Why do I get a "Number Format Exception"?

Question

I have this code and in it there is a function to convert binary to decimal. It sets the text of a JTextArea to the result and appends the result to a different JTextArea. The former works fine but the latter causes the above mentioned exception to appear. This is my code below. Pls help.

JButton numerical = new JButton("BIN->NUM");
    numerical.setFont(small);
    numerical.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            Display.setText(String.valueOf(Integer.parseInt(Display.getText(), 2)));
            try {
                Memory.append(String.valueOf(Integer.parseInt(Display.getText(), 2))); 
                Memory.append("\n");
            } catch (Exception ie) {
                Memory.append(String.valueOf(Integer.parseInt(Display.getText(), 2)));
            }
        }
    });

Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it in the question itself. Questions without a clear problem statement are not useful to other readers. — Jim Garrison, Jun 02 '16 at 17:57
Possible duplicate of [How to avoid Number Format Exception in java?](http://stackoverflow.com/questions/5499523/how-to-avoid-number-format-exception-in-java) — shoover, Jun 02 '16 at 23:12

score 3 · Accepted Answer · edited Jun 02 '16 at 18:00

As you say, the first works fine. At this point

Display.setText(String.valueOf(Integer.parseInt(Display.getText(), 2)));

The input value to parseInt() is in binary form and the conversion works. However the setText() replaces that binary value with the decimal equivalent. Then when you attempt

Memory.append(String.valueOf(Integer.parseInt(Display.getText(), 2)));

the number is in decimal format and the second conversion fails because you specified base 2 and it expects the number to be in binary.

Why do I get a "Number Format Exception"?

1 Answers1