I\'m getting error ArithmeticOperation.java:15: error: invalid method declaratio

Question

I'm getting error
ArithmeticOperation.java:15: error: invalid method declaration; return type required
public arithmeticOperationJOptionPane() {
^

code :

import javax.swing.*;
//Java Extension Package
import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane;

public class ArithmeticOperation extends JFrame {


private JButton buttons[];
private String operation[] = {"Addition [+]","Subtraction [-]","Multiplication [x]","Division [/]"};


public arithmeticOperationJOptionPane() {


super("Arithmetic Operation using JOptionPane");


setSize(500,500);


setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


buttons = new JButton[4];


Container pane = getContentPane();
setContentPane(pane);


GridLayout grid = new GridLayout(2,2);
pane.setLayout(grid);


for(int count=0; count<buttons.length; count++) {
buttons[count] = new JButton(operation[count]);
pane.add(buttons[count]);
}

buttons[0].addActionListener(

new ActionListener() {


public void actionPerformed(ActionEvent event) {
try {


String input1, input2;
int num1, num2, result;


input1 = JOptionPane.showInputDialog("Please Input First Number: ");
input2 = JOptionPane.showInputDialog("Please Input Second Number: ");


num1 = Integer.parseInt(input1);
num2 = Integer.parseInt(input2);


result = num1 + num2;


JOptionPane.showMessageDialog(null,result,"Result:",JOptionPane.INFORMATION_MESSAGE);
} catch (NumberFormatException e){ //Catch the error if the user inputs a non-integer value


JOptionPane.showMessageDialog(null, "Please Input a Integer","Error",JOptionPane.ERROR_MESSAGE);
}
}
}
);


buttons[1].addActionListener(
new ActionListener() {


public void actionPerformed(ActionEvent event) {
try {
String input1, input2;
int num1, num2, result;

input1 = JOptionPane.showInputDialog("Please Input First Number: ");
input2 = JOptionPane.showInputDialog("Please Input Second Number: ");

num1 = Integer.parseInt(input1);
num2 = Integer.parseInt(input2);

result = num1 - num2;

JOptionPane.showMessageDialog(null,result,"Result:",JOptionPane.INFORMATION_MESSAGE);
} catch (NumberFormatException e){
JOptionPane.showMessageDialog(null, "Please Input a Integer","Error",JOptionPane.ERROR_MESSAGE);

}
}
}
);

//Implemeting Even-Listener on JButton button[2] which is multiplication
buttons[2].addActionListener(
new ActionListener() {

//Handle JButton event if it is clicked
public void actionPerformed(ActionEvent event) {
try {
String input1, input2;
int num1, num2, result;

input1 = JOptionPane.showInputDialog("Please Input First Number: ");
input2 = JOptionPane.showInputDialog("Please Input Second Number: ");

num1 = Integer.parseInt(input1);
num2 = Integer.parseInt(input2);

result = num1 * num2;

JOptionPane.showMessageDialog(null,result,"Result:",JOptionPane.INFORMATION_MESSAGE);
} catch (NumberFormatException e){
JOptionPane.showMessageDialog(null, "Please Input a Integer","Error",JOptionPane.ERROR_MESSAGE);

}
}
}
);

//Implemeting Even-Listener on JButton button[3] which is division
buttons[3].addActionListener(
new ActionListener() {

//Handle JButton event if it is clicked
public void actionPerformed(ActionEvent event) {
try {
String input1, input2;
int num1, num2, result;

input1 = JOptionPane.showInputDialog("Please Input First Number: ");
input2 = JOptionPane.showInputDialog("Please Input Second Number: ");

num1 = Integer.parseInt(input1);
num2 = Integer.parseInt(input2);

result = num1 / num2;

JOptionPane.showMessageDialog(null,result,"Result:",JOptionPane.INFORMATION_MESSAGE);
} catch (NumberFormatException e){
JOptionPane.showMessageDialog(null, "Please Input a Integer","Error",JOptionPane.ERROR_MESSAGE);

}
}
}
);

buttons[0].setMnemonic('A');
buttons[1].setMnemonic('S');
buttons[2].setMnemonic('M');
buttons[3].setMnemonic('D');

/**Set all the Components Visible.
* If it is set to "false", the components in the container will not be visible.
*/
setVisible(true);
setResizable(false); //Fix window height and width
}

//Main Method
public static void main (String[] args) {
arithmeticOperationJOptionPane pjtf = new arithmeticOperationJOptionPane();
}
}

Explanation / Answer

Every method except constructors must have a return type or void specified; if not, this error will arise: max(int i, int j) { ... } The error frequently occurs because it is easy to misspell the name of a constructor; the compiler then thinks that it is a normal method without a return type: class MyClass { MyClass(int i) { ... } Myclass(int i, int j) { ... } // Error because of the lowercase c }

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