());
		time.start();
	}
 
	//==================================
	//initializes JFrame components and
	//adds them to the GUI window
	//==================================
	public TrafficMitigation() {
		super("Traffic Congestion Mitigation Company");
 
		setLayout(new GridLayout(9, 1));
 
		trafficLightLabel1 = new JLabel("Traffic Light 1 (1000)");
		trafficLightLabel2 = new JLabel("Traffic Light 2 (2000)");
		trafficLightLabel3 = new JLabel("Traffic Light 3 (3000)");		
 
		startButton = new JButton("Start"); 
		pauseButton = new JButton("Pause");
		stopButton = new JButton("Stop");
 
		carsJComboBox = new JComboBox<>();
		carsJComboBox.addItem(1);
		carsJComboBox.addItem(2);
		carsJComboBox.addItem(3);
		carsJComboBox.addItem(4);
		carsJComboBox.addItem(5);
 
		intersectionJComboBox = new JComboBox<>();
		intersectionJComboBox.addItem(1);
		intersectionJComboBox.addItem(2);
		intersectionJComboBox.addItem(3);
		intersectionJComboBox.addItem(4);
		intersectionJComboBox.addItem(5);
 
		carBoxLabel = new JLabel("Number of Cars");
		intersectionBoxLabel = new JLabel("Number of Intersections");
 
		header1 = new JLabel("Welcome to the Traffic Congestion Mitigation Simulator", SwingConstants.CENTER);
		header2 = new JLabel("\nClick the Start button to begin", SwingConstants.CENTER);
 
		timeLabel = new JLabel("Current Time: ");		
 
		car1Slider = new JSlider(0, 3000);
		car1Slider.setMajorTickSpacing(1000);
		car1Slider.setPaintTicks(true);
		car1Slider.setPaintLabels(true);
 
		car2Slider = new JSlider(0, 3000);
		car2Slider.setMajorTickSpacing(1000);
		car2Slider.setPaintTicks(true);
		car2Slider.setPaintLabels(true);
 
		car3Slider = new JSlider(0, 3000);
		car3Slider.setMajorTickSpacing(1000);
		car3Slider.setPaintTicks(true);
		car3Slider.setPaintLabels(true);		
 
		//=====================================
		//JPanel's for headers, buttons, time,
		//intersections, datatable
		//=====================================
		JPanel headerPanel = new JPanel();
		headerPanel.setLayout(new GridLayout(2,1));
		headerPanel.add(header1);
		headerPanel.add(header2);
 
		JPanel buttonPanel = new JPanel();
		buttonPanel.add(startButton);
		buttonPanel.add(pauseButton);
		buttonPanel.add(stopButton);
 
		JPanel timePanel = new JPanel();
		timePanel.add(timeLabel);
		timePanel.add(currentTime);
 
		JPanel boxPanel = new JPanel();
		boxPanel.add(carBoxLabel);
		boxPanel.add(carsJComboBox);
		boxPanel.add(intersectionBoxLabel);
		boxPanel.add(intersectionJComboBox);
 
		JPanel lightPanel = new JPanel();
   		lightPanel.add(trafficLightLabel1);
		lightPanel.add(trafficLight1);
		lightPanel.add(trafficLightLabel2);
		lightPanel.add(trafficLight2);
		lightPanel.add(trafficLightLabel3);
		lightPanel.add(trafficLight3);
 
		JScrollPane scrollPane = new JScrollPane(dataTable);
		JPanel dataPanel = new JPanel();
		dataPanel.add(scrollPane);		
 
		//================================
		//add JPanels and JSliders to GUI
		//================================
		add(headerPanel);
		add(timePanel);
		add(boxPanel);
		add(buttonPanel);
		add(lightPanel);
		add(car1Slider);
		add(car2Slider);
		add(car3Slider);
		add(dataPanel);
 
		//==============================================
		//add ChangeListners and set Values to JSliders
		//==============================================
		car1Slider.addChangeListener(this);
		car1Slider.setValue(car1.getPosition());
		car2Slider.addChangeListener(this);
		car2Slider.setValue(car2.getPosition());
		car3Slider.addChangeListener(this);				
		car3Slider.setValue(car3.getPosition());
		setButtons();
 
		//=========================
		//setting JTable Viewports
		//=========================
		dataTable.setPreferredScrollableViewportSize(new Dimension(400, 300));
		dataTable.setFillsViewportHeight(true);
 
		//===================
		//run current thread
		//===================
		running = Thread.currentThread().isAlive();		
	}
 
	//==================================
	//handles all JButtons ActionEvents
	//==================================
	private void setButtons() {
 
		//====================================
		//handles "Start" buttton ActionEvent
		//====================================
		startButton.addActionListener((ActionEvent e) -> {
 
			//=================================================================
			//begin threads for cars and intersections when "Start" is clicked
			//=================================================================
			if(!simIsRunning.get()) {
				System.out.println(Thread.currentThread().getName() + " calling start");
 
				try {
					intersection1.start();
					intersection2.start();
					intersection3.start();
					car1.start();
					car2.start();
					car3.start();
					thread.start();  /**Exception thrown here
 
 
 
 
 
 
                                                               */
				}
				catch(IllegalThreadStateException itse) {
					itse.printStackTrace();;
				}
				catch(NullPointerException npe) {
					npe.printStackTrace();
				}				
			}
			simIsRunning.set(true);
		});
 
		//===================================
		//handles "Pause" button ActionEvent
		//===================================
		pauseButton.addActionListener((ActionEvent e) -> {
 
			if(simIsRunning.get()) {
 
				//=====================================================
				//loop through cars and intersections to call paused()
				//=====================================================
				for(Car i: carArray) {
					i.paused();
					System.out.println(Thread.currentThread().getName() + " calling pause");
				}
 
				//=======================================
				//for loop to interrupt sleeping threads
				//=======================================
				for(Intersection i: intersectionArray) {
					i.interrupt();
					i.paused();
				}
 
				//=========================================
				//-changes pause button text to "Continue"
				//-sets simluation running to false
				//=========================================
				pauseButton.setText("Continue");
				simIsRunning.set(false);
			} 
 
			//=============================
			//"Continue" button is clicked
			//=============================
			else {
 
				//====================================
				//for loop to resume threads for cars
				//====================================
				for(Car i:carArray) {
 
					if(i.paused.get()) {
						i.resume();
						System.out.println(Thread.currentThread().getName() + " calling resume");
					}
				}
 
				//=============================================
				//for loop to resume threads for intersections
				//=============================================
				for(Intersection i: intersectionArray) {
					i.resume();
				}
 
				//=========================================
				//-changes continue button text to "Pause"
				//-sets simluation running to true
				//=========================================
				pauseButton.setText("Pause");
				simIsRunning.set(true);
			}
		});
 
		//==================================
		//handles "Stop" button ActionEvent
		//==================================
		stopButton.addActionListener((ActionEvent e) -> {
 
			if(simIsRunning.get()) {
				System.out.println(Thread.currentThread().getName() + " calling stop");
 
				//=================================
				//for loop to stop all car threads
				//=================================
				for(Car i: carArray) {
					i.stop();
				}
 
				//==========================================
				//for loop to stop all intersection threads
				//==========================================
				for(Intersection i: intersectionArray) {
					i.stop();
				}
				simIsRunning.set(false);
			}
		});
	}
 
	//=========================================
	//checks status of the intersection. Stops
	//car threads for running the lights
	//=========================================
	private void getData() {
		if(simIsRunning.get()) {
 
			//======================================
			//switch case for intersection 1 colors
			//======================================
			switch(intersection1.getColor()) {
			case "Red":
				//=====================================
				//red light. Cars drive all the way up
				//to 1st intersection and stop at 989
				//=====================================
				for(Car i: carArray) {
 
					if(i.getPosition() > 989 && i.getPosition() < 1000) {
						i.atStopLight.set(true);
					}
				}
				break;
			case "Green":
				//==================================
				//green light. Keep driving through
				//==================================
				for(Car i:carArray) {
 					if(i.atStopLight.get()) {
						 i.resume();
					}
				}
				break;
			}
 
			//======================================
			//switch case for intersection 2 colors
			//======================================
			switch(intersection2.getColor()) {
			case "Red":
				//=====================================
				//red light. Cars drive all the way up
				//to 2nd intersection and stop at 1989
				//=====================================
				for(Car i: carArray) {
 
					if(i.getPosition() > 1989 && i.getPosition() < 2000) {
						i.atStopLight.set(true);
					}
				}
				break;
			case "Green":
				//==================================
				//green light. Keep driving through
				//==================================
				for(Car i:carArray) {
					if(i.atStopLight.get()) {
						i.resume();
					}
				}
				break;
			}
 
			//======================================
			//switch case for intersection 3 colors
			//======================================
			switch(intersection3.getColor()) {
			case "Red":
				//=====================================
				//red light. Cars drive all the way up
				//to 2nd intersection and stop at 2989
				//=====================================
				for(Car i: carArray) {
 
					if(i.getPosition() > 2989 && i.getPosition() < 3000) {
						i.atStopLight.set(true);
					}
				}
				break;
			case "Green":
				//===================================
				//green light. Keep driving through.
				//loops back to beginning of track
				//===================================
				for(Car i:carArray) {
 
					if(i.atStopLight.get()) {
						i.resume();
					}
				}
				break;
			}
		}
	}
 
	//=============================================================
	//adjusts JSlider values and car speeds as their states change
	//=============================================================
	@Override
	public void stateChanged(ChangeEvent e) {
		try {
			trafficData[0][1] = car1Slider.getValue();
			trafficData[1][1] = car2Slider.getValue();
			trafficData[2][1] = car3Slider.getValue();
 
			trafficData[0][3] = car1.getSpeed() + " km/h";
			trafficData[1][3] = car2.getSpeed() + " km/h";
			trafficData[2][3] = car3.getSpeed() + " km/h";
		}
		catch(NullPointerException npe) {
			npe.printStackTrace();
		}
 
		dataTable.repaint();		
	}
 
	//====================================
	//constantly update JSliders position
	//====================================
	@Override
	public void run() {
 
		while(running) {
 
			if(simIsRunning.get()) {
				car1Slider.setValue(car1.getPosition());
				car2Slider.setValue(car2.getPosition());
				car3Slider.setValue(car3.getPosition());
				getData();
			}
		}
 
	}
}

Time.java

/**
* Time retrieves the current time EST and formats it to display
* hours:minutes:seconds and runs it concurrently while the
* program is running using a thread
*/
 
//=========
//packages
//=========
import java.text.*;
import java.util.*;
 
//====================
//start of class time
//====================
public class Time implements Runnable {
 
	//==========
	//variables
	//==========
	private boolean running;
	private String timePattern = "hh:mm:ss a";
 
	//=========
	//invoking
	//=========
	private Date date = new Date(System.currentTimeMillis());	
	private SimpleDateFormat timeFormat = new SimpleDateFormat(timePattern);	
 
	//============
	//constructor
	//============
	public Time() {
		this.running = Thread.currentThread().isAlive();
	}
 
	//==========================================
	//retrieves the current time and returns it 
	//==========================================
	public String getTime() {
		date = new Date(System.currentTimeMillis());
		return timeFormat.format(date);
	}
 
	//========================================================
	//constantly update current time while program is running
	//========================================================
	@Override
	public void run() {
		while (running) {
			TrafficMitigation.currentTime.setText(getTime());
		}
	}
}

Intersection.java

/**
* Intersection controls the traffic lights at the 3 intersections spaced
* apart on JSlider(0, 3000) evenly at 1000 intervals. Cars can pass through
* the intersections on Green and Yellow but cant pass on Red
*/
 
 
//=========
//packages
//=========
import java.awt.*;
import javax.swing.*;
import java.util.concurrent.atomic.*;
 
//============================
//start of class Intersection
//============================
public class Intersection implements Runnable {
 
	//======
	//array
	//======
	private final String[] COLORS = {"Green", "Yellow", "Red"};
 
	//==========
	//variables
	//==========	
	private JLabel jLabel;
	private int i = 0;
	private Thread thread;	
	private String currentLight = COLORS[i];
	private String threadName;
 
	//=========
	//invoking
	//=========
	private static final AtomicBoolean running = new AtomicBoolean(false);
	public static final AtomicBoolean paused = new AtomicBoolean(false);
 
	//============
	//constructor
	//============
	public Intersection(String name, JLabel j) {
		this.threadName = name;
		this.jLabel = j;
		System.out.println("Creating " + threadName);
	}
 
	//=================================================
	//synchornizes getting traffic light colors: G,Y,R
	//=================================================
	public synchronized String getColor() {
		this.currentLight = COLORS[i];
		return this.currentLight;
	}
 
	//============================
	//pauses and displays threads
	//============================
	public void paused() {
		paused.set(true);
		System.out.println("Pausing " + threadName);
	}
 
	//===========================================
	//synchronizes and displays resuming threads
	//===========================================
	public synchronized void resume() {
		paused.set(false);
		notify();
		System.out.println("Resuming " + threadName);
	}
 
	//============================
	//starts and displays threads
	//============================
	public void start() {
		System.out.println("Starting " + threadName);
		if(thread == null) {
			thread = new Thread(this, threadName);
			thread.start();
		}
	}
 
	//=============================================
	//stops and displays threads using interrupt()
	//=============================================
	public void stop() {
		thread.interrupt();
		running.set(false);
		System.out.println("Stopping " + threadName);
	}
 
	//===================
	//interrupts threads
	//===================
	public void interrupt() {
		thread.interrupt();
	}
 
	//========================
	//display running threads
	//========================
	@Override
	public void run() {
		System.out.println("Running " + threadName);
		running.set(true);
 
		//========================
		//while thread is running
		//========================
		while(running.get()) {
 
			//===================
			//try to synchronize
			//===================
			try {
				synchronized(this) {
 
					//=======================
					//while thread is paused
					//=======================
					while(paused.get()) {
						System.out.println(threadName + " waiting");
						wait();
					}
				}
 
				//==========================================
				//switch case for changing the color of the
				//lights and putting threads to sleep
				//==========================================
				switch (getColor()) {
				case "Green":
					//==========================================
					//green light. goes to sleep for 10 seconds
					//increments 'i' so the next light color is
					//yellow
					//==========================================
					jLabel.setForeground(Color.GREEN.darker());
					jLabel.setText(getColor());
					Thread.sleep(10000);
					i++;
					break;
				case "Yellow":
					//==========================================
					//yellow light. Goes to sleep for 5 seconds
					//increments 'i' so the next light color is
					//red
					//==========================================
					jLabel.setForeground(Color.YELLOW.darker());
					jLabel.setText(getColor());
					Thread.sleep(5000);
					i++;
					break;
				case "Red":
					//=======================================
					//red light. Goes to sleep for 5 seconds
					//sets 'i' back to zero so the next 
					//light color is green
					//=======================================
					jLabel.setForeground(Color.RED.darker());
					jLabel.setText(getColor());
					Thread.sleep(5000);
					i = 0;
					break;
				default:
					break;
				}
			} 
			catch(NullPointerException npe) {
				npe.printStackTrace();
			}
			catch(InterruptedException ex) {
				paused.set(true);
			}
		}
	}
}

Car.java

/**
* Car controls the speed of the cars, the x-position and thread
* starting, pausing, resuming and stopping 
*/
 
//=========
//packages
//=========
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
 
//===================
//start of class Car
//===================
public class Car implements Runnable {
 
	//==========
	//variables
	//==========
	private int xPosition;
	private int speed = 0;
 
	private String threadName = "";
 
	public Thread thread;
 
	//=========
	//invoking
	//=========
	private final AtomicBoolean running = new AtomicBoolean(false);
 
	public final AtomicBoolean atStopLight = new AtomicBoolean(false);
	public final AtomicBoolean paused = new AtomicBoolean(false);
 
	//============
	//constructor
	//============
	public Car(String name, int max, int min) {
		this.threadName = name;
		this.xPosition = ThreadLocalRandom.current().nextInt(min, max);
		System.out.println("Creating " + threadName);
	}
 
	//=====================================
	//determines position of the cars at x
	//=====================================
	public synchronized int getPosition() {
		return xPosition;
	}
 
	//========================================
	//calculates the speed of the cars in kph
	//========================================
	public int getSpeed() {
 
		if(running.get()) {
 
			if(atStopLight.get()) {
				speed = 0;
			}
			else {
				speed = 3 * 60;
			}
		} 
		else
			speed = 0;
		return speed;
	}
 
	//==========================
	//displays threads starting
	//==========================
	public void start() {
		System.out.println("Starting " + threadName);
 
		if(thread == null) {
			thread = new Thread(this, threadName);
			thread.start();
		}
	}
 
	//==========================
	//displays threads stopping
	//==========================
	public void stop() {
		thread.interrupt();
		running.set(false);
		System.out.println("Stopping " + threadName);
	}
 
	//=========================
	//displays threads pausing
	//=========================
	public void paused() {
		paused.set(true);
		System.out.println("Paused " + threadName);
	}
 
	//==========================
	//displays threads resuming
	//==========================
	public synchronized void resume() {
 
		if(paused.get() || atStopLight.get()) {
			paused.set(false);
			atStopLight.set(false);
			notify();
			System.out.println("Resuming " + threadName);
		}
	}
 
	//=========================
	//displays threads running
	//=========================
	@Override
	public void run() {
		System.out.println("Running " + threadName);
		running.set(true);
 
		//===============================
		//while AtomicBoolean is running
		//===============================
		while(running.get()) {
			try {
 
				//=============================
				//while cars x position < 3000
				//=============================
				while(xPosition < 3000) {
					synchronized(this) {
 
						//==============================
						//while paused or at stop light
						//==============================
						while(paused.get() || atStopLight.get()) {
							System.out.println(threadName + " waiting");
							wait();
						}
					}
 
					//=======================
					//Check if still running
					//=======================
					if(running.get()) {
						Thread.sleep(100);
						xPosition += 5;
					}
				}
				xPosition = 0;
			} 
			catch(InterruptedException ie) {
				return;
			}
		}
	}
}

[Norm]

Have you read the API doc for the start method? It says:

Throws:
IllegalThreadStateException - if the thread was already started.

[EasyE]

My program runs and threads work, what is ThreadLocalRandom good for? Still learning Threads and Multithreading

[Norm]

My program runs and threads work,

Have you fixed your problem? What did you change?