calculator HELP!!

[mandy335]

[CODE=java]public class Calculator {

private long input = 0; // current input
private long result = 0; // last input/result
private String lastOperator = ""; // keeps track of the last operator entered


/* Digit entered as integer value i
* Updates the value of input accordingly to (input * 10) + i
*/
public void inDigit(long i) {
input = (input * 10) + i;
//System.out.prin tln("** inDigit **input " + input + " **result " + result);
}


/* Operator entered + - or *
*/
public void inOperator(Stri ng op) {
inEquals();
// save the current input as result to get ready for next input
input = 0;
// remember which operator was entered
lastOperator = op;
}


/* Equals operation
* sets result to current result + - or * input (depending on
lastOperator)
*/
public void inEquals() {
if (lastOperator.e quals("+")) {
result += input;
} else if (lastOperator.e quals("-")) {
result -= input;
} else if (lastOperator.e quals("*")) {
result *= input;
} else {
result = input;
}
// reset last operator to "nothing"
lastOperator = "";
}


/* Clear operation */
public void inClear() {
input = 0;
result = 0;
lastOperator = "";
}

/* return the current result */
public long getResult() {
return result;
}

/* return the current input value */
public long getCurrentInput () {
return input;
}

public void clearInput(){
input = 0;
}


}









import javax.swing.*;
import java.awt.event. *;
import java.awt.*;
import java.util.Scann er;

public class CalculatorPanel extends JPanel {

// an array of buttons displayed on the calculator
private JButton[] digitButtons;

// output display for the calculator
private JTextField display = new JTextField(10);

private Calculator calc = new Calculator();

/*main method - sets up JFrame*/
public static void main(String [] args){
JFrame frame = new JFrame("Calcula tor");
frame.setConten tPane(new CalculatorPanel ());
frame.setDefaul tCloseOperation (JFrame.EXIT_ON _CLOSE);
frame.pack();
frame.setVisibl e(true);
}

/* Constructor -- builds a GUI for a calculator */
public CalculatorPanel () {

/* create an array of button labels */
String[] buttonLabels = {"1", "2", "3", "4", "5", "6",
"7", "8", "9", "C", "0", "=", "+", "-", "*"};

/* Create an array of buttons. */
digitButtons = new JButton[buttonLabels.le ngth];

/* Create an actionListener */
ButtonListener listener = new ButtonListener( );

/* Create a 5 x 3 grid for placement of buttons. */
JPanel buttonGrid = new JPanel();
buttonGrid.setL ayout(new GridLayout(5, 3));

/* Create a button with each button label, add it to buttonGrid,
* and register the button as a listener. */
for (int nextBut = 0; nextBut < digitButtons.le ngth; nextBut++) {
digitButtons[nextBut] = new JButton(buttonL abels[nextBut]);
buttonGrid.add( digitButtons[nextBut]);
digitButtons[nextBut].addActionListe ner(listener);
}

/* Create a message for the user*/
JLabel instruct = new JLabel("Press a button");

/* add the components to this JPanel*/
setLayout(new BorderLayout()) ;
add(instruct, BorderLayout.NO RTH);
add(buttonGrid, BorderLayout.CE NTER);
add(display, BorderLayout.SO UTH);
}


/* represents a listener for button presses */
private class ButtonListener implements ActionListener{

/* what to do when a button has been pressed */
public void actionPerformed (ActionEvent aE) {
JButton whichButton = (JButton) aE.getSource();

/* actions performed depending on which button is clicked */
if ("+".equals(whi chButton.getTex t())){
calc.inOperator ("+");
display.setText ("" + calc.getResult( ));

}
else if ("-".equals(whichB utton.getText() )) {
calc.inOperator ("-");
display.setText ("" + calc.getResult( ));

}
else if ("*".equals(whi chButton.getTex t())) {
calc.inOperator ("*");
display.setText ("" + calc.getResult( ));

}
else if ("C".equals(whi chButton.getTex t())) {
calc.inClear();
display.setText ("");
}
else if ("=".equals(whi chButton.getTex t())) {
calc.inEquals() ;
display.setText ("" + calc.getResult( ));


calc.inClear();
}
else {
long t = 0;
Scanner scan = new Scanner(whichBu tton.getText()) ;
t = scan.nextInt();
calc.inDigit(t) ;
display.setText ("" + calc.getCurrent Input());
}

}//end actionPerformed
}//end ButtonListener method

}//end class
[/CODE]







[CODE=java]public class CalcText {

// the calculator we'll be using
private static Calculator c = new Calculator();

/* Main method - performs a simple calculation on the calculator */
public static void main(String[] args) {
// A simple calculation, 50 - 26 =
c.inDigit(5);
c.inDigit(0);
c.inOperator("-");
c.inDigit(2);
c.inDigit(6);
c.inEquals();
System.out.prin tln( "50 - 26 = " + c.getResult());
c.inClear();
}

}

[/CODE]



basically i can operate the calculator however, how can i process one or more of the following input sequences:

3+10= -4 =
3+4=+7=


what should i add??? Cheers!

[r035198x]

1.) Please use code tags when posting code.
2.) Are you talking about implementing the memory function?

[mandy335]

Yes. Cheers! Sorry bout not using tags, am new in this.

[JosAH]

basically i can operate the calculator however, how can i process one or more of the following input sequences:

3+10= -4 =
3+4=+7=

what should i add??? Cheers!

You can think of an artificial variable 'answer' which contains the result of the last
expression (when the = operator is evaluated). This turns your examples into:

3+10= answer-4=
3+4= answer+7=

The 'answer' disappears when a digit is pressed just after the answer is produced.
A boolean variable can handle that (old calculators used that little trick).

kind regards,

Jos