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Implement a simple calculator (detailed comments on JAVA code)



 import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.text.NumberFormat;//Keep decimals

public class SimpleCalculation extends JFrame{

    Frame frame = new JFrame();

    Frame MistakeWindons = new JFrame();

    private JButton SumBtn = new JButton("SUM");

    private JButton SubBtn = new JButton("SUB");

    private JButton MulBtn = new JButton("MUL");

    private JButton DivBtn = new JButton("DIV");

    private JButton Reset = new JButton("Reset");


    private JTextField FristCount = new JTextField(5);

    private JTextField SecondCount = new JTextField(5);

    private JTextField Result = new JTextField(10);

    private Label Design = new Label("Design by CodingPush");

    private Font Ft = new Font("Helvetica", Font.BOLD, 18);//Set font

    public SimpleCalculation() {

        frame.setResizable(false);//Set to not maximize

        frame.setTitle("Simple calculator");

        frame.setLocation(600, 400);//Set window position

        frame.setSize(300, 180);//Set window size

        frame.setLayout(null);

        frame.setVisible(true);

        frame.add(FristCount);

        FristCount.setBounds(10, 10, 60, 20);

        frame.add(SecondCount);

        SecondCount.setBounds(90, 10, 60, 20);

        frame.add(new Label("=")).setBounds(160, 10, 20, 20);

        frame.add(Result);

        Result.setBounds(180, 10, 100, 20);

        frame.add(Design);

        Design.setBounds(60, 40, 200, 30);

        frame.add(SumBtn);

        SumBtn.setBounds(5, 80, 70, 30);

        frame.add(SubBtn);

        SubBtn.setBounds(75, 80, 70, 30);

        frame.add(MulBtn);

        MulBtn.setBounds(145, 80, 70, 30);

        frame.add(DivBtn);

        DivBtn.setBounds(215, 80, 70, 30);

        frame.add(Reset);

        Reset.setBounds(215,110,70,30);

        Design.setFont(Ft);

        MyActionListen();

    }

        private void MyActionListen(){//Event handler

        SumBtn.addActionListener(new ActionListener() {

            @Override

            public void actionPerformed(ActionEvent e) {

                try {//Exception handling, if the input is not a number, it will prompt an input error

                    String text0 = FristCount.getText();//Convert JTextFiled to String

                    String text1 = SecondCount.getText();

                    double a = Double.valueOf(text0);//Convert String type to double

                    double b = Double.valueOf(text1);

                    Result.setText(a + b + "");

                }

                catch (Exception e1){

                    MistakeWindons.setResizable(false);

                    MistakeWindons.setLayout(null);

                    MistakeWindons.setTitle("Wrong Warning!");

                    MistakeWindons.setSize(200,100);

                    MistakeWindons.setLocation(550,550);

                    JLabel Mistake = new JLabel("Wrong Input!!!");

                    //Mistake.setFont(Ft);

                    Mistake.setBounds(50,20,100,20);

                    MistakeWindons.add(Mistake);

                    MistakeWindons.setVisible(true);

                }

                }

        });

            SubBtn.addActionListener(new ActionListener() {

                @Override

                public void actionPerformed(ActionEvent e) {

                    try {

                        String text0 = FristCount.getText();//Convert JTextFiled to String

                        String text1 = SecondCount.getText();

                        double a = Double.valueOf(text0);//Convert String type to double

                        double b = Double.valueOf(text1);

                        Result.setText(a - b + "");

                    }

                    catch (Exception e1){

                        MistakeWindons.setResizable(false);

                        MistakeWindons.setLayout(null);

                        MistakeWindons.setTitle("Wrong Warning!");

                        MistakeWindons.setSize(200,100);

                        MistakeWindons.setLocation(550,550);

                        JLabel Mistake = new JLabel("Wrong Input!!!");

                        //Mistake.setFont(Ft);

                        Mistake.setBounds(50,20,100,20);

                        MistakeWindons.add(Mistake);

                        MistakeWindons.setVisible(true);

                    }

                }

            });

            MulBtn.addActionListener(new ActionListener() {

                @Override

                public void actionPerformed(ActionEvent e) {

                    try {

                        String text0 = FristCount.getText();//Convert JTextFiled to String

                        String text1 = SecondCount.getText();

                        double a = Double.valueOf(text0);//Convert String type to double

                        double b = Double.valueOf(text1);

                        Result.setText(a * b + "");

                    }

                    catch (Exception e1){

                        MistakeWindons.setResizable(false);

                        MistakeWindons.setLayout(null);

                        MistakeWindons.setTitle("Wrong Warning!");

                        MistakeWindons.setSize(200,100);

                        MistakeWindons.setLocation(550,550);

                        JLabel Mistake = new JLabel("Wrong Input!!!");

                        Mistake.setBounds(50,20,100,20);

                        MistakeWindons.add(Mistake);

                        MistakeWindons.setVisible(true);

                    }

                }

            });

            DivBtn.addActionListener(new ActionListener() {

                @Override

                public void actionPerformed(ActionEvent e) {

                    try {

                        String text0 = FristCount.getText();//Convert JTextFiled to String

                        String text1 = SecondCount.getText();

                        double a = Double.valueOf(text0);//Convert String type to double

                        double b = Double.valueOf(text1);

                        Result.setText(a / b + "");

                        double c = a/b;

                        NumberFormat Nf = NumberFormat.getNumberInstance();//Keep decimals

                        Nf.setMaximumFractionDigits(6);

                        Result.setText(Nf.format(c));

                    }

                    catch (Exception e1){

                        MistakeWindons.setResizable(false);

                        MistakeWindons.setLayout(null);

                        MistakeWindons.setTitle("Wrong Warning!");

                        MistakeWindons.setSize(200,100);

                        MistakeWindons.setLocation(550,550);

                        JLabel Mistake = new JLabel("Wrong Input!!!");

                        //Mistake.setFont(Ft);

                        Mistake.setBounds(50,20,100,20);

                        MistakeWindons.add(Mistake);

                        MistakeWindons.setVisible(true);

                    }

                }

            });

        Reset.addActionListener(new ActionListener() {

            @Override

            public void actionPerformed(ActionEvent e) {

                FristCount.setText("");

                SecondCount.setText("");

                Result.setText("");

            }

        });

    }

}

class Text{

    public static void main(String[] args){

        SimpleCalculation simpleCalculation = new SimpleCalculation();

    }

}


There is a problem that has not been considered. 0 cannot be used as a divisor.

You can modify the exception handling under the DIV button. Just add 0 as a divisor. You can try to implement it yourself.

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