Why am I getting a nullpointer exception while I'm checking whether an array string is empty?

Question

Why am I getting a nullpointer error at the second if statement below?

I'm checking in that if statement if the array string scores is empty or not, but it always crashes saying nullpointer exception. I also added the LogCat if that helps.

String[] scores;
String times = "";

public void Read() {
    FileInputStream inputStream = null;

    try {

        inputStream = openFileInput("timesfile");

        byte[] reader = new byte[inputStream.available()];

        while (inputStream.read(reader) != -1) {
        }
        times = new String(reader);

    } catch (IOException e) {
        e.printStackTrace();

    } finally {
        if (inputStream != null) {
            try {
                    inputStream.close();
            } catch (IOException e) {
                    e.printStackTrace();
            }

        }

    }

    if (!times.isEmpty() && times != null && times != ""
                    && times.length() != 0) 
    {
        scores = new String(times).split(",");
        Arrays.sort(scores);
    }
    if (scores.length != 0 && scores != null && scores.length >= 4) { //I get a nullpointer exception here!

        better = false;
        if (Integer.parseInt(endTime.split(":")[0]) > Integer
                        .parseInt(scores[0].split(":")[0])) {
            better = true;
        } else if (Integer.parseInt(endTime.split(":")[1]) > Integer
                        .parseInt(scores[0].split(":")[1])) {
            better = true;
        } else if (Integer.parseInt(endTime.split(":")[2]) > Integer
                        .parseInt(scores[0].split(":")[2])) {
            better = true;
        } else {
            better = false;
        }

    }

}

LogCat:

11-16 22:32:21.195: E/AndroidRuntime(28584): FATAL EXCEPTION: Thread-2278
11-16 22:32:21.195: E/AndroidRuntime(28584): java.lang.NullPointerException
11-16 22:32:21.195: E/AndroidRuntime(28584):    at com.example.app.TestActivity$TestView.scoreRead(TestActivity.java:426)
11-16 22:32:21.195: E/AndroidRuntime(28584):    at com.example.app.TestActivity$TestView.over(TestActivity.java:303)
11-16 22:32:21.195: E/AndroidRuntime(28584):    at com.example.app.TestActivity$TestView.run(TestActivity.java:267)
11-16 22:32:21.195: E/AndroidRuntime(28584):    at java.lang.Thread.run(Thread.java:856)

try switching the order to if (times != null && !times.isEmpty() && times != "" — Anthony Ledesma
– Anthony Ledesma, Commented Nov 16, 2012 at 21:41
This is line 426: if (scores.length != 0 && scores != null && scores.length >= 4) { — user1816451
– user1816451, Commented Nov 16, 2012 at 21:42
always check for a null object before any properties on the object — Anthony Ledesma
– Anthony Ledesma, Commented Nov 16, 2012 at 21:43

PCM · Accepted Answer · 2012-11-16 22:38:44Z

3

can you try with keeping the times != null in the left most. The order of operation is from left to right.

if (times != null && !times.isEmpty() && times != "" && times.length() != 0)

EDIT: and yes @Simon is right.. times != "" should be !times.equal("")

But anyway you are already checking !times.isEmpty() so you don't need that piece at all.

This should do:

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

edited Nov 16, 2012 at 22:38

answered Nov 16, 2012 at 21:46

PCM

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Comments

CQM · Accepted Answer · 2012-11-16 21:41:09Z

1

do if(times!= null) first

then nested in that do !times.isEmpty()

isEmpty() checks to see if the length of the string is zero or not. Not if it is null or not. length of 0 is "", not null

the same principle applies if it is another string that is being checked

answered Nov 16, 2012 at 21:41

CQM

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1 Comment

dymmeh Over a year ago

^ This. You can just use if(!TextUtils.isEmpty(times)) instead

xagyg · Accepted Answer · 2012-12-01 17:27:53Z

1

Replace

if (scores.length != 0 && scores != null && scores.length >= 4) {

with

if (scores != null && scores.length >= 4) {

Replace

if (!times.isEmpty() && times != null && times != "" && times.length() != 0)

with

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

i.e. put null checks at front of condition and remove unnecessary guards.

answered Dec 1, 2012 at 17:27

xagyg

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Comments

Simon · Accepted Answer · 2012-11-16 21:47:37Z

0

This is not a safe check.

times != ""

The equality operator for String tests whether the 2 Strings are the same object. Instead, use

!times.equal("")

!= might work some times is "" because Java "interns" strings and by chance, they might be the same object but you should not rely on that.

answered Nov 16, 2012 at 21:47

Simon

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Comments

Sam · Accepted Answer · 2012-11-16 21:52:51Z

0

Your question and your comment don't match up, but regardless of whether you are checking scores or times you must check if they are null first. (Otherwise you will see the NPE.)

Use:

if (times != null && !times.isEmpty() && times != "" && times.length() != 0)

And:

if (scores != null && scores.length != 0 && scores.length >= 4) {

Why am i getting a nullpointer error at the second if statement below?

A NullPointerException occurs when you try to call a method on variable that is null. So if scores is null, this code scores.length is trying to call null.doSomething(). You cannot ask nothing to do something.

answered Nov 16, 2012 at 21:52

Sam

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Comments

Eugene · Accepted Answer · 2012-11-16 22:25:04Z

0

actually your scores array is initialized only if

!times.isEmpty() && times != null && times != "" && times.length() != 0

is true. It happened so that it is not true :). And there is no sense in invoking method on times and than compare it for null. However no NPE is thown here, so let's omit that.

!times.isEmpty is the same as times.legth != 0;

times != "" is always true as soon as it is initialized with 'new' operaton and is not interned.

So all the condition is equal to (time is not null as you can see)

!times.isEmpty

Anyway you should check on null before the other checks that involves method invocation on checked object.

edited Nov 16, 2012 at 22:25

answered Nov 16, 2012 at 22:14

Eugene

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Comments

matheuslf · Accepted Answer · 2012-11-16 22:55:19Z

0

The variable times not is null. She was not initialized with null value but empty value.

The NullPointerException can be found in the row 426 in TestActivity class. I think that row is:

if (scores.length != 0 && scores != null && scores.length >= 4) {

So, if you look better into your code, the scores variables is null because the condition above is wrong.

Change your code for this:

if (!times.isEmpty()) 
{
     scores = times.split(",");
     Arrays.sort(scores);
}
if (scores != null && scores.length > 0) {

   ...

}
else {

   System.err.println("There isn't score");
}

answered Nov 16, 2012 at 22:55

matheuslf

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