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Thread: Action Listener Error

  1. #1
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    Default Action Listener Error

    I get this error:
    LBMPG.java:51: LBMPG.CalcButtonListener is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener
    private class CalcButtonListener implements ActionListener
    ^

    This is my code:
    import javax.swing.*;
    import java.awt.event.*;
     
    public class LBMPG extends JFrame
    {
    	private JPanel panel;
    	private JLabel gallonLabel;
    	private JLabel milesLabel;
    	private JTextField gallonsTextField;
    	private JTextField milesTextField;
    	private JButton calcButton;
    	private final int WINDOW_WIDTH = 400;
    	private final int WINDOW_HEIGHT = 100;
     
     
     
    public LBMPG()
    {
    	setTitle("Miles per Gallon");
    	setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
    	setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    	buildPanel();
    	add(panel);
    	setVisible(true);
    }
     
    private void buildPanel()
    {
    	gallonLabel = new JLabel("Enter the amount of gallons your tank holds:");
    	gallonsTextField = new JTextField(2);
    	milesLabel = new JLabel("Enter the amount of miles you can go on a full tank:");
    	milesTextField = new JTextField(3);
    	calcButton = new JButton("Calculate MPG");
    	calcButton.addActionListener(new CalcButtonListener());
     
    	panel = new JPanel();
    	panel.add(gallonLabel);
    	panel.add(gallonsTextField);
    	panel.add(milesLabel);
    	panel.add(milesTextField);
    	panel.add(calcButton);
    }
     
    private class CalcButtonListener implements ActionListener
    {
    public void actionPerfmored(ActionEvent e)
    {
    	String input;
    	double mpg;
    	double gallons;
    	double miles;
     
    	input = gallonsTextField.getText();
    	gallons = Double.parseDouble(input);
    	input = milesTextField.getText();
    	miles = Double.parseDouble(input);
     
    	mpg = miles / gallons;
     
    	JOptionPane.showMessageDialog(null, "Your car gets approximately " + mpg + " miles per gallon.");
     
    }
    }
    }

    I don't understand it. I've looked up things to fix it, but they didn't work. It's also weird because I pretty much followed another code to get the basic outline, and then changed everything to fit this scenario.


  2. #2
    Administrator copeg's Avatar
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    Default Re: Action Listener Error

    java is very sensitive when it comes to spelling. In other words, actionPerfmored != actionPerformed
    The @Override annotation helps track these problems, and will indicate that a method does not override or implement a super class method or interface.

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