Sunday, January 11, 2015

Simple Calculator Project in JAVA

Simple Calculator in JAVA

This is a simple java calculator project to calculate basic arithmetic operations using GUI features of Java extending JFrame Class. The source code is organized in two files. They are:
1. Main.java and
2. Calc_Frame.java

Before actually digging deeper into the source code, lets first see the the output of the project tested with an input expression 9/2*3 whose obvious output after calculation is 13.5
Here are the snapshots:
Figure: Input of test expression 9/2*3


Figure: Result of test input expression.

1. Main.java

//Contents of the file "Main.java"
/**
 * Created by Bikal Adhikari on 12/18/2014.
 */
public class Main {
    public static void main(String[] args) {
        Calc_Frame m=new Calc_Frame("BKL-Calculator");
    }
}

2. Calc_Frame.java

//Contents of the file  "Calc_Frame.java"
/**
 * Created by Bikal Adhikari on 12/18/2014.
 */
import java.awt.Container;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;


public class Calc_Frame extends JFrame {
    JPanel p1 = new JPanel();
    JPanel p2 = new JPanel();
    /*Text Field For emulating Calculator Screen*/
    JTextArea CalcScreen = new JTextArea();
    /*Defining Buttons For keys of Calculator*/
    JButton b0 = new JButton("7");
    JButton b1 = new JButton("8");
    JButton b2 = new JButton("9");
    JButton b3 = new JButton("/");
    JButton b4 = new JButton("4");
    JButton b5 = new JButton("5");
    JButton b6 = new JButton("6");
    JButton b7 = new JButton("*");
    JButton b8 = new JButton("1");
    JButton b9 = new JButton("2");
    JButton b10 = new JButton("3");
    JButton b11 = new JButton("-");
    JButton b12 = new JButton("0");
    JButton b13 = new JButton(".");
    JButton b14 = new JButton("=");
    JButton b15 = new JButton("+");


    public Calc_Frame(String str) {
        super(str);
        Container c = getContentPane();
        p1.setLayout(new GridLayout(1, 1, 10, 450));
        p2.setLayout(new GridLayout(4, 4));
        p1.add(CalcScreen);
        CalcScreen.setEditable(false);



        /*Adding Buttons to panel p2*/
        p2.add(b0);
        p2.add(b1);
        p2.add(b2);
        p2.add(b3);
        p2.add(b4);
        p2.add(b5);
        p2.add(b6);
        p2.add(b7);
        p2.add(b8);
        p2.add(b9);
        p2.add(b8);
        p2.add(b9);
        p2.add(b10);
        p2.add(b11);
        p2.add(b12);
        p2.add(b13);
        p2.add(b14);
        p2.add(b15);
        /*Adding panels to container */
        c.add(p1);
        c.add(p2, BorderLayout.SOUTH);
       /*Setting Size of the Frame*/
        setSize(250, 200);
        setVisible(true);
       /*Handler for Button Event Handling*/
        Handler h = new Handler();
       /*Registering Handler into Action Listener*/
        b0.addActionListener(h);
        b1.addActionListener(h);
        b2.addActionListener(h);
        b3.addActionListener(h);
        b4.addActionListener(h);
        b5.addActionListener(h);
        b6.addActionListener(h);
        b7.addActionListener(h);
        b8.addActionListener(h);
        b9.addActionListener(h);
        b10.addActionListener(h);
        b11.addActionListener(h);
        b12.addActionListener(h);
        b13.addActionListener(h);
        b14.addActionListener(h);
        b15.addActionListener(h);
    }
/*Class to handle event generated by the button press*/
 class Handler implements ActionListener {
     int pos=0;
     public void actionPerformed(ActionEvent e) {
            if (e.getSource() == b0) {
                pos = CalcScreen.getCaretPosition(); //get the cursor position
                CalcScreen.insert("7",pos);
            }
         if (e.getSource() == b1) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("8",pos);
         }
         if (e.getSource() == b2) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("9",pos);
         }
         if (e.getSource() == b3) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("/",pos);
         }
         if (e.getSource() == b4) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("4",pos);

         }
         if (e.getSource() == b5) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("5",pos);
         }
         if (e.getSource() == b6) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("6",pos);
         }
         if (e.getSource() == b7) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("*",pos);
         }
         if (e.getSource() == b8) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("1",pos);
         }
         if (e.getSource() == b9) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("2",pos);
         }
         if (e.getSource() == b10) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("3",pos);
         }
         if (e.getSource() == b11) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("-",pos);
         }
         if (e.getSource() == b12) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("0",pos);
         }
         if (e.getSource() == b13) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert(".",pos);
         }

         //Equals to Button
         if (e.getSource() == b14) {
             String str=CalcScreen.getText();
             double a=eval(str);
             CalcScreen.setText(null);
             String abc = Double.toString(a);
             CalcScreen.insert(abc,0);

         }
         if (e.getSource() == b15) {
             pos = CalcScreen.getCaretPosition(); //get the cursor position
             CalcScreen.insert("+",pos);
         }
        }


    }//Class Handler Ends Here

 /**
  * This Function performs job of parsing arithmetic expressions given to the calculator
  * It basically supports parsing expression containing Division, Multiplication, Addition and Subtraction
  * */
    public static double eval(final String str) {
        class Parser {//Nested Class
            int pos = -1, c;

            void eatChar() {
                c = (++pos < str.length()) ? str.charAt(pos) : -1;
            }

            void eatSpace() {
                while (Character.isWhitespace(c)) eatChar();
            }

            double parse() {
                eatChar();
                double v = parseExpression();
                if (c != -1) throw new RuntimeException("Unexpected: " + (char)c);
                return v;
            }

            // Grammar:
            // expression = term | expression `+` term | expression `-` term
            // term = factor | term `*` factor | term `/` factor | term brackets
            // factor = brackets | number | factor `^` factor
            // brackets = `(` expression `)`

            double parseExpression() {
                double v = parseTerm();
                for (;;) {
                    eatSpace();
                    if (c == '+') { // addition
                        eatChar();
                        v += parseTerm();
                    } else if (c == '-') { // subtraction
                        eatChar();
                        v -= parseTerm();
                    } else {
                        return v;
                    }
                }
            }

            double parseTerm() {
                double v = parseFactor();
                for (;;) {
                    eatSpace();
                    if (c == '/') { // division
                        eatChar();
                        v /= parseFactor();
                    } else if (c == '*' || c == '(') { // multiplication
                        if (c == '*') eatChar();
                        v *= parseFactor();
                    } else {
                        return v;
                    }
                }
            }

            double parseFactor() {
                double v;
                boolean negate = false;
                eatSpace();
                if (c == '(') { // brackets
                    eatChar();
                    v = parseExpression();
                    if (c == ')') eatChar();
                } else { // numbers
                    if (c == '+' || c == '-') { // unary plus & minus
                        negate = c == '-';
                        eatChar();
                        eatSpace();
                    }
                    StringBuilder sb = new StringBuilder();
                    while ((c >= '0' && c <= '9') || c == '.') {
                        sb.append((char)c);
                        eatChar();
                    }
                    if (sb.length() == 0) throw new RuntimeException("Unexpected: " + (char)c);
                    v = Double.parseDouble(sb.toString());
                }
                eatSpace();
                if (c == '^') { // exponentiation
                    eatChar();
                    v = Math.pow(v, parseFactor());
                }
                if (negate) v = -v; // exponentiation has higher priority than unary minus: -3^2=-9
                return v;
            }
        }
        return new Parser().parse();
    }
}//Class Calc_Frame ends here


All the necessary project files are included in this zipped archive. To download click here.

"Enjoy Learning"



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