Why does my if else not function properly?

Question

Why does my if-else block not detect that gamma is null? Here is my code. It is a Spreadsheet application and this is the save function which loops through all of the cells in the table and writes it to a file. Here is my code:

public void Save () {
        String FileName = JOptionPane.showInputDialog("Please enter the name for your file:");

        if (FileName == null) {
            System.err.println("You didn't enter anything");
        } else {
            int rows = Table.getRowCount();
            int columns = Table.getColumnCount();
            int alpha = 0;
            int beta = 1; 
            choicer.setCurrentDirectory(new java.io.File("Desktop"));
            choicer.setDialogTitle("Save Document");
            choicer.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
            choicer.setAcceptAllFileFilterUsed(false);
            if (choicer.showSaveDialog(new JPanel()) == JFileChooser.APPROVE_OPTION) {
                dir = String.valueOf(choicer.getSelectedFile());
            }
            File f = new File(dir + "\\" + FileName + ".txt");
            try {
                fos = new FileOutputStream(f);
                osw = new OutputStreamWriter(fos);
                w = new BufferedWriter(osw);
                for (alpha = 0; alpha <= rows - 1; alpha++) {
                    for (beta = 1; beta < columns; beta++) {
                        String gamma = String.valueOf(Table.getValueAt(alpha, beta));
                        if (gamma != null) {
                            w.write("<%! " + gamma + " !%> ");
                        } else {
                            w.write(" <%! |^-^| !%> ");
                        }                           
                    }
                    w.write("\n");
                }
            } catch (IOException e) {
                System.err.println("Some prob dude. Too big for me"); 
            } finally {
                try {
                    w.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

I tried the link given by the duplicate thing but that doesn't solve my problem. If I do if(gamma != null && !(gamma.isEmpty)) then only null is written to the file as the value of gamma.

Maybe, gamma is not null... but empty, isn it? Check as follows: "gamma != null && !gamma.isEmpty()" — guipivoto, Jul 06 '16 at 16:13
Perhaps you could reduce your code sample to the salient line, and include details re. Table.getValueAt() ? — Brian Agnew, Jul 06 '16 at 16:13
@BrianAgnew I added all code just in case someone might want extra validastion — Adit Kirtani, Jul 06 '16 at 16:15
@RahulSrinath that is because on the line before you call `String.valueOf` on a variable whose value is `null`. `gamma` in this case is not `null`, but becomes the string `"null"`. — Jeen Broekstra, Jul 09 '16 at 17:20

score 0 · Accepted Answer · answered Jul 06 '16 at 16:14

0

Maybe, gamma is empty but not null:

Change

if (gamma != null)

To

if (gamma != null && !gamma.isEmpty())

answered Jul 06 '16 at 16:14

guipivoto

18,327
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If gamma == " ", it isn't considered empty right? – Adit Kirtani Jul 06 '16 at 16:22
Hummm. I need to check... initially. I believe that a space is not a empty string – guipivoto Jul 06 '16 at 16:28
1

The documentation for `isEmpty` indicates that it's basically shorthand for checking if the length of the string is equal to zero - so no, strings consisting of a single whitespace aren't considered empty because they have a non-zero length. – JonK Jul 06 '16 at 16:31
@JonK Thank you for clarifying this point! Thank you – guipivoto Jul 06 '16 at 16:45
@GuilhermeP now everything is considered null – Adit Kirtani Jul 06 '16 at 17:24

score 0 · Answer 2 · answered Jul 06 '16 at 16:18

There are only three things that I can think of that would cause this. I will get to those in a second. First, what IDE are you using? Do you have the ability to set a breakpoint and watch variables? This will help you in troubleshooting the following. 1. Can you ensure that the first for loop hits? 2. Then, make sure you are getting in the second for loop. 3. Finally, what is the actual value of the string gamma? This is where you need a breakpoint and to inspect that variable when you are expecting it to be null. Likely you will see it is not. That is of course, assuming that your for loops are even letting you get there.

Hope this helps!

I also agree with @Guilherme P as well. This could very well be the cause too. — Michael Bedford, Jul 06 '16 at 16:19

Why does my if else not function properly?

2 Answers2