I am trying to code a simple calculator like the one you would see in windows (non-scientific). I can not for the life of me figure out how to properly change the text after pressing an operator but still see the original entry that wont change until the next digit is pressed, have the equals key do the same operation if used multiple times (ie: 5+5 = 10 +5 = 15), and when I input a digit that is the same (5+5) it won't accept the second digit. I know I am very close and am probably missing a certain boolean that could allow my code to work properly, but Im not sure where to look. Thanks for any help.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class JCalculator extends JFrame implements ActionListener {
/** intialize the jlabel, jbutton, string that makes the buttons and jpanel that will hold the buttons
*
*/
private JTextField display = new JTextField("0", SwingConstants.RIGHT);
private JPanel buttonPanel = new JPanel();
private JPanel displayPanel = new JPanel();
private JButton newButton, divButton, multiButton, equalsButton, clearButton, plusButton, minusButton;
private String[] arrayButtons = {"7","8", "9", "/", "4", "5", "6", "x", "1", "2", "3", "-", "0","C", "=", "+"};
private int operand = 0;
private int firstInput = 0, secondInput = 0, answer = 0;
JCalculator() {
/** creates the jframe */
JFrame jfrm = new JFrame("Calculator");
/** sets the size of the jfrm and then positions it in the center of screen */
jfrm.setSize(480, 300);
jfrm.setLocationRelativeTo(null);
/** sets the program to close on exit */
jfrm.setDefaultCloseOperation(jfrm.EXIT_ON_CLOSE);
/** ImageIcon img = new ImageIcon(JCalculator.png);
*
*/
/**sets initial layout to border */
jfrm.setLayout(new BorderLayout());
/** makes a panel named display that holds the Jtext display
* enables it and justifies it right
*/
displayPanel.setLayout(new BorderLayout());
displayPanel.add(display, BorderLayout.CENTER);
display.setHorizontalAlignment(JTextField.RIGHT);
display.setEnabled(false);
/** makes a panel for buttons that is a grid layout
*
*/
buttonPanel.setLayout(new GridLayout(4,4));
/** makes a loop to make all of the 16 buttons for the calculator
* the operands all have their own specific buttons
*/
for (int i = 0; i < arrayButtons.length; i++) {
if (arrayButtons[i].equals("/")) {
divButton = new JButton(arrayButtons[i]);
divButton.addActionListener(this);
buttonPanel.add(divButton);
} else if (arrayButtons[i].equals("x")) {
multiButton = new JButton(arrayButtons[i]);
multiButton.addActionListener(this);
buttonPanel.add(multiButton);
} else if (arrayButtons[i].equals("=")) {
equalsButton = new JButton(arrayButtons[i]);
equalsButton.addActionListener(this);
buttonPanel.add(equalsButton);
} else if (arrayButtons[i].equals("C")) {
clearButton = new JButton(arrayButtons[i]);
clearButton.addActionListener(this);
buttonPanel.add(clearButton);
} else if (arrayButtons[i].equals("+")) {
plusButton = new JButton(arrayButtons[i]);
plusButton.addActionListener(this);
buttonPanel.add(plusButton);
} else if (arrayButtons[i].equals("-")) {
minusButton = new JButton(arrayButtons[i]);
minusButton.addActionListener(this);
buttonPanel.add(minusButton);
} else {
newButton = new JButton(arrayButtons[i]);
newButton.addActionListener(this);
buttonPanel.add(newButton);
}
}
/** adds the two panels to the jfrm
* sets jfrm visibility to true
* sets equalsButton to the default button
*/
jfrm.add(displayPanel, BorderLayout.NORTH);
jfrm.add(buttonPanel, BorderLayout.CENTER);
jfrm.getRootPane().setDefaultButton(equalsButton);
jfrm.setVisible(true);
}
public void actionPerformed(ActionEvent ae) {
String s = ae.getActionCommand();
char stringCheck = s.charAt(0);
if (answer == Integer.parseInt(display.getText())) {
display.setText("0");
}
if (Character.isDigit(stringCheck) && display.getText().length() < 8) {
if (display.getText().equals("0")) {
display.setText(s);
} else {
display.setText(display.getText().concat(s));
}
} if (s.equals("+")){
answer = Integer.parseInt(display.getText());
operand = 1;
} if (s.equals( "-")){
answer = Integer.parseInt(display.getText());
operand = 2;
} if (s.equals("x")){
answer = Integer.parseInt(display.getText());
operand = 3;
} if (s.equals("/")){
answer = Integer.parseInt(display.getText());
operand = 4;
} if (s.equals("C")){
firstInput = 0;
secondInput = 0;
answer = 0;
operand = 0;
display.setText("0");
} if (s.equals("=")){
switch(operand){
case 1:
answer += Integer.parseInt(display.getText());
display.setText(Integer.toString(answer));
break;
case 2:
answer -= Integer.parseInt(display.getText());
display.setText(Integer.toString(answer));
break;
case 3:
answer *= Integer.parseInt(display.getText());
display.setText(Integer.toString(answer));
break;
case 4:
if(Integer.parseInt(display.getText()) > 0 || Integer.parseInt(display.getText()) < 0) {
answer /= Integer.parseInt(display.getText());
display.setText(Integer.toString(answer));
break;
} else {
display.setText("Div by 0");
}
}
if(answer > 100000000 || answer < -100000000){
display.setText("Overlow");
}
}
}
public static void main (String [] args){
/**
* run program
*/
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new JCalculator();
}
});
}
}
