Java Method Call Expected

This is a java program with two buttons used to change an integer value and display it. However in IntelliJIDEA the two lines with

increase.addActionListener(incListener()); decrease.addActionListener(decListener()); 

keep displaying errors 'Method call expected'.

I am not sure what to do to fix this.

Any help will be greatly appreciated

Thanks

Note: the full code is attached below.

import javax.swing.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; public class Main extends JDialog { public JPanel contentPane; public JButton decrease; public JButton increase; public JLabel label; public int number; public Main() { setContentPane(contentPane); setModal(true); increase = new JButton(); decrease = new JButton(); increase.addActionListener(incListener()); decrease.addActionListener(decListener()); number = 50; label = new JLabel(); } public class incListener implements ActionListener { public void actionPerformed (ActionEvent event) { number++; label.setText("" + number); } } public class decListener implements ActionListener { public void actionPerformed (ActionEvent event) { number--; label.setText("" + number); } } public static void main(String[] args) { Main dialog = new Main(); dialog.pack(); dialog.setVisible(true); System.exit(0); } } 

7 Answers

incListener and declListener are classes, not methods.

Try

increase.addActionListener(new incListener()); 

btw, rename your classes names to make them start with an uppercase

It's simple: use new incListener() instead of incListener(). The later is trying to call a method named incListener, the former creates an object from the class incListener, which is what we want.

incListener and decListener are a classes but not a methods, so you must call new to use them, try this:

increase.addActionListener(new incListener()); decrease.addActionListener(new decListener());

sorry for my bad english

substitute the lines with

increase.addActionListener( new incListener()); decrease.addActionListener( new decListener()); 

Make these changes:

 public Main() { contentPane = new JPanel(); setContentPane(contentPane); setModal(true); increase = new JButton("inc"); decrease = new JButton("dec"); contentPane.add(increase); contentPane.add(decrease); increase.addActionListener(new incListener()); decrease.addActionListener(new decListener()); number = 50; label = new JLabel(number+""); contentPane.add(label); } 

It's sad but I had to Google this same error... I was staring at a method that returned a class. I left off the new operator.

return <class>(<parameters>) vs return new <class>(<parameters>)

Whenever a string object is created using new operator a new object is created which is what your program is looking for. The following link is useful in learning about the difference between a string and a new string. What is the difference between "text" and new String("text")?

ncG1vNJzZmirpJawrLvVnqmfpJ%2Bse6S7zGiorp2jqbawutJoaG9sYW1%2Ben%2BOo5ivmV2isrW0zp1knJmcoXqmxM%2Bemq2dlA%3D%3D