Java Calc (1of2)

//package calculator;   //can't get this to work.


/**
 * This class is the part of the calculator program.
 * It does all of the processing of the data after each button is pressed.
 * The other part of the program is in the class CalcGUI.
 * @author me */
public class CalcMain {

    /**
    * name of calculator GUI object
    */
    private static CalcGUI myCalc;
    /**
    * current operator
    */
    private static char op;
    /**
    * registers or variables for storing the numbers that have been entered
    */
    private static double x,y;

    /** flag to indicate data entry */
    private static boolean dataEntry = false;
    //flag for decimal entry
    /** flag to track how many decimal places we're working with.<br>
    * 1 = none<br>
    * 0 = decimal key has just been pressed<br>
    * -1, -2, -3 ... where the next number is placed in the display
    */
    private static int decimal = 1;

    /**
    * main function creates CalcGUI. That's it.
    * @param args   command-line arguments (not used)
    */
    public static void main(String args[]) {
        myCalc = new CalcGUI();
    }

    /**
    * Processes each button as it is pressed.<br>
    * <b>Called from:</b> CalcGUI<br>
    * <b>Calls:</b> setDisplay() in CalcGUI to set the display of the calculator<br>
    * <b>Assumptions:</b> each each button has unique first character which is used to identify it.
    * @param s  the string that comprises the button text
    */
    static void sendButton(String s) {

        // myCalc.setDisplay("5.22");

        char c = (char)s.charAt(0);
        // System.out.println(c);
        switch (c) {
            case 'C':   //clear
                myCalc.setDisplay("0.0");
                x=0.0;
                dataEntry=false;
                break;
            case '.':
                decimal=0;
                break;
            case '1': case '2': case '3': case '4': case '5':
            case '6': case '7': case '8': case '9': case '0':
                if (dataEntry) {
                    if (decimal < 1) {
                        decimal--;
                        if (x > 0)
                            x = x + Character.getNumericValue(c) * Math.pow(10,decimal);
                        else
                            x = x - Character.getNumericValue(c) * Math.pow(10,decimal);
                    } else
                        if (x > 0)
                            x = x*10.0 + Character.getNumericValue(c);
                        else
                            x = x*10.0 - Character.getNumericValue(c);
                }
                else {
                    x = Character.getNumericValue(c);
                }
                dataEntry=true;
                myCalc.setDisplay(x);
                break;
            case '\u00B1':  // +/-
                x = -1 * x;
                // System.out.println(x + "CHS");
                myCalc.setDisplay(x);
                break;
            case '\u221A':
                x = Math.sqrt(x);   //results in NaN if sqrt of negative number
                myCalc.setDisplay(x);
                dataEntry=false;
                break;
            case '+': case '-': case 'x':
                op = c;
                y=x;
                dataEntry = false;
                break;
            case '\u00F7':
                op = '/';
                y=x;
                dataEntry = false;
                break;
            case '=':
                //perform calculation
                switch (op) {
                case '+':
                    x = y + x;
                    break;
                case '-':
                    x = y - x;
                    break;
                case 'x':
                    x = y * x;
                    break;
                case '/':
                    x = y / x;  //divide by zero results in Infinity. Nice.
                    break;
                }
                myCalc.setDisplay(x);
                dataEntry=false;
                break;
            default: //for testing
                //myCalc.setDisplay(s);
        }
        if (!dataEntry) decimal = 1;
        // System.out.println(x);
    }
}