Why can't I read an integer from a text file using a BufferedReader?

Question

I can't read an integer from a text file using a BufferedReader:

BufferedReader br = new BufferedReader(new FileReader("C:/heapsort.txt"));
s = br.readLine();
int x = Integer.parseInt(s);

The code above throws the following exception:

ava.lang.NumberFormatException: null
    at java.lang.Integer.parseInt(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)
    at tester.main(tester.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)

From javadoc "A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached". try adding a check while((str=br.readLine())!=null && str.length()!=0) — Prabhakaran
– Prabhakaran, Commented May 29, 2015 at 17:54

Shriram · Accepted Answer · 2015-05-29 17:51:55Z

1

Make sure that the value read from file is not null and integer. Otherwise you will get the Exception. Because readLine returns the whole line from the file as string

answered May 29, 2015 at 17:51

Shriram

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1 Comment

NafisDroid Over a year ago

Yap file was not saved ...I just forget to save the file.. Thanx

M Sach · Accepted Answer · 2015-05-29 17:54:36Z

1

Looks file is empty. To make sure your covers this case as well handle for null

while((br = br.readLine()) != null) { 
int x = Integer.parseInt(s);
System.out.println(br); 
}

answered May 29, 2015 at 17:54

M Sach

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