Basic Java Code Examples for Beginners

import java.util.Scanner;

           public class MyClass

           public static void main(String[] args)

          Maths math = new Maths();

          Scanner userinput = new Scanner(System.in);

          System.out.println("Welcome to Java Calculator");

          System.out.println("===========================");

          System.out.print("Enter First Number:");

          int num1 = userinput.nextInt();

System.out.print("Enter Second Number:");

           int num2= userinput.nextInt();

           System.out.print("Enter operation to perform (+,-,x,/):");

           String operation= userinput.next();

           if (operation.equals("+"))

           System.out.println(math.Add(num1, num2));

           else if (operation.equals("-"))

           System.out.println(math.Subtract(num1, num2));

           else if (operation.equals("x"))

           System.out.println(math.Multiply(num1, num2));

           else if (operation.equals("/"))

           System.out.println(math.Divide(num1, num2));

           else

           System.out.println("The operation is not valid.");

Simple Calculator

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.event.*;

          class Calc extends JFrame

private static final Font Bigger_font = new Font("monspaced", Font.PLAIN, 20);

private JTextField _displayField;

private boolean   _startNumber = true;

private String    _previousOp  = "=";

private CalcLogic _logic = new CalcLogic();

public static void main(String[] args)

try

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

catch (Exception unused)

        Calc window = new Calc();

        window.setDefaultCloseOperation(JFrame.Exit_On_Close);

        window.setVisible(true);

       public Calc()

        _displayField = new JTextField("0", 12);

        _displayField.setHorizontalAlignment(JTextField.Right);

        _displayField.setFont(Bigger_Font);

        JButton clearButton = new JButton("Clear");

        clearButton.setFont(Bigger_Font);

        clearButton.addActionListener(new ClearListener());

                  ActionListener numListener = new NumListener();

        String buttonOrder = "789456123 0 ";

        JPanel buttonPanel = new JPanel();

        buttonPanel.setLayout(new GridLayout(5, 3, 2, 2));

        for (int i = 0; i < buttonOrder.length(); i++)

            String keyTop = buttonOrder.substring(i, i+1);

            JButton b = new JButton(keyTop);

            if (keyTop.equals(" "))

                           b.setEnabled(false);

            else

                b.addActionListener(numListener);

                b.setFont(Bigger_Font);

            buttonPanel.add(b);

        ActionListener opListener = new OpListener();

        JPanel opPanel = new JPanel();

        opPanel.setLayout(new GridLayout(5, 1, 2, 2));

        String[] opOrder = {"+", "-", "*", "/", "="};

        for (int i = 0; i < opOrder.length; i++)

            JButton b = new JButton(opOrder[i]);

            b.addActionListener(opListener);

            b.setFont(Bigger_Font);

            opPanel.add(b);

        JPanel clearPanel = new JPanel();

        clearPanel.setLayout(new FlowLayout());

        clearPanel.add(clearButton);

        JPanel content = new JPanel();

        content.setLayout(new BorderLayout(5, 5));

        content.add(_displayField, BorderLayout.North );

        content.add(buttonPanel   , BorderLayout.Center);

        content.add(opPanel       , BorderLayout.East  );

        content.add(clearPanel    , BorderLayout.South );

        content.setBorder(BorderFactory.createEmptyBorder(10,10,10,10));

        this.setContentPane(content);

        this.pack();

        this.setTitle("Simple Calc");

        this.setResizable(false);

        this.setLocationRelativeTo(null);

    private void actionClear()

        _startNumber = true;

        _displayField.setText("0");

        _previousOp  = "=";

        _logic.setTotal("0");

    class OpListener implements ActionListener

        public void actionPerformed(ActionEvent e)

             if (_startNumber)

               actionClear();

                _displayField.setText("ERROR - No operator");

              else

              startNumber = true;

try

                    String displayText = _displayField.getText();

                    if (_previousOp.equals("="))

                        _logic.setTotal(displayText);

                    else if (_previousOp.equals("+"))

                        _logic.add(displayText);

                    else if (_previousOp.equals("-"))

                        _logic.subtract(displayText);

                    else if (_previousOp.equals("*"))

                        _logic.multiply(displayText);

                    else if (_previousOp.equals("/"))

                        _logic.divide(displayText);

                   displayField.setText("" + _logic.getTotalString());

                   catch (NumberFormatException ex)

                    actionClear();

                    displayField.setText("Error");

                  previousOp = e.getActionCommand();

    class NumListener implements ActionListener

     public void actionPerformed(ActionEvent e)

            String digit = e.getActionCommand();

            if (_startNumber)

                displayField.setText(digit);

                startNumber = false;

            else

                   displayField.setText(_displayField.getText() + digit);

        class ClearListener implements ActionListener

        public void actionPerformed(ActionEvent e)

            actionClear();

COMPUTER INNOVATIONS