Thinking in Java Fourth Edition Bruce Eckel Chapter 4 Exercise 11

class WebBank
{
    boolean loggedIn = false;
    WebBank(boolean logStatus)
    {
        loggedIn = logStatus;
    }
    void logOut()
    {
        loggedIn = false;
    }
    protected void finalize()
    {
        if(loggedIn)
            System.out.println("Error: still logged in");
        // Normally, you'll also call the base-class version:
        // super.finalize();
    }
}

public class BankTest
{
    public static void main(String[] args)
    {
        WebBank bank1 = new WebBank(true);
        WebBank bank2 = new WebBank(true);
        new WebBank(true);
        // Proper cleanup: log out of bank1 before going home:
        bank1.logOut();
        // Forget to logout of bank2 and unnamed new bank
        // Attempts to finalize any missed banks:
        System.out.println("Try 1: ");
        System.runFinalization();
        System.out.println("Try 2: ");  
        Runtime.getRuntime().runFinalization();
        System.out.println("Try 3: ");
        System.gc();
        System.out.println("Try 4: ");
        // using deprecated since 1.1 method:
        System.runFinalizersOnExit(true);      
    }  
}