Thread: Can anyone help me with this java problem? [Java]

Exception in thread "main" java.lang.ClassCastException: calculator.Calculator cannot be cast to java.awt.event.ActionListener
at calculator.Calculator.<init>(Calculator.java:142)
at calculator.Main_calculator.main(Main_calculator.ja va:7)

Code:
package calculator;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.border.Border;

public class Calculator {

JFrame frame = new JFrame();
JPanel panel = new JPanel();
JTextArea textarea = new JTextArea(2,10);
JButton button1 = new JButton ();
JButton button2 = new JButton ();
JButton button3 = new JButton ();
JButton button4 = new JButton ();
JButton button5 = new JButton ();
JButton button6 = new JButton ();
JButton button7 = new JButton ();
JButton button8 = new JButton ();
JButton button9 = new JButton ();
JButton button0 = new JButton ();

JButton buttondot = new JButton ();
JButton buttonequal = new JButton ();
JButton buttonadd = new JButton ();
JButton buttonsub = new JButton ();
JButton buttonmul = new JButton ();
JButton buttondiv = new JButton ();
JButton buttonclear = new JButton ();

double number1,number2,resoult;
int addc=0,mulc=0,divc=0,subc=0;

public Calculator () {

frame.setSize(340,450);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS E);
frame.setVisible(true);
frame.setTitle("Calcolatrice di Paolo");

//frame.setResizable(false);

frame.add(panel);
panel.setBackground(Color.white);
Border border = BorderFactory.createLineBorder(Color.RED,4);

panel.add(textarea);

textarea.setBackground(Color.black);
Border tborder = BorderFactory.createLineBorder(Color.blue,3);
textarea.setBorder(tborder);
Font font = new Font("Arial",Font.BOLD,33);
textarea.setFont(font);
textarea.setForeground(Color.WHITE);

textarea.setPreferredSize(new Dimension (2,10));
textarea.setLineWrap(true);

//lista numeri
button1.setPreferredSize(new Dimension(100,50));
button1.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton1.png"));

button2.setPreferredSize(new Dimension(50,50));
button2.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton2.png"));

button3.setPreferredSize(new Dimension(50,50));
button3.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton3.png"));

button4.setPreferredSize(new Dimension(50,50));
button4.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton4.png"));

button5.setPreferredSize(new Dimension(50,50));
button5.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton5.png"));

button6.setPreferredSize(new Dimension(50,50));
button6.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton6.png"));

button7.setPreferredSize(new Dimension(50,50));
button7.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton7.png"));

button8.setPreferredSize(new Dimension(50,50));
button8.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton8.png"));

button9.setPreferredSize(new Dimension(50,50));
button9.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton9.png"));

button0.setPreferredSize(new Dimension(50,50));
button0.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\b utton0.png"));

//lista segni

buttondot.setPreferredSize(new Dimension(50,50));
buttondot.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\d ot.png"));

buttonmul.setPreferredSize(new Dimension(50,50));
buttonmul.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\m ul.png"));

buttondiv.setPreferredSize(new Dimension(50,50));
buttondiv.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\d iv.png"));

buttonadd.setPreferredSize(new Dimension(50,50));
buttonadd.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\p lus.png"));

buttonsub.setPreferredSize(new Dimension(50,50));
buttonsub.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\s ub.png"));

buttonequal.setPreferredSize(new Dimension(50,50));
buttonequal.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\e qual.png"));

buttonclear.setPreferredSize(new Dimension(50,50));
buttonclear.setIcon(new ImageIcon("C:\\Users\\Utente\\Desktop\\immagini\\c lear.png"));


panel.add(button1);
panel.add(button2);
panel.add(button3);
panel.add(button4);
panel.add(button5);
panel.add(button6);
panel.add(button7);
panel.add(button8);
panel.add(button9);
panel.add(button0);
panel.add(buttondot);
panel.add(buttondiv);
panel.add(buttonsub);
panel.add(buttonmul);
panel.add(buttonadd);
panel.add(buttonequal);
panel.add(buttonclear);

button1.addActionListener((ActionListener) this);
button2.addActionListener((ActionListener) this);
button3.addActionListener((ActionListener) this);
button4.addActionListener((ActionListener) this);
button5.addActionListener((ActionListener) this);
button6.addActionListener((ActionListener) this);
button7.addActionListener((ActionListener) this);
button8.addActionListener((ActionListener) this);
button9.addActionListener((ActionListener) this);
button0.addActionListener((ActionListener) this);
buttondot.addActionListener((ActionListener) this);
buttonadd.addActionListener((ActionListener) this);
buttonsub.addActionListener((ActionListener) this);
buttondiv.addActionListener((ActionListener) this);
buttonmul.addActionListener((ActionListener) this);
buttonclear.addActionListener((ActionListener) this);
buttonequal.addActionListener((ActionListener) this);

}




public void actionPerformed (ActionEvent e) {

Object source = e.getSource();
number1=0.0;
number2=0.0;
textarea.setText("");


if (source==button1) {
textarea.append("1");
}
if(source==button2){
textarea.append("2");
}
if(source==button2){
textarea.append("2");
}
if(source==button3){
textarea.append("3");
}
if(source==button4){
textarea.append("4");
}
if(source==button5){
textarea.append("5");
}
if(source==button6){
textarea.append("6");
}
if(source==button7){
textarea.append("7");
}
if(source==button8){
textarea.append("8");
}
if(source==button9){
textarea.append("9");
}
if(source==button0){
textarea.append("0");
}
if(source==buttondot){
textarea.append(".");
}


if(source==buttonadd){
number1=number_reader();
textarea.setText("+");
addc=1;
divc=0;
mulc=0;
subc=0;
}
if(source==buttondiv){
number1=number_reader();
textarea.setText("/");
addc=0;
divc=1;
mulc=0;
subc=0;

}
if(source==buttonmul){
number1=number_reader();
textarea.setText("*");
addc=0;
divc=0;
mulc=1;
subc=0;

}
if(source==buttonsub){
number1=number_reader();
textarea.setText("-");
addc=0;
divc=0;
mulc=0;
subc=1;

}
if(source==buttonequal){
number1=number_reader();
if(addc>0) {
resoult=number1+number2;
textarea.setText(Double.toString(resoult));
}
if(subc>0) {
resoult=number1-number2;
textarea.setText(Double.toString(resoult));
}
if(mulc>0) {
resoult=number1*number2;
textarea.setText(Double.toString(resoult));
}
if(divc>0) {
resoult=number1/number2;
textarea.setText(Double.toString(resoult));
}

}





}

public double number_reader() {
double num1;
String s;
s=textarea.getText();
num1=Double.valueOf(s);
return num1;
}
}

-------------------------Main:
package calculator;

public class Main_calculator {

public static void main(String[] args) {

Calculator cal = new Calculator ();

}

}

It's because your Calculator class does not implement ActionListener. If you add the @Override annotation to the actionPerformed function (a good habit for all overridden functions), you'll get a compiler error letting you know it's not overriding anything:

@Override  // <- Error: does not override or implement a method from a supertype
public void actionPerformed (ActionEvent e) {
 
}

So tag your class as implementing ActionListener, then actionPerformed is an override as expected:

public class Calculator implements ActionListener {
 
}

With this, the error on the @Override annotation, and the ClassCastException, should both go away.