[Fix] Java - Exception in thread main java.lang.IllegalThreadStateException


Stack trace:
/Library/Java/JavaVirtualMachines/zulu-11.jdk/Contents/Home/bin/java 
-javaagent:/Applications/IntelliJ 
IDEA CE.app/Contents/lib/idea_rt.jar=49386:/Applications/IntelliJ 
IDEA CE.app/Contents/bin 
-Dfile.encoding=UTF-8 
-classpath /Users/code2care/IdeaProjects/multi-tasking/out/production/multi-tasking 
MyThread

Exception in thread "main" java.lang.IllegalThreadStateException
	at java.base/java.lang.Thread.start(Thread.java:789)
	at MyThread.main(MyThread.java:8)
This is Main Thread
This is my Thread

Process finished with exit code 1

✏️ IllegalThreadStateException is thrown to indicate that a thread is not in an appropriate state for the requested operation.

Example, you will see java.lang.IllegalThreadStateException when you are using Multi-Threading in your Java program and you start the same thread more than one!

Example:
/**
 * Java Code Example: code2care.org
 */
public class MyThread extends Thread {

    public static void main(String[] args) {

        MyThread thread = new MyThread();
        thread.start();
        System.out.println("This is Main Thread");
        thread.start(); //IllegalThreadStateException

    }

    @Override
    public void run() {
         System.out.println("This is my Thread");
    }

}
Fix java.lang.IllegalThreadStateException Error
Fix:

The above code can be fixed by making sure that once the thread is not started multiple times.

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