/src/mpv5/ui/misc/Calc.java

/*
 *  This file is part of YaBS.
 *
 *      YaBS is free software: you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation, either version 3 of the License, or
 *      (at your option) any later version.
 *
 *      YaBS is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU General Public License for more details.
 *
 *      You should have received a copy of the GNU General Public License
 *      along with YaBS.  If not, see <http://www.gnu.org/licenses/>.
 */
package mpv5.ui.misc;

/******************************************************************************
 *
 * Program Name:		Java Calculator Applet
 * Author:				Jason Elias
 * Last Modified:		April 12, 2001
 * Purpose:				Provide all of the basic functions of a calculator in
 *						a GUI environment -- an applet. Also illustrates how
 *						to multithread an applet with two different
 *						implementations to illustrate it: one with a Thread
 *						internally defined in the applet, and a Clock thread
 *						defined outside of the applet.
 *
 * Notes:				Feel free to use and improve this code, and I would love
 *						to see any improvements that are made.
 *
 *						Email:		jasonelias@hotmail.com
 *						Website:	www.geocities.com/entity05
 *
 *****************************************************************************/

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Event;
import java.awt.Font;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.border.EtchedBorder;


public class Calc extends JLabel implements ActionListener,KeyListener {

    private static final long serialVersionUID = 1L;
    int Counter;			//counts the number of digits entered
    double Result;			//the answer displayed, as well as the second
    //operator taken for an operation
    double Operand;			//the first number entered for an operation
    double Mem;				//the variable which holds whatever value the user
    //wants kept in "memory"
    boolean DecimalFlag;	//the 'flag' that will signify whether or not the
    //decimal button has been pressed
    boolean SignFlag;		//the 'flag' that will signify whether or not the
    //plus/minus button has been pressed
    boolean OperatorKey;	//the 'flag' that will signify whether or not any
    //operator button has been pressed
    boolean FunctionKey;	//the 'flag' that will signify whether or not any f
    //function button has been pressed
    int Operator;			//an integer value to indicate which operator
    //button was pressed
    char currchar;			//a character to hold the value of the key most
    //recently pressed
    String GrStatus;		//String to hold the status of various graphic
    //operations of the program
    String Status;			//String to hold the status of various parts

    //This label will display all error messages
     JLabel DisplError = new  JLabel(" ",  JLabel.CENTER);

    /* This label is just to the left of the Display Label lcdDisplay, and will
     * indicate whether or not a value is being held in the calculator's "memory"
     */
     JLabel LabelMem = new JLabel(" ",  JLabel.RIGHT);

    /* This is the Display Label, which is declared as a label so the user will not
     * be able to enter any text into it to possibly crash the calculator
     */
     JLabel lcdDisplay = new  JLabel("0",  JLabel.RIGHT);

    // This is the declaration of all numeric buttons to be used in the applet
     JButton button1 = new  JButton("1");
     JButton button2 = new  JButton("2");
     JButton button3 = new  JButton("3");
     JButton button4 = new  JButton("4");
     JButton button5 = new  JButton("5");
     JButton button6 = new  JButton("6");
     JButton button7 = new  JButton("7");
     JButton button8 = new  JButton("8");
     JButton button9 = new  JButton("9");
     JButton button0 = new  JButton("0");

    /* This is the declaration of all operation buttons that are used in applet.
     * MPlus, MClear and MR are all memory functions.
     */
    JButton buttonMinus = new JButton("-");
    JButton buttonMultiply = new JButton("x");
     JButton buttonPlus = new  JButton("+");
     JButton buttonEquals = new  JButton("=");
     JButton buttonDivide = new  JButton("/");
     JButton buttonClear = new  JButton("C");
     JButton buttonDecimal = new  JButton(".");
     JButton buttonNegative = new  JButton("+/-");
     JButton buttonMPlus = new  JButton("M+");
     JButton buttonMClear = new  JButton("MC");
     JButton buttonMR = new  JButton("MR");
     JButton buttonPercent = new  JButton("%");
     JButton buttonOneOverX = new  JButton("1/X");
     JButton buttonSqr = new  JButton("xÂ?");
     JButton buttonSqrRoot = new  JButton("sqrt");

    public static void main(String[] args) {

        JFrame j = new JFrame();
        j.setLayout(new BorderLayout());

        j.add(new Calc(), BorderLayout.CENTER);
        j.setSize(340, 300);
        j.pack();
        j.setVisible(true);
    }

    /* *This the only method that is called explicitly -- every other method is
     * called depending on the user's actions.
     */
    public Calc() {
        //Allows for configuring a layout with the restraints of a grid or
        //something similar
        setLayout(null);

        //This will resize the applet to the width and height provided
        setSize(340, 300);
//
//        //This sets the default font to Helvetica, plain, size 12
//        setFont(new Font("Helvetica", Font.PLAIN, 12));

        /* Display Panel, which appears at the top of the screen. The label is
         * placed and sized with the setBounds(x,y,width,height) method, and the
         * font, foreground color and background color are all set. Then the
         * label is added to the layout of the applet.
         */
        lcdDisplay.setBounds(2, 15, 308, 30);
        lcdDisplay.setFont(new Font("Helvetica", Font.PLAIN, 20));
        lcdDisplay.setForeground(Color.black);
        lcdDisplay.setBackground(Color.WHITE);
        lcdDisplay.setBorder(new EtchedBorder());
        add(lcdDisplay);

        /* Memory Panel, which appears just to the right of the Display Panel.
         * The label is placed and sized with the setBounds(x,y,width,height)
         * method, and the font, foreground color and background color are all
         * set. Then the label is added to the layout of the applet.
         */
        LabelMem.setBounds(310, 15, 20, 30);
        LabelMem.setFont(new Font("Helvetica", Font.PLAIN, 16));
        LabelMem.setForeground(new Color(65280));
        LabelMem.setBackground(Color.LIGHT_GRAY);
        LabelMem.setBorder(new EtchedBorder());
        add(LabelMem);

        /* The following declarations initialize all of the Numberic Buttons
         * that will displayed on the applet.
         *
         * First, an ActionListener (which will capture events) is added to the
         * button, sending the applet as the argument
         *
         * Second, the button is placed and sized with the setBounds(x,y,width,
         * height) method.
         *
         * Then the default font is set for the button, and the button is added
         * to the layout of the applet.
         */
        button1.addActionListener(this);
        button1.setBounds(2, 65, 60, 34);
        button1.addKeyListener(this);
        add(button1);

        button2.addActionListener(this);
        button2.setBounds(66, 65, 60, 34);
        button2.addKeyListener(this);
        add(button2);

        button3.addActionListener(this);
        button3.setBounds(130, 65, 60, 34);
        button3.addKeyListener(this);
        add(button3);

        button4.addActionListener(this);
        button4.setBounds(2, 104, 60, 34);
        button4.addKeyListener(this);
        add(button4);

        button5.addActionListener(this);
        button5.setBounds(66, 104, 60, 34);
        button5.addKeyListener(this);
        add(button5);

        button6.addActionListener(this);
        button6.setBounds(130, 104, 60, 34);
        button6.addKeyListener(this);
        add(button6);

        button7.addActionListener(this);
        button7.setBounds(2, 142, 60, 34);
        button7.addKeyListener(this);
        add(button7);

        button8.addActionListener(this);
        button8.setBounds(66, 142, 60, 34);
        button8.addKeyListener(this);
        add(button8);

        button9.addActionListener(this);
        button9.setBounds(130, 142, 60, 34);
        button9.addKeyListener(this);
        add(button9);

        button0.addActionListener(this);
        button0.setBounds(2, 180, 60, 34);
        button0.addKeyListener(this);
        add(button0);

        /* The following declaration and initialization statements set up all of
         * the operation buttons on the applet.
         *
         * First, an ActionListener is added to each button with the "this"
         * keyword indicating that "this object" (the applet) is being referred to.
         *
         * Then the button is "reshaped" to a certain coordinate (x and y) as
         * well as new dimensions (width, height).
         *
         * Then the font is set for that button, and the arguments include:
         *		- String value representing the name of the font
         *		- a member of Font called BOLD which bolds the text
         *		- the size of the font as an integer
         *
         * Lastly, the button is added to the applet
         */
        buttonDecimal.addActionListener(this);
        buttonDecimal.setBounds(66, 180, 60, 34);
        buttonDecimal.addKeyListener(this);
        add(buttonDecimal);

        buttonNegative.addActionListener(this);
        buttonNegative.setBounds(130, 180, 60, 34);
        buttonNegative.addKeyListener(this);
        add(buttonNegative);

        buttonMinus.addActionListener(this);
        buttonMinus.setBounds(194, 104, 60, 34);
        buttonMinus.addKeyListener(this);
        add(buttonMinus);

        buttonMultiply.addActionListener(this);
        buttonMultiply.setBounds(194, 142, 60, 34);
        buttonMultiply.addKeyListener(this);
        add(buttonMultiply);

        buttonPlus.addActionListener(this);
        buttonPlus.setBounds(194, 65, 60, 34);
        buttonPlus.addKeyListener(this);
        add(buttonPlus);

        buttonPercent.addActionListener(this);
        buttonPercent.setBounds(2, 230, 60, 34);
        buttonPercent.addKeyListener(this);
//        add(buttonPercent);

        buttonOneOverX.addActionListener(this);
        buttonOneOverX.setBounds(66, 230, 60, 34);
        buttonOneOverX.addKeyListener(this);
        add(buttonOneOverX);

        buttonSqr.addActionListener(this);
        buttonSqr.setBounds(130, 230, 60, 34);
        buttonSqr.addKeyListener(this);
        add(buttonSqr);

        buttonSqrRoot.addActionListener(this);
        buttonSqrRoot.setBounds(194, 230, 60, 34);
        buttonSqrRoot.addKeyListener(this);
        add(buttonSqrRoot);

        buttonEquals.addActionListener(this);
        buttonEquals.setBounds(269, 230, 60, 34);
        buttonEquals.addKeyListener(this);
        add(buttonEquals);

        buttonDivide.addActionListener(this);
        buttonDivide.setBounds(194, 180, 60, 34);
        buttonDivide.addKeyListener(this);
        add(buttonDivide);

        buttonClear.addActionListener(this);
        buttonClear.setBounds(269, 65, 60, 34);
        buttonClear.addKeyListener(this);
        buttonClear.setForeground(new Color(16711680));
        buttonClear.setBackground(new Color(12632256));
        add(buttonClear);

        buttonMPlus.addActionListener(this);
        buttonMPlus.setBounds(269, 104, 60, 34);
        buttonMPlus.addKeyListener(this);
        buttonMPlus.setForeground(Color.blue);
        add(buttonMPlus);

        buttonMClear.addActionListener(this);
        buttonMClear.setBounds(269, 142, 60, 34);
        buttonMClear.addKeyListener(this);
        buttonMClear.setForeground(Color.blue);
        add(buttonMClear);

        buttonMR.addActionListener(this);
        buttonMR.setBounds(269, 180, 60, 34);
        buttonMR.addKeyListener(this);
        buttonMR.setForeground(Color.blue);
        add(buttonMR);

        /* This is the initialization of the DisplayError label. It is placed and
         * sized with the setBounds(x,y,width,height) method, and then the font,
         * foreground color and background color are all set. Finally, the label
         * is added to the layout of the applet.
         */
        DisplError.setBounds(2, 278, 329, 15);
        DisplError.setFont(new Font("Dialog", Font.BOLD, 12));
        DisplError.setForeground(new Color(16711680));
        DisplError.setBackground(new Color(0));
        add(DisplError);


        Clicked_Clear();			//calls the Clicked_Clear method (C button)

    }	//end of calc init method

    /* The following integer values are being set as "final" because
     * they are going to be used for determining what button has been
     * pushed
     */
    public final static int OpMinus = 11,  OpMultiply = 12,  OpPlus = 13,  OpDivide = 15,  OpMPlus = 19,  OpMClear = 20,  OpMR = 21;

    /* This method is called whenever anything needs to be displayed
     * in the error message field at the bottom of the calculator,
     * accepting a String as an argument
     */
    void DisplayError(String err_msg) {
        /* calls the setText method of the Label DisplError, sending
         * whatever string it received initially
         */
        DisplError.setText(err_msg);
    }

    /* This method is called whenever a numeric button (0-9) is pushed. */
    public void NumericButton(int i) {
        DisplayError(" ");			//Clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        /* Checks if an operator key has just been pressed, and if it has,
         * then the limit of 20 digits will be reset for the user so that
         * they can enter in up to 20 new numbers
         */
        if (OperatorKey == true) {
            Counter = 0;
        }

        Counter = Counter + 1;		//increments the counter

        /* This is a condition to see if the number currently displayed is zero OR
         * an operator key other than +, -, *, or / has been pressed.
         */
        if ((Display.equals("0")) || (Status.equals("FIRST"))) {
            Display = "";			//Do not display any new info
        }

        if (Counter < 21) //if more than 20 numbers are entered
        {
            //The number just entered is appended to the string currently displayed
            Display = Display + String.valueOf(i);
        } else {
            //call the DisplayError method and send it an error message string
            DisplayError("Digit Limit of 20 Digits Reached");
        }

        lcdDisplay.setText(Display);	//sets the text of the lcdDisplay
        //Label

        Status = "VALID";				//sets the Status string to valid
        OperatorKey = false;			//no operator key was pressed
        FunctionKey = false;			//no function key was pressed
    }

    /* This method is called whenever an operator button is pressed, and is
     * sent an integer value representing the button pressed.
     */
    public void OperatorButton(int i) {
        DisplayError(" ");			//Clears the error message field

        /* Creates a new Double object with the specific purpose of retaining
         * the string currently on the lcdDisplay label, and then immediately
         * converts that string into a double-precision real number and then
         * gives that number to the variable Result.
         */
        Result = (new Double(lcdDisplay.getText())).doubleValue();

        //If no operator key has been pressed OR a function has been pressed
        if ((OperatorKey == false) || (FunctionKey = true)) {
            switch (Operator) //depending on the operation performed
            {
                /* if the user pressed the addition button, add the two numbers
                 * and put them in double Result
                 */
                case OpPlus:
                    Result = Operand + Result;
                    break;

                /* if the user pressed the subtraction button, subtract the two
                 * numbers and put them in double Result
                 */
                case OpMinus:
                    Result = Operand - Result;
                    break;

                /* if the user pressed the multiplication button, multiply
                 * the two numbers and put them in double Result
                 */
                case OpMultiply:
                    Result = Result * Operand;
                    break;

                /* if the user pressed the division button, check to see if
                 * the second number entered is zero to avoid a divide-by-zero
                 * exception
                 */
                case OpDivide:
                    if (Result == 0) {
                        //set the Status string to indicate an
                        //an error
                        Status = "ERROR";

                        //display the word "ERROR" on the
                        //lcdDisplay label
                        lcdDisplay.setText("ERROR");

                        /* call the DisplayError method and
                         * send it a string indicating an error
                         * has occured and of what type
                         */
                        DisplayError("ERROR: Division by Zero");
                    } else {
                        //divide the two numbers and put the
                        //answer in double Result
                        Result = Operand / Result;
                    }
            }

            //if after breaking from the switch the Status string is not set
            //to "ERROR"
            if (!Status.equals("ERROR")) {
                Status = "FIRST";	/* set the Status string to "FIRST" to
                 * indicate that a simple operation was
                 * not performed
                 */

                Operand = Result;	//Operand holds the value of Result

                Operator = i;		/* the integer value representing the
                 * operation being performed is stored
                 * in the integer Operator
                 */

                //The lcdDisplay label has the value of double Result
                //displayed
                lcdDisplay.setText(String.valueOf(Result));

                //The boolean decimal flag is set false, indicating that the
                //decimal button has not been pressed
                DecimalFlag = false;

                //The boolean sign flag is set false, indicating that the sign
                //button has not been pressed
                SignFlag = false;

                //The boolean OperatorKey is set true, indicating that a simple
                //operation has been performed
                OperatorKey = true;

                //The boolean FunctionKey is set false, indicating that a
                //function key has not been pressed
                FunctionKey = false;

                DisplayError(" ");		//Clears the error message field
            }

        }

    }			//end of OperatorButton method

    /* This is a method that is called whenever the decimal button is
     * pressed.
     */
    public void DecimalButton() {
        DisplayError(" ");		//Clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        //if a simple operation was performed successfully
        if (Status .equals("FIRST")) {
            Display = "0";		//set Display string to character 0
        }

        //If the decimal button has not already been pressed
        if (!DecimalFlag) {
            //appends a decimal to the string Display
            Display = Display + ".";
        } else {
            /* calls the DisplayError method, sending a string
             * indicating that the number already has a decimal
             */
            DisplayError("Number already has a Decimal Point");
        }

        /* calls the setText method of the Label lcdDisplay and
         * sends it the string Display
         */
        lcdDisplay.setText(Display);
        DecimalFlag = true;		//the decimal key has been pressed
        Status = "VALID";		/* Status string indicates a valid
         * operation has been performed
         */
        OperatorKey = false;    //no operator key has been pressed

    }	//end of the DecimalButton method

    /* This method is called whenever the percent button is pressed
     */
    void PercentButton() {
        DisplayError(" ");		//clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        /* if the Status string is not set to "FIRST" OR the Display string
         * does not currently hold the value "0"
         */
        if ((!Status.equals("FIRST")) || (!Display.equals("0"))) {
            /* Creates a new Double object with the specific purpose of retaining
             * the string currently on the lcdDisplay label, and then immediately
             * converts that string into a double-precision real number and then
             * gives that number to the variable Result.
             */
            Result = (new Double(lcdDisplay.getText())).doubleValue();

            //divide the double Result by 100, getting the percentage
            Result = Result / 100;

            /* call the setText method of Label lcdDisplay and send it the string
             * that represents the value in Result
             */
            lcdDisplay.setText(String.valueOf(Result));
            Status = "FIRST";		//
            OperatorKey = true;		//an operator key has been pressed
            FunctionKey = true;		//a function key has been pressed
        }
    }	//end of the PercentButton method

    /* This method is called first when the calculator is initialized
     * with the init() method, and is called every time the "C" button
     * is pressed
     */
    void Clicked_Clear() {
        Counter = 0;				//sets the counter to zero
        Status = "FIRST";			//sets Status to FIRST
        Operand = 0;				//sets Operand to zero
        Result = 0;					//sets Result to zero
        Operator = 0;				//sets Operator integer to zero

        DecimalFlag = false;		//decimal button has not been
        //pressed

        SignFlag = false;			//sign button has not been pressed

        OperatorKey = false;		//no operator button has been
        //pressed

        FunctionKey = false;		//no function button has been
        //pressed

        /* calls the setText method of Label lcdDisplay and sends
         * it the character "0"
         */
        lcdDisplay.setText("0");
        DisplayError(" ");			//clears the error message field
    }

    /* This method is called whenever the sign button is pressed */
    void PlusMinusButton() {
        DisplayError(" ");			//clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        /* if Status is not set to FIRST and the Display string does not
         * hold the value "0"
         */
        if ((!Status.equals("FIRST")) || (!Display.equals("0"))) {
            /* Creates a new Double object with the specific purpose of retaining
             * the string currently on the lcdDisplay label, and then immediately
             * converts that string into a double-precision real number and then
             * gives that number to the variable Result.
             */
            Result = (new Double(lcdDisplay.getText())).doubleValue();

            //sets the double Result to it's negative value
            Result = -Result;

            /* call the setText method of Label lcdDisplay and send it the string
             * that represents the value in Result
             */
            lcdDisplay.setText(String.valueOf(Result));
            Status = "VALID";		//sets Status string to VALID
            SignFlag = true;		//the sign button has been pressed
            DecimalFlag = true;		//a decimal has appeared
        }
    }	//end of the PlusMinusButton method

    /* This method is called whenever the square button is pressed */
    void SqrButton() {
        DisplayError(" ");			//clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        /* if Status is not set to FIRST and the Display string does not
         * hold the value "0"
         */
        if ((!Status.equals("FIRST")) || (!Display.equals("0")) ){
            /* Creates a new Double object with the specific purpose of retaining
             * the string currently on the lcdDisplay label, and then immediately
             * converts that string into a double-precision real number and then
             * gives that number to the variable Result.
             */
            Result = (new Double(lcdDisplay.getText())).doubleValue();

            /* multiply the double Result by itself, effectively squaring
             * the number */
            Result = Result * Result;

            /* call the setText method of Label lcdDisplay and send it the string
             * that represents the value in Result
             */
            lcdDisplay.setText(String.valueOf(Result));

            Status = "FIRST";		//indicates this is the first time
            //this button has been pressed

            OperatorKey = true;		//an operator button has been pressed
            FunctionKey = true;		//a function button has been pressed
        }
    }	//end of the SqrButton method

    /* This method is called whenever the square button is pressed */
    void SqrRootButton() {
        DisplayError(" ");			//clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        /* if Status is not set to FIRST and the Display string does not
         * hold the value "0"
         */
        if ((!Status.equals("FIRST")) || (!Display.equals( "0"))) {
            /* Creates a new Double object with the specific purpose of retaining
             * the string currently on the lcdDisplay label, and then immediately
             * converts that string into a double-precision real number and then
             * gives that number to the variable Result.
             */
            Result = (new Double(lcdDisplay.getText())).doubleValue();

            /* Makes a call to the Math class method "sqrt", which produced the
             * square root and stores the value in Result
             */
            Result = Math.sqrt(Result);

            /* call the setText method of Label lcdDisplay and send it the string
             * that represents the value in Result
             */
            lcdDisplay.setText(String.valueOf(Result));

            Status = "FIRST";		//indicates this is the first time
            //this button has been pressed

            OperatorKey = true;		//an operator button has been pressed
            FunctionKey = true;		//a function button has been pressed
        }
    }	//end of the SqrRootButton method

    /* This method is called whenever the OneOverXButton is pressed */
    void OneOverXButton() {
        DisplayError(" ");			//clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        /* if Status is not set to FIRST and the Display string does not
         * hold the value "0"
         */
        if ((!Status.equals( "FIRST")) || (!Display .equals("0"))) {
            /* Creates a new Double object with the specific purpose of retaining
             * the string currently on the lcdDisplay label, and then immediately
             * converts that string into a double-precision real number and then
             * gives that number to the variable Result.
             */
            Result = (new Double(lcdDisplay.getText())).doubleValue();

            //divides one by the double Result
            Result = 1 / Result;

            /* call the setText method of Label lcdDisplay and send it the string
             * that represents the value in Result
             */
            lcdDisplay.setText(String.valueOf(Result));

            Status = "FIRST";		//indicates that this is the first time
            //this button has been pressed

            OperatorKey = true;		//an operator key has been pressed
            FunctionKey = true;		//a function key has been pressed
        }
    }	//end of the OneOverXButton method

    /* This method is called whenever one of the three memory buttons is pressed,
     * accepting an integer representing the button pressed as an argument
     */
    void MemoryButton(int i) {
        DisplayError(" ");			//clears the error message field

        /* Declares a String called Display that will initialize to whatever
         * is currently displayed in the lcdDisplay of the calculator
         */
        String Display = lcdDisplay.getText();

        //depending on the value sent representing the buttons
        switch (i) {
            /* if the M+ button is pressed, check if the Display string has the value
             * "0." OR just "0", but along with the second condition check if double
             * Mem holds the value zero
             */
            case OpMPlus:
                if (((Display.equals("0.")) || (Display.equals("0"))) && (Mem == 0)) {
                    //clears the LabelMem label
                    LabelMem.setText(" ");
                } else {
                    /* Creates a new double variable called temp, which accepts the
                     * double value of a new Double object retaining the string
                     * currently on the lcdDisplay label, and then immediately
                     * converts that string into a double-precision real number
                     */
                    double temp = (new Double(lcdDisplay.getText())).doubleValue();

                    //set the Mem variable with that the sum of what's currently in
                    //Mem and the temp variable
                    Mem = Mem + temp;

                    /* calls the setText method of the Label LabelMem, sending
                     * it the character "M"
                     */
                    LabelMem.setText("M");
                }
                break;

            /* if the MR button is pressed, call the setText method of Label lcdDisplay,
             * sending it the string that represents what the value of Mem is
             */
            case OpMR:
                lcdDisplay.setText(String.valueOf(Mem));
                break;

            /* if the MC button is pressed, set the Mem variable to zero */
            case OpMClear:
                Mem = 0;

                //clears the LableMem field
                LabelMem.setText(" ");
                break;
        }
        Status = "FIRST";			//indicates that this is first time
        //button has been pressed

        OperatorKey = true;			//an operator button has been pressed

        //if the Mem variable has the value zero
        if (Mem == 0) {
            LabelMem.setText(" ");	//clear the LabelMem field
        }
    }	//end of the MemoryButton method

    /* This was left commented out so that a shell would be ready if needed
    public void paint(Graphics g)
    {

    }*/
    /***************************************************************************
     *
     * This is the overridden update method for this applet -- update is used to
     * eliminate the flicker that happens with repainting an image from scratch.
     *
     **************************************************************************/
//    public void update(Graphics g) {
//        /* The format of the coordinates below is:
//         *		x position on the applet
//         *		y position on the applet
//         *		width of the component
//         *		height of the component
//         */
//
//        //Sets the color to white and draw a rectangle around the applet
//        g.setColor(Color.white);
//        g.drawRect(0, 0, 420, 368);
//
//        //sets the color to black and draws lines down the east and south sides
//        //of the applet to make it appear three-dimensional
//        g.setColor(Color.black);
//        g.drawLine(419, 0, 419, 367);
//        g.drawLine(0, 367, 419, 367);
//
//        //sets the color to gray and draws lines right next to the black lines
//        //to enhance the three-dimensional effect
//        g.setColor(Color.gray);
//        g.drawLine(418, 1, 418, 366);
//        g.drawLine(1, 366, 418, 366);
//
//        //sets the color to gray and draws a rectangle around the lcdDisplay
//        //label to give it some depth
//        g.setColor(Color.gray);
//        g.drawRect(41, 14, 329, 31);
//
//        //sets the color to yellow and draws a rectangle around the DisplError
//        //label to give it some importance and help attract the eye to errors
//        //displayed there
//        g.setColor(Color.yellow);
//        g.drawRect(41, 277, 330, 16);
//
//
//    }

    /************************************************************************
    /*
    /* This method is called whenever an action is performed on the applet,
    /* specifically whenever one of the buttons on the applet is pressed
    /*
     * /***********************************************************************
     * @param event 
     */
    public void actionPerformed(ActionEvent event) {
        /* Declares an object named "src" to represent the event.getSource()
         * method. This shortens the code that follows.
         */
        Object src = event.getSource();

        /* Checks to see if the source of the event which src is representing
         * is a Button and can behave like a Button
         */
        if (src instanceof JButton) {
            /* Checks to see if Status string holds the value ERROR OR if the
             * source of the event is the buttonClear ("C") button
             */
            if ((!Status.equals( "ERROR")) || (src.equals(buttonClear))) {
                /* The following conditions check for numeric buttons that have
                 * been pressed, and then called the method NumericButton and
                 * send it an integer value depending on the value of the button
                 * pressed
                 */
                if (src == button1) {
                    NumericButton(1);
                }
                if (src == button2) {
                    NumericButton(2);
                }
                if (src == button3) {
                    NumericButton(3);
                }
                if (src == button4) {
                    NumericButton(4);
                }
                if (src == button5) {
                    NumericButton(5);
                }
                if (src == button6) {
                    NumericButton(6);
                }
                if (src == button7) {
                    NumericButton(7);
                }
                if (src == button8) {
                    NumericButton(8);
                }
                if (src == button9) {
                    NumericButton(9);
                }
                if (src == button0) {
                    NumericButton(0);
                }

                /* The following conditions check for operator buttons that have
                 * been pressed, and then call the OperatorButton method, sending
                 * the corresponding integer value
                 */
                if (src == buttonMinus) {
                    OperatorButton(11);
                }
                if (src == buttonMultiply) {
                    OperatorButton(12);
                }
                if (src == buttonPlus) {
                    OperatorButton(13);
                }
                if (src == buttonEquals) {
                    OperatorButton(14);
                }
                if (src == buttonDivide) {
                    OperatorButton(15);
                }

                /* This condition checks if the decimal button has been pressed,
                 * and then calls the DecimalButton method
                 */
                if (src == buttonDecimal) {
                    DecimalButton();
                }

                /* This condition checks if the percent button has been pressed,
                 * and then calls the PercentButton method
                 */
                if (src == buttonPercent) {
                    PercentButton();
                }

                /* This condition checks if the clear button has been pressed,
                 * and then calls the Clicked_Clear method
                 */
                if (src == buttonClear) {
                    Clicked_Clear();
                }

                /* This condition checks if the Plus Minus Button has been
                 * pressed, and then calls the PlusMinusButton method
                 */
                if (src == buttonNegative) {
                    PlusMinusButton();
                }

                /* This condition checks if the Square Button has been pressed,
                 * and then calls the SqrButton method
                 */
                if (src == buttonSqr) {
                    SqrButton();
                }

                /* This condition checks if the Square Root Button has been
                 * pressed, and then calls the SqrRootButton method
                 */
                if (src == buttonSqrRoot) {
                    SqrRootButton();
                }

                /* This condition checks if the One over X Button has been
                 * pressed, and then calls the OneOverXButton method
                 */
                if (src == buttonOneOverX) {
                    OneOverXButton();
                }

                /* These conditions checks to see if any of the Memory Buttons
                 * have been pressed, and then calls the MemoryButton method and
                 * sends them the corresponding integer values
                 */
                if (src == buttonMPlus) {
                    MemoryButton(19);
                }

                if (src == buttonMClear) {
                    MemoryButton(20);
                }

                if (src == buttonMR) {
                    MemoryButton(21);
                }
            }
        }
    }			//end of actionPerformed method

    /****************************************************************************
     *
     * The following method handles all of the key events that occurs when a user
     * enters values from the keyboard. It accepts an Event object and an integer
     * representing the key pressed as arguments.
     *
     * It should be noted that in order to accept keys entered to the lcdDisplay,
     * the applet must be in focus.
     *
     **************************************************************************
     * @param evt
     * @param key
     */
  
    public void keyD(KeyEvent evt, char key) {
        //assigns key value to currchar through typecasting key to a character
        currchar = key;

        /* The following conditions check to see if a number key has been pressed
         * and calls the NumericButton method, sending it the appropriate integer
         * as an argument
         */
        if (currchar == '0') {
            NumericButton(0);
        }
        if (currchar == '1') {
            NumericButton(1);
        }
        if (currchar == '2') {
            NumericButton(2);
        }
        if (currchar == '3') {
            NumericButton(3);
        }
        if (currchar == '4') {
            NumericButton(4);
        }
        if (currchar == '5') {
            NumericButton(5);
        }
        if (currchar == '6') {
            NumericButton(6);
        }
        if (currchar == '7') {
            NumericButton(7);
        }
        if (currchar == '8') {
            NumericButton(8);
        }
        if (currchar == '9') {
            NumericButton(9);
        }

        /* The following conditions check to see if any of the operator keys
         * which are on the number pad have been pressed. It then calls the
         * OperatorButton method, sending it the appropriate integer value as
         * an argument.
         *
         * It should be noted that the main functions checked for are those on
         * the number pad, but if they are pressed at other occurences on the
         * keyboard, they are still accepted.
         */
        if (currchar == '/') {
            OperatorButton(15);
        }
        if (currchar == '*') {
            OperatorButton(12);
        }
        if (currchar == '-') {
            OperatorButton(11);
        }
        if (currchar == '+') {
            OperatorButton(13);
        }

        if (currchar == '=') {
            OperatorButton(14);
        }

        //This condition is different from the others because it tests for the
        //Enter key being pressed, and this is pre-built into the Event evt
        //object
        if (currchar == Event.ENTER) {
            OperatorButton(14);
        }

        /* This checks for the decimal key being pressed, either on the number
         * pad or the period key, and calls the DecimalButton method.
         */
        if (currchar == '.') {
            DecimalButton();
        }

    }

    public void keyTyped(KeyEvent evt) {
       keyD(evt, evt.getKeyChar());
    }

    public void keyPressed(KeyEvent e) {
       
    }

    public void keyReleased(KeyEvent e) {
       
    }
}