Reset mutable class fields

Say I have a class with some mutable fields:

public class Test
{
    private boolean isCorrect;
    private String userId;

    public void run() {...}
    
    // more methods
}

The run() method will be modifying these fields. My issues is that the caller of this class might call run() any number of times, and for this reason I should be re-setting the fields back to null.

My question is, what is the best practice for this scenario? Should I reset the fields every time the method is called?

public void run()
{
    isCorrect = null;
    userId = null;
    // do stuff
}

Or is there a cleaner/smarter approach to this?

The simple answer is use local variables. The OP has clarified in the comments that run calls other methods on the same instance that expect to use these variable too.

The class should be split. The run method should create an object containing the fields and call methods on that.

public class Test {

    public void run() {
         TestImpl impl = new TestImpl();
         impl.run();
    }
    
    // more methods
}
class TestImpl {
    private boolean isCorrect;
    private String userId;

    public void run() {...}
    
    // more methods
}

You could make the new class a nested class, though that does cause excessive indention. An inner class would also have direct access to any longer lived variables of Test. An anonymous inner class (or, more obscurely, a local class) would be even more convenient but indented.

I would do it this way. Using an exception. So anyone who dares to use run() twice gets kicked out.

package test;

import com.sun.jdi.IncompatibleThreadStateException;

public class Test{
	private boolean isRunning = false;
	
	public void run() throws IncompatibleThreadStateException{
		if(this.isRunning) {
			throw new IncompatibleThreadStateException();
		}
		else {
			this.isRunning = true;
		}
	}
	
	public static void main(String[] args) {
		
	}
}