About java final access modifier

Question

I am making Java Swing application. i made check box item, then when i was calling show.isSelected() method, i got an error that you have to make show final, then i made it final and the error was gone, the error was in the 9th line, but i did not understand that what was the reason for making show final and what final does with show ?

    final JCheckBoxMenuItem show=new JCheckBoxMenuItem("Show");
    show.setSelected(true);
    show.addActionListener(new ActionListener(){

        public void actionPerformed(ActionEvent arg0) 
        {

            formpanel.setVisible(show.isSelected()); ////// giving error without final

        }

    });

Duplicate: https://stackoverflow.com/questions/4732544/why-are-only-final-variables-accessible-in-anonymous-class — Steve Smith, Aug 15 '17 at 11:55
This error shows you're using an old version of Java. Java 8 automatically detects if references are effectively final. — JB Nizet, Aug 15 '17 at 11:55
If you use Java 8, you don't have to explicitly declare it `final`. Effectively final is enough, i.e. you don't reassign the variable anywhere. — bcsb1001, Aug 15 '17 at 11:55

score 1 · Accepted Answer · answered Aug 15 '17 at 11:54

1

The final keyword prevents you from reassigning reference show so the compiler can safely copy its value into new anonymous object created by new ActionListener statement.

answered Aug 15 '17 at 11:54

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could you please give me an example ?? – Taimoor Khan Aug 15 '17 at 12:07

About java final access modifier

1 Answers1