Java Simple Calculator
- by Lahiru Kavinda
I have made this calculator program in Java. This works well only when two numbers are calculated at one time. That means to get the sum of 1+2+3 you have to go this way :
press 1
press +
press 2
press =
press +
press 3
press =
and it calculates it as 6.
But I want to program this so that I can get the answer by:
press 1
press +
press 2
press +
press 3
press =
but this gives the answer 5!!! How to code this so that it works like an ordinary calculator?
Here is my code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class cal1 extends JFrame {
double op1 = 0d, op2 = 0d;
double result = 0d;
char action;
boolean b = false;
boolean pressequal = false;
public cal1() {
makeUI();
}
private void makeUI() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400, 400);
b0 = new JButton("0");
b1 = new JButton("1");
b2 = new JButton("2");
b3 = new JButton("3");
b4 = new JButton("4");
b5 = new JButton("5");
b6 = new JButton("6");
b7 = new JButton("7");
b8 = new JButton("8");
b9 = new JButton("9");
bDot = new JButton(".");
bMul = new JButton("*");
bDiv = new JButton("/");
bPlus = new JButton("+");
bMinus = new JButton("-");
bEq = new JButton("=");
t = new JTextField(12);
t.setFont(new Font("Tahoma", Font.PLAIN, 24));
t.setHorizontalAlignment(JTextField.RIGHT);
numpad = new JPanel();
display = new JPanel();
numpad.add(b7);
numpad.add(b8);
numpad.add(b9);
numpad.add(bMul);
numpad.add(b4);
numpad.add(b5);
numpad.add(b6);
numpad.add(bDiv);
numpad.add(b1);
numpad.add(b2);
numpad.add(b3);
numpad.add(bMinus);
numpad.add(bDot);
numpad.add(b0);
numpad.add(bEq);
numpad.add(bPlus);
numpad.setLayout(new GridLayout(4, 5, 5, 4));
display.add(t);
add(display, BorderLayout.NORTH);
add(numpad, BorderLayout.CENTER);
t.addKeyListener(new KeyAdapter() {
@Override
public void keyTyped(KeyEvent e) {
typeOnt(e);
}
});
b0.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b0pressed(e);
}
});
b1.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b1pressed(e);
}
});
b2.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b2pressed(e);
}
});
b3.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b3pressed(e);
}
});
b4.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b4pressed(e);
}
});
b5.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b5pressed(e);
}
});
b6.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b6pressed(e);
}
});
b7.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b7pressed(e);
}
});
b8.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b8pressed(e);
}
});
b9.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
b9pressed(e);
}
});
bDot.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
bDotpressed(e);
}
});
bPlus.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
bPlusPressed(e);
}
});
bMinus.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
bMinusPressed(e);
}
});
bMul.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
bMulPressed(e);
}
});
bDiv.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
bDivPressed(e);
}
});
bEq.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
bEqpressed(e);
}
});
}
void typeOnt(KeyEvent e) {
e.consume();
}
void b0pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "0");
} else {
t.setText(t.getText() + "0");
}
}
void b1pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "1");
} else {
t.setText(t.getText() + "1");
}
}
void b2pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "2");
} else {
t.setText(t.getText() + "2");
}
}
void b3pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "3");
} else {
t.setText(t.getText() + "3");
}
}
void b4pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "4");
} else {
t.setText(t.getText() + "4");
}
}
void b5pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "5");
} else {
t.setText(t.getText() + "5");
}
}
void b6pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "6");
} else {
t.setText(t.getText() + "6");
}
}
void b7pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "7");
} else {
t.setText(t.getText() + "7");
}
}
void b8pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "8");
} else {
t.setText(t.getText() + "8");
}
}
void b9pressed(ActionEvent e) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "9");
} else {
t.setText(t.getText() + "9");
}
}
void bDotpressed(ActionEvent e) {
if (!t.getText().contains(".")) {
if (b) {
t.setText(null);
b = false;
t.setText(t.getText() + "0.");
} else if (t.getText().isEmpty()) {
t.setText("0.");
} else {
t.setText(t.getText() + ".");
}
}
}
void bPlusPressed(ActionEvent e) {
b = true;
action = '+';
op1 = Double.parseDouble(t.getText());
}
void bMinusPressed(ActionEvent e) {
b = true;
action = '-';
op1 = Double.parseDouble(t.getText());
}
void bMulPressed(ActionEvent e) {
b = true;
action = '*';
op1 = Double.parseDouble(t.getText());
}
void bDivPressed(ActionEvent e) {
b = true;
action = '/';
op1 = Double.parseDouble(t.getText());
}
void bEqpressed(ActionEvent e) {
op2 = Double.parseDouble(t.getText());
doCal();
}
void doCal() {
switch (action) {
case '+': result = op1 + op2; break;
case '-': result = op1 - op2; break;
case '*': result = op1 * op2; break;
case '/': result = op1 / op2; break;
}
t.setText(String.valueOf(result));
}
public static void main(String[] args) {
new cal1().setVisible(true);
}
JButton b0;
JButton b1;
JButton b2;
JButton b3;
JButton b4;
JButton b5;
JButton b6;
JButton b7;
JButton b8;
JButton b9;
JButton bDot;
JButton bPlus;
JButton bMinus;
JButton bMul;
JButton bDiv;
JButton bEq;
JPanel display;
JPanel numpad;
JTextField t;
}
