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I've been learning java for over a year and I'm looking for better ways to learn and I'm trying to get a better idea of where I am as a programmer. I honestly have no clue if my code is good or bad. I'd really appreciate it if you could have a look at my code and point out anything that's wrong with it. The calculator has the same functionality as the windows 7 calculator and it's split into 3 classes.

Edit: Sorry I didnt know we couldn't post external links. Edited it to include the code.

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I've been learning java for over a year and I'm looking for better ways to learn and I'm trying to get a better idea of where I am as a programmer. I honestly have no clue if my code is good or bad. I'd really appreciate it if you could have a look at my code and point out anything that's wrong with it. The calculator has the same functionality as the Windows 7 calculator and it's split into 3 classes.

I've been learning java for over a year and I'm looking for better ways to learn and I'm trying to get a better idea of where I am as a programmer. I honestly have no clue if my code is good or bad. I'd really appreciate it if you could have a look at my code and point out anything that's wrong with it. The calculator has the same functionality as the windows 7 calculator and it's split into 3 classes. Here is the github repository: https://github.com/AlexM9200/Java-Swing-Calculator

I've been learning java for over a year and I'm looking for better ways to learn and I'm trying to get a better idea of where I am as a programmer. I honestly have no clue if my code is good or bad. I'd really appreciate it if you could have a look at my code and point out anything that's wrong with it. The calculator has the same functionality as the windows 7 calculator and it's split into 3 classes.

Edit: Sorry I didnt know we couldn't post external links. Edited it to include the code.

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.script.ScriptException;
import javax.swing.*;
public class Calculator extends JFrame implements Runnable {
private MemoryStore memoryStore = new MemoryStore();
private JTextPane screen;
private JPanel buttonPanel;
private JButton[] numberButtons;
private JButton[] operationButtons;
private String display = "";
private boolean shouldOverwrite = false;
private String[] operationButtonStrings = { "ME", "MR", "MS", "M+", "M-", "←", "C", "+", "-", "*", "/", "√", "x2",
 "±", "%", ".", "1/x", "=" };
public Calculator() {
 super("Java Calculator");
}
@Override
public void run() {
 makeGUI();
}
private void makeGUI() {
 frameSetup();
 screenSetup();
 createNumberButtons();
 createOperationButtons();
 addButtons();
 setVisible(true);
}
private void frameSetup() {
 setSize(300, 300);
 setLocationRelativeTo(null); // Open frame in middle of screen
 setResizable(false);
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private void screenSetup() {
 screen = new JTextPane();
 screen.setBorder(BorderFactory.createBevelBorder(1));
 screen.setEditable(false);
 screen.setFont(new Font("Segoe UI", Font.BOLD, 18));
 add(screen, BorderLayout.NORTH);
}
private void createNumberButtons() {
 MyNumberButtonListener numberButtonListener = new MyNumberButtonListener();
 numberButtons = new JButton[10];
 for (int i = 0; i < 10; i++) {
 numberButtons[i] = new JButton(Integer.toString(i));
 numberButtons[i].addActionListener(numberButtonListener);
 numberButtons[i].setFocusable(false);
 }
}
private void createOperationButtons() {
 MyOperationButtonListener operationButtonListener = new MyOperationButtonListener();
 operationButtons = new JButton[18];
 for (int i = 0; i < 18; i++) {
 operationButtons[i] = new JButton(operationButtonStrings[i]);
 operationButtons[i].addActionListener(operationButtonListener);
 operationButtons[i].setFocusable(false);
 }
}
private void addButtons() {
 buttonPanel = new JPanel();
 buttonPanel.setLayout(new GridLayout(6, 5, 1, 1));
 buttonPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
 for (int i = 0; i < 10; i++) {
 buttonPanel.add(numberButtons[i]);
 }
 for (int i = 0; i < 18; i++) {
 buttonPanel.add(operationButtons[i]);
 }
 buttonPanel.add(new JButton());
 buttonPanel.add(new JButton());
 add(buttonPanel);
}
private class MyNumberButtonListener implements ActionListener {
 @Override
 public void actionPerformed(ActionEvent e) {
 for (int i = 0; i < 10; i++) {
 if (e.getSource() == numberButtons[i]) {
 displayNumber(i);
 break;
 }
 }
 }
}
private void displayNumber(int number) {
 if (shouldOverwrite) {
 screen.setText("" + number);
 shouldOverwrite = false;
 } else {
 display = screen.getText();
 screen.setText(display + number);
 }
}
private class MyOperationButtonListener implements ActionListener {
 @Override
 public void actionPerformed(ActionEvent e) {
 if (e.getSource() == operationButtons[0]) {
 memoryStore.resetStoredValue();
 } else if (e.getSource() == operationButtons[1]) {
 display = screen.getText();
 screen.setText(display + "" + memoryStore.getStoredValue());
 } else if (e.getSource() == operationButtons[2]) {
 if (!screenIsEmpty())
 memoryStore.store(readScreenAsDouble());
 } else if (e.getSource() == operationButtons[3]) {
 if (!screenIsEmpty())
 memoryStore.plusStoredValue(readScreenAsDouble());
 } else if (e.getSource() == operationButtons[4]) {
 if (!screenIsEmpty())
 memoryStore.minusStoredValue(readScreenAsDouble());
 } else if (e.getSource() == operationButtons[5]) {
 backSpace();
 } else if (e.getSource() == operationButtons[6]) {
 clearScreen();
 } else if (e.getSource() == operationButtons[7]) {
 displaySymbol(operationButtons[7].getText());
 } else if (e.getSource() == operationButtons[8]) {
 displaySymbol(operationButtons[8].getText());
 } else if (e.getSource() == operationButtons[9]) {
 displaySymbol(operationButtons[9].getText());
 } else if (e.getSource() == operationButtons[10]) {
 displaySymbol(operationButtons[10].getText());
 } else if (e.getSource() == operationButtons[11]) {
 writeToScreen(CalcUtilities.sqrRoot(readScreenAsDouble()));
 shouldOverwrite = true;
 } else if (e.getSource() == operationButtons[12]) {
 writeToScreen(CalcUtilities.squared(readScreenAsDouble()));
 shouldOverwrite = true;
 } else if (e.getSource() == operationButtons[13]) {
 changeToPlusOrMinus();
 } else if (e.getSource() == operationButtons[14]) {
 displaySymbol(operationButtons[14].getText());
 } else if (e.getSource() == operationButtons[15]) {
 if (!displayHasDecimal())
 displaySymbol(operationButtons[15].getText());
 } else if (e.getSource() == operationButtons[16]) {
 writeToScreen(CalcUtilities.reciprocal(readScreenAsDouble()));
 shouldOverwrite = true;
 } else if (e.getSource() == operationButtons[17]) {
 equalsAction();
 }
 }
}
private double readScreenAsDouble() {
 double result;
 display = screen.getText();
 result = parseDisplayToDouble(display);
 return result;
}
private void writeToScreen(double numToWrite) {
 screen.setText(Double.toString(numToWrite));
}
public double parseDisplayToDouble(String display) {
 double result;
 try {
 result = Double.parseDouble(display);
 } catch (NumberFormatException e) {
 return 0.0;
 }
 return result;
}
private void displaySymbol(String symbol) {
 display = screen.getText();
 screen.setText(display + symbol);
 shouldOverwrite = false;
}
private void clearScreen() {
 screen.setText("");
}
private boolean displayHasDecimal() {
 display = screen.getText();
 if (display.indexOf('.') != -1)
 return true;
 else
 return false;
}
private void equalsAction() {
 display = screen.getText();
 try {
 screen.setText(CalcUtilities.evaluate(display) + "");
 } catch (ScriptException e) {
 screen.setText("Invalid");
 }
 shouldOverwrite = true;
}
private void backSpace() {
 if (!screenIsEmpty()) {
 display = screen.getText();
 screen.setText(display.substring(0, display.length() - 1));
 }
}
private void changeToPlusOrMinus() {
 display = screen.getText().toString();
 if (display.charAt(0) != '-')
 screen.setText("-" + display);
 else
 screen.setText(display.substring(1, display.length()));
 shouldOverwrite = false;
}
private boolean screenIsEmpty() {
 display = screen.getText().toString();
 if (display.equals(""))
 return true;
 else
 return false;
}
}

///

/*
 * Author: Alex Matthews
 * Ireland
 */ 
import javax.script.*;
public class CalcUtilities {
private static ScriptEngineManager mgr = new ScriptEngineManager();
private static ScriptEngine engine = mgr.getEngineByName("JavaScript");
public static double reciprocal(double num) {
 return 1 / num; 
}
public static double squared(double num) {
 return num * num;
}
public static double sqrRoot(double num) {
 return Math.sqrt(num);
}
public static Object evaluate(String equation) throws ScriptException {
 return engine.eval(equation);
}
}

///

/*
 * Author: Alex Matthews
 * Ireland
 */ 
public class MemoryStore {
 private double storedVal = 0.0;
 public void store(double num) {
 storedVal = num;
 }
 public double getStoredValue() {
 return storedVal;
 }
 public void resetStoredValue() {
 storedVal = 0.0;
 }
 public void plusStoredValue(double num) {
 storedVal += num;
 }
 public void minusStoredValue(double num) {
 storedVal -= num;
 }
 
}