为什么我得到的Display不是抽象的并且没有覆盖Display中的抽象方法actionPerformed（）？

Question

I've been following some tutorials on making word processors and have followed every step however I got stuck when I ran into this error:

Display is not abstract and does not orverride abstract method actionPerformed() in Display

the code I use for Display:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTextPane;


public class Display extends JPanel implements ActionListener {
    private JTextPane textArea;
    private JButton saveButton;
    private JComboBox colorCombo;
    private JComboBox fontCombo;
    private JLabel processorLabel;
    private JSlider fontSize;

    //addAction Listener methods.
public void actionperformed(ActionEvent e){

}


// create arrays.
    String[] colorItems = {"red", "Blue", "Green", "Purple", "Orange", "Black"};
    String[] fontItems = {"Monospaced", "Serif", "San Serif"};
//constructor.
    public Display(){
        init(); // Display calls for init.
    }
    public void init(){ // where buttons and labels coding go.
     //construct components.
       textArea = new JTextPane();
       saveButton = new JButton("save");
       colorCombo = new JComboBox(colorItems);
       fontCombo = new JComboBox(fontItems);
       processorLabel = new JLabel("Mo's W.P");
       fontSize = new JSlider(10, 30);


       //Slider work.
       fontSize.setOrientation(JSlider.HORIZONTAL);
       fontSize.setMinorTickSpacing(1);
       fontSize.setMajorTickSpacing(5);
       fontSize.setPaintTicks(true); //displays the text.
       fontSize.setPaintLabels(true); //displays paint pop ups

       // Make text area presentable.
       textArea.setBackground(Color.LIGHT_GRAY);
       //textArea.setForeground(color);

       //adjust size and layout.
       setPreferredSize(new Dimension(817, 473));
       setLayout(null);

       //add components.
       add(textArea);
       add(saveButton);
       add(colorCombo);
       add(fontCombo);
       add(processorLabel);
       add(fontSize);

       textArea.setBounds(10, 10, 650, 450);
       saveButton.setBounds(670, 315, 140, 35);
       colorCombo.setBounds(670, 205, 140, 53);
       fontCombo.setBounds(670, 150, 140, 35);
       processorLabel.setBounds(670, 20, 140, 35);
       fontSize.setBounds(670, 95, 140, 40);

       //add action listeners. 
       saveButton.addActionListener(this);
       colorCombo.addActionListener(this);
       fontCombo.addActionListener(this);

    }


}

Answer 1

The identifiers in Java are case-sensitive. In your code there is a method named actionperformed , but actionPerformed is expected to be implemented.

It's also good practice to use @Override annotation if our method overrides another method or implements abstract method declaration (note: all method declarations in interfaces are implicit abstract). This allows compiler to perform additional check if method really overrides another and produces error if it does not.

Answer 2

Your class implements the interface ActionListener , but doesn't implement the contractual requirements of the interface

You must implement the actionPerformed method as described by the ActionListener interface

See How to write a ActionListener for more details