Add a calculator using swing API - java.

GUI_calculator/mohit17067/README.md

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+# Calc
+A simple calculator app in Java, for CSE201 refresher module.
+
+### Instructions to run:
+* Simply 'Run' if using Eclipse. You can change the main class in the run configuration.
+* Compile using `javac *.java` from terminal, and run using `java LoginFrame`.
+
+**Update**: I have added a login page as an example of how to use JTextField effectively.

GUI_calculator/mohit17067/src/CalcFrame.java

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+import java.awt.Color;
+import java.awt.GridLayout;
+
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JPanel;
+import javax.swing.border.EmptyBorder;
+
+public class CalcFrame extends JFrame {
+
+	private JButton resultArea;
+
+	public CalcFrame() {
+		setSize(300, 400);
+		setDefaultCloseOperation (EXIT_ON_CLOSE);
+		setLayout (new GridLayout(3, 1));
+
+		resultArea = new JButton ("");
+		resultArea.setEnabled(false);
+		resultArea.setBackground(Color.WHITE);
+
+		add (resultArea);
+		resultArea.setBorder(new EmptyBorder(10, 10, 10, 10));
+
+		JPanel numPanel = new NumberPanel(this);
+		numPanel.setBorder(new EmptyBorder(10, 10, 10, 10));
+		add (numPanel);
+
+		JPanel opPanel = new OperationPanel(this);
+		opPanel.setBorder(new EmptyBorder(10, 10, 10, 10));
+		add (opPanel);
+
+		setVisible(true);
+	}
+
+	public void writeDisplay (String expression) {
+		resultArea.setText(expression);
+	}
+
+	public String readDisplay () {
+		return resultArea.getText();
+	}
+
+	public void evaluateExpression () {
+		String expression = readDisplay();
+		double result = 0;
+		char operator = expression.charAt(1);
+		int operand1 = expression.charAt(0) - '0', operand2 = expression.charAt(2) - '0';
+		if (operator == '+') {
+			result = operand1 + operand2;
+		}
+		else if (operator == '-') {
+			result = operand1 - operand2;
+		}
+		else if (operator == 'x') {
+			result = operand1 * operand2;
+		}
+		else if (operator == '/') {
+			result = operand1 / operand2;
+		}
+
+		writeDisplay(Double.toString(result));
+	}
+
+	//public static void main(String[] args) {
+	//	JFrame calcFrame = new CalcFrame();
+	//}
+}

GUI_calculator/mohit17067/src/LoginFrame.java

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+import java.awt.GridLayout;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.JPasswordField;
+import javax.swing.JTextField;
+import javax.swing.border.EmptyBorder;
+
+public class LoginFrame extends JFrame implements ActionListener {
+	private JTextField useridField;
+	private JPasswordField passwordField;
+	JFrame nextFrame;
+
+	public LoginFrame() {
+		setSize(300, 400);
+		setDefaultCloseOperation (EXIT_ON_CLOSE);
+
+		setLayout (new GridLayout(5, 1, 10, 10));
+
+		JLabel useridLabel = new JLabel("User ID");
+		useridLabel.setBorder(new EmptyBorder(10, 10, 10, 10));
+		add (useridLabel);
+
+		useridField = new JTextField();
+		useridField.setEditable(true);
+		useridField.setBorder(new EmptyBorder(10, 10, 10, 10));
+		add(useridField);
+
+		JLabel passwordLabel = new JLabel("Password");
+		passwordLabel.setBorder(new EmptyBorder(10, 10, 10, 10));;
+		add (passwordLabel);
+
+		passwordField = new JPasswordField(20);
+		passwordField.setEditable(true);
+		passwordField.setBorder(new EmptyBorder(10, 10, 10, 10));
+		add(passwordField);
+
+		JButton loginButton = new JButton("Login");
+		loginButton.addActionListener(this);
+		loginButton.setBorder(new EmptyBorder(10, 10, 10, 10));
+		add(loginButton);
+
+		setVisible(true);
+	}
+
+	public void actionPerformed(ActionEvent e) {
+		if (checkCredentials()) {
+			nextFrame = new CalcFrame();
+		}
+	}
+
+	private boolean checkCredentials() {
+		final String userid = useridField.getText().trim();
+		final String password = passwordField.getText().trim();
+		return (userid.equals("Ganesh") && password.equals("Gaitonde"));
+	}
+
+	public static void main(String[] args) {
+		JFrame loginFrame = new LoginFrame();
+	}
+}

GUI_calculator/mohit17067/src/NumberPanel.java

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+import java.awt.GridLayout;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+
+import javax.swing.JButton;
+import javax.swing.JPanel;
+
+public class NumberPanel extends JPanel {
+	private CalcFrame current_calc_state;
+
+	public NumberPanel (CalcFrame c) {
+		current_calc_state = c;
+
+		setLayout(new GridLayout(3, 3, 10, 10));
+
+		for (int i = 1; i < 10; i++) {
+
+			final int num = i;
+			JButton NumButton = new JButton (Integer.toString (num));
+
+			NumButton.addActionListener (new ActionListener () {
+				@Override
+				public void actionPerformed (ActionEvent e) {
+					current_calc_state.writeDisplay (current_calc_state.readDisplay() + Integer.toString(num));
+				}
+			});
+
+			add (NumButton);
+		}
+
+		setVisible(true);
+	}
+}

GUI_calculator/mohit17067/src/OperationPanel.java

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+import java.awt.GridLayout;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+
+import javax.swing.JButton;
+import javax.swing.JPanel;
+
+public class OperationPanel extends JPanel {
+private CalcFrame current_calc_state;
+
+	private final String opers[] = {"+", "-", "x", "/", "=", "CLR"};
+
+	public OperationPanel (CalcFrame c) {
+		setLayout(new GridLayout(2, 3, 10, 10));
+
+		current_calc_state = c;
+
+		for (int i = 0; i < opers.length; i++) {
+
+			final String op = opers[i];
+			JButton OpButton = new JButton (op);
+
+			OpButton.addActionListener (new ActionListener () {
+
+				@Override
+				public void actionPerformed (ActionEvent e) {
+					if (op == "=") {
+						current_calc_state.evaluateExpression();						
+					}
+					else if (op == "CLR"){
+						current_calc_state.writeDisplay ("");
+					}
+					else {
+						current_calc_state.writeDisplay (current_calc_state.readDisplay() + op);
+					}
+				}
+			});
+
+			add (OpButton);
+		}
+
+		setVisible(true);
+	}
+}