CODEWITHSUNDEEP
javastringnullpointerexceptionbufferedreader
gossfunkel
gossfunkel

Reputation: 257

Java NullPointerException even though object exists

I'm getting a NullPointerException on a line where I call a method and pass it a string. I can only assume the string is null.

It was initialised from a BufferedReader readline a few lines before. Here's the relevant code:

FileInputStream tmp = null;
try {
    tmp = new FileInputStream(file);
} catch (FileNotFoundException e) {
    System.err.println("File not found!");
    e.printStackTrace();
    System.exit(1);
}
DataInputStream dis = new DataInputStream(tmp);
BufferedReader br = new BufferedReader(new InputStreamReader(dis));

create();

try {
    data = br.readLine();
} catch (IOException e) {
    System.err.println("First readline failed: " + e);
    System.exit(1);
}
while (!data.equals(null)) {
    process(data);
    ...

and the error:

Exception in thread "main" java.lang.NullPointerException
       at enc.read(enc.java:40)
       at enc.main(enc.java:15)

Upvotes: 1

Views: 1667

Answers (4)

MrSmith42
MrSmith42

Reputation: 10151

while (!data.equals(null)) makes no sense. If data is null you cannot call equals(..)on it.

Replace

while (!data.equals(null))

by

while (data!=null)

Upvotes: 1

Amir Afghani
Amir Afghani

Reputation: 38521

If I had to guess, I think the bug is in:

while (!data.equals(null)) {
   process(data);

try changing it to:

while (data != null) {
    process(data);
}

You can't invoke a method from a null object.

Upvotes: 2

beny23
beny23

Reputation: 35008

Without knowing the line numbers, I would suspect that the following is the culprit:

!data.equals(null)

If data is null, then a NullPointerException will be thrown.

Replace it with:

data != null

Upvotes: 6

C-Otto
C-Otto

Reputation: 5843

Your nullness check itself triggers the NullPointerException. Instead of !data.equals(null) write data != null.

Upvotes: 8

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