Java Scientific Calculator

class Calculator{
    public static void main(String[] args){
        EventQueue.invokeLater(new Runnable(){
            public void run(){
                CalculatorFrame frame = new CalculatorFrame();
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setVisible(true);
                }
            }
        );
    }
}


class CalculatorFrame extends JFrame{
    public CalculatorFrame(){
    setTitle("Calculator");
    CalculatorPanel panel = new CalculatorPanel();
    add(panel);
    pack();
    }
}


class CalculatorPanel extends JPanel{
    public CalculatorPanel(){
        setLayout(new BorderLayout());
        result = 0;
        lastCommand = "=";
        start = true;
        // add the display
        display = new JButton("");
        display.setEnabled(false);
        add(display, BorderLayout.NORTH);
        ActionListener insert = new InsertAction();
        ActionListener command = new CommandAction();
        // add the buttons in a  x  grid
        panel = new JPanel();
        panel.setLayout(new GridLayout(4,4 ));
        addButton("7", insert);
        addButton("8", insert);
        addButton("9", insert);
        addButton("/", command);

        addButton("4", insert);
        addButton("5", insert);
        addButton("6", insert);
        addButton("*", command);

        addButton("1", insert);
        addButton("2", insert);
        addButton("3", insert);
        addButton("-", command);
        addButton("0", insert);
        addButton(".", insert);
        addButton("=", command);
        addButton("+", command);
        add(panel, BorderLayout.CENTER);
    }

    private void addButton(String label, ActionListener listener){
        JButton button = new JButton(label);
        button.addActionListener(listener);
        panel.add(button);
    }

    private class InsertAction implements ActionListener{
        public void actionPerformed(ActionEvent event){
            String input = event.getActionCommand();
            if (start){
                display.setText("");
                start = false;
            }
            display.setText(display.getText() + input);
        }
    }


    private class CommandAction implements ActionListener{
        public void actionPerformed(ActionEvent event) {
            String command = event.getActionCommand();

            if (start){
                if (command.equals("-")){
                display.setText(command);
                start = false;
                }
                else lastCommand = command;
            }
            else{
                calculate(Double.parseDouble(display.getText()));
                lastCommand = command;
                start = true;
            }
        }
    }


    public void calculate(double x){
        if (lastCommand.equals("+")) result += x;
        else if (lastCommand.equals("-")) result -= x;
        else if (lastCommand.equals("*")) result *= x;
        else if (lastCommand.equals("/")) result /= x;
        else if (lastCommand.equals("=")) result = x;
        display.setText("" + result);
    }

    private JButton display;
    private JPanel panel;
    private double result;
    private String lastCommand;
    private boolean start;
}

W.A.P to Find ODD or EVEN in Java

import java.util.Scanner;
class oddeven
{
    public static void main(String []args)
    {
        int x;
        System.out.println("Enter the Number");
        Scanner obj=new Scanner(System.in);
        x=obj.nextInt();
       
        if(x%2==0)
        {   
            System.out.println("Even Number");
        }
        else
        {
            System.out.println("Odd Number");
        }
    }
}

W.A.P. to Prints multiplication table of a number entered by the user using a for loop.

import java.util.Scanner;
class Mul
{
    public static void main(String []args)  
    {
        int n,c;
        System.out.println("Enter an integer to print it's

multiplication table");
  
    Scanner in=new Scanner(System.in);
    n=in.nextInt();
    System.out.println("Multiplication Table Of "+n+" is :-");

    for(c=1;c<=10;c++)

    System.out.println(n+"*"+c+" = "+(n*c));
    }

}

How to open notepad using Java program

import java.util.*;
import java.io.*;
 
class Notepad {
  public static void main(String[] args) {
    Runtime rs = Runtime.getRuntime();
 
    try {
      rs.exec("notepad");
    }
    catch (IOException e) {
      System.out.println(e);
    }   
  }
}

W.A.P Bubble Sort in JAVA

import java.util.Scanner;
 
class BubbleSort {
  public static void main(String []args) {
    int n, c, d, swap;
    Scanner in = new Scanner(System.in);
 
    System.out.println("Input number of integers to sort");
    n = in.nextInt();
 
    int array[] = new int[n];
 
    System.out.println("Enter " + n + " integers");
 
    for (c = 0; c < n; c++) 
      array[c] = in.nextInt();
 
    for (c = 0; c < ( n - 1 ); c++) {
      for (d = 0; d < n - c - 1; d++) {
        if (array[d] > array[d+1]) /* For descending order use < */
        {
          swap       = array[d];
          array[d]   = array[d+1];
          array[d+1] = swap;
        }
      }
    }
 
    System.out.println("Sorted list of numbers");
 
    for (c = 0; c < n; c++) 
      System.out.println(array[c]);
  }
}