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POHow do I get the buttons on my calculator to actually do equations?
 

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  1. POHow do I get the buttons on my calculator to actually do equations?
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    <p>I wanted to make a small calculator project for fun to test out my new GUI knowledge with Java Swing API. I created the GUI, but there's a crucial part missing: The math! My Question is, how do I add functionality to each of these buttons? In simpler terms: How do I make the buttons add something to the text box(2+2) when the user clicks the buttons, and then have the system actually add the numbers together and display them for the user?</p> <p>Here's the code: </p> <pre><code>package calculatorPack; import java.awt.BorderLayout; import java.awt.Color; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextArea; import javax.swing.UIManager; public class basicCalculatorDesign { public static void main(String[] args) { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Exception e) { } basicCalculatorDesign calc = new basicCalculatorDesign(); calc.start(); } JTextArea input = new JTextArea(); String[] operators; int[] numbers; public void start() { JFrame frame = new JFrame(); JPanel panel = new JPanel(); JButton one = new JButton("1"); JButton two = new JButton("2"); JButton three = new JButton("3"); JButton four = new JButton("4"); JButton five = new JButton("5"); JButton six = new JButton("6"); JButton seven = new JButton("7"); JButton eight = new JButton("8"); JButton nine = new JButton("9"); JButton zero = new JButton("0"); JButton plus = new JButton("+"); JButton minus = new JButton("-"); JButton divide = new JButton("/"); JButton multiply = new JButton("*"); JButton sqrt = new JButton("SqRt"); JButton percentage = new JButton("%"); JButton equals = new JButton("="); // work on this JLabel label = new JLabel("Basic Calculator"); frame.getContentPane().add(BorderLayout.NORTH, label); frame.getContentPane().add(BorderLayout.SOUTH, input); panel.setBackground(Color.BLUE); panel.setLayout(new GridBagLayout()); JPanel panel2 = new JPanel(); panel2.setLayout(new BoxLayout(panel2, BoxLayout.Y_AXIS)); panel2.setBackground(Color.RED); frame.getContentPane().add(BorderLayout.EAST, panel2); frame.getContentPane().add(BorderLayout.CENTER, panel); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); frame.setSize(210, 260); GridBagConstraints right = new GridBagConstraints(); right.anchor = GridBagConstraints.WEST; GridBagConstraints left = new GridBagConstraints(); left.anchor = GridBagConstraints.EAST; GridBagConstraints middle = new GridBagConstraints(); middle.anchor = GridBagConstraints.CENTER; right.gridwidth = GridBagConstraints.REMAINDER; right.fill = GridBagConstraints.HORIZONTAL; // add buttons panel.add(one, left); panel.add(two, middle); panel.add(three, right); panel.add(four, left); panel.add(five, middle); panel.add(six, right); panel.add(seven, left); panel.add(eight, middle); panel.add(nine, right); panel.add(zero, right); panel2.add(equals); panel2.add(plus); panel2.add(minus); panel2.add(divide); panel2.add(multiply); panel2.add(sqrt); panel2.add(percentage); //integrate buttons one.addActionListener(new ButtonListener()); two.addActionListener(new ButtonListener()); three.addActionListener(new ButtonListener()); four.addActionListener(new ButtonListener()); five.addActionListener(new ButtonListener()); six.addActionListener(new ButtonListener()); seven.addActionListener(new ButtonListener()); eight.addActionListener(new ButtonListener()); nine.addActionListener(new ButtonListener()); zero.addActionListener(new ButtonListener()); equals.addActionListener(new OperatorListener()); } class ButtonListener implements ActionListener { public void actionPerformed(ActionEvent e) { JButton source = (JButton)e.getSource(); input.replaceSelection(source.getActionCommand()); } } class OperatorListener implements ActionListener { public void actionPerformed(ActionEvent e) { JButton source2 = (JButton)e.getSource(); input.replaceSelection(source2.getActionCommand()); } } // I need THIS to do math. class EqualsListener implements ActionListener { public void actionPerformed(ActionEvent e) { } } } </code></pre>
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      1. POHow do I get the buttons on my calculator to actually do equations?
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    1. COAnd what exactly is the problem. You posted a lot of UI code which is irrelevant. Are you saying you can't make a sum in java of two integers ?
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      1. USRobin
    2. CO@Robin Modified the question.
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      1. POHow do I get the buttons on my calculator to actually do equations?
      1. UShasherr
    3. CO1) *"just one last thing"* Famous Last Words. ;) 2) For the calculations, I'd cheat & use the `ScriptEngine`. Example [here](http://stackoverflow.com/a/7441804/418556).
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      1. POHow do I get the buttons on my calculator to actually do equations?
      1. USAndrew Thompson
 

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