Question

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)

Answer 1

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