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All possible reasons for readline() to be null

Code piece:
HttpURLConnection url = new HttpURLConnection(new URL("myurl"));
InputStream connInputStream = null;
try
{
connInputStream = conn.getInputStream();
BufferedReader in = new BufferedReader(new InputStreamReader(connInputStream));
boolean matchFound = false;
String strLine = in.readLine();
}
...
In this code piece I get strLine = null, Which means in.readLine is null.
What are the possible reasons that in.readline can come as null.
This code piece does not throw any null pointer exception.
Can this case arise because of the time lag in reading url source to the stream ?

There is only one reason: you've reached the end of the underlying stream. What the end of stream is depends on the underlying stream implementation.

getInputStream() is not returning readable information

My homework assignment is to call a .jar from within a java program but I can't get the input stream to return the results into something readable. Here is what I did first:
InputStream in = proc.getInputStream();
System.out.println(in);
But that didn't work, and I found some different variation:
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
System.out.println(input);
But that didn't work either, both scenarios it returned something like this: java.io.BufferedReader#2ce908. How can I get it to return a readable output?
EDIT: This is a java program receiving the output from another java program. The program that the user starts is called Translate.java which takes in English words and passes them as command line arguments using the Runtime.getRuntime().exec("java -jar Dictionary.jar"+) command. I was told to use the getInputStream() in Translate.java to receive the output from the Dictionary.java program.

A stream is not text; it is a thing that reads a file for you. You have to call readLine:
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
String s = null;
while ((s = input.readLine()) != null) { // it returns null at the end of the file
System.out.println(s);
}

Looping over InputStream truncating data

So this is a very simple problem with a simple solution that I'm just not seeing:
I'm trying to get a list of data through an InputStream, looping until I reach the end of the stream. On each iteration, I print the next line of text being passed through the InputStream. I have it working but for one small problem: I'm truncating the first character of each line.
Here's the code:
while (dataInputStream.read() >= 0) {
System.out.printf("%s\n", dataInputReader.readLine());
}
And the output:
classpath
project
est.txt
Now, I know what's going on here: the read() call in my while loop is taking the first char on each line, so when the line gets passed into the loop, that char is missing. The problem is, I can't figure out how to set up a loop to prevent that.
I think I just need a new set of eyes on this.

readLine for DataInputStream is deprecated. You may try wrapping it with a BufferedReader:
try
{
String line;
BufferedReader bufferedReader = new BufferedReader( new InputStreamReader( dataInputStream ) );
while( (line = bufferedReader.readLine()) != null )
{
System.out.printf("%s\n", line);
}
}
catch( IOException e )
{
System.err.println( "Error: " + e );
}
Also, I`m not sure, that it is a good idea to use available() due to this specification:
* <p>Note that this method provides such a weak guarantee that it is not very useful in
* practice.

Use one BufferedReader and InputStreamReader, here is one example:
InputStream in=...;
BufferedReader br = new BufferedReader(new InputStreamReader(in));
while (br.ready()) {
String line = br.readLine();
}

dataInputStream.read() reads the first character of the InputStream, the same as dataInputReader.readLine() reads the complete next line. Every read character or line is then gone. you can use the dataInputStream.available() to check if the InputStream has data available.
That should print the correct output:
while (dataInputStream.available()) {
System.out.printf("%s", dataInputReader.read());
}

String line;
while ((line = dataInputReader.readLine()) != null) {
System.out.println(line);
}

Java - printing lines from buffered reader

I'm writing an InputStream that supplies lines from a file in constant intervals. I used BufferedReader before, but ran into buffering issues with it (wasn't getting anything until the entire file was read), and speed isn't an issue anyways (the intervals are something like every second, or every half second - along those lines). Is there a class with a readLine method like in BufferedReader, except unbuffered?
(Edit: I just checked - my class seems to work, apparently the problem was with the output)
Here's the code where I used the stream (OnlineDataSimulator). I already checked, the stream does exactly what I want, so apparently I'm doing something wrong with the output. (The actual problem is, I want output to occur every X milliseconds - X being the second parameter to OnlineDataSimulator. What happens when I run this code is, that I first get an X*lines wait and then the entire output at once instead.)
System.out.println("Testing:");
PrintStream fout = new PrintStream(new FileOutputStream("testfile"));
for(int i=0; i<20; ++i) {
fout.println(i);
}
fout.close();
BufferedReader fin = new BufferedReader(new InputStreamReader(
new OnlineDataSimulator("testfile",250)));
String line;
while((line=fin.readLine())!= null){
System.out.println(line);
System.out.flush();
}
fin.close();
(new File("testfile")).delete();

Try it this way.... This worked for me..
File f = new File("path");
FileReader fr = new FileReader(f);
BufferedReader br = new BufferedReader(fr);
String s = null;
while ((s=br.readLine())!=null)
{
System.out.println(s);
}

No, there is no other non-buffered option.
A solution would be to write your own Reader which has a InputStreamReader as an underlying stream and in the readLine() method you should call read() of the underlying input stream reader until "\n" is found. Aggregate all these and return them as a string.

If you don't want to have a real buffer but want to use the functionality of BufferedReader you could initialize it with buffer size 1. As you commented that speed isn't an issue maybe is the most reliable solution.
new BufferedReader(reader, 1)
public BufferedReader(Reader in, int sz)
and you can check the readLine() method source code here, in case you want to implement your own.

Read the first line in a stream and remove it from the stream

I have 2 classes who must read an InputStream, the first one should only interpret the first line of the stream BUT the first line should be removed from the stream so that class B can interpret everything after the first line. Which doesn't work when I pass my InputStream to a BufferedReader and do a readLine().
I know I could do a read on the stream until I've encountered a \b but maybe a more proper solution exists to do the job?
// Reads the first line from the stream and everything else
public String retrieveFileNameFromTheFirstLineInInputStream(InputStream in) throws IOException {
InputStreamReader isReader = new InputStreamReader(in);
BufferedReader reader = new BufferedReader(isReader);
return reader.readLine();
}

You can't remove something from an InputStream, you just can read from it. Don't use the BufferedReader to read the line, because it surely will read much more than the first line from the InputStreamReader (to fill its buffer) which itself reads from the InputStream.
I'd suggest to read using the InputStreamReader until the end of the line is reached, then pass the InputStream instance to your code which should read it.
BTW, you always should specify the encoding used by the InputStreamReader, otherwise the system encoding will be used to convert the bytes from the InputStream to characters which can differ on different machines.

I believe even InputStreamReader can buffer input, so Mike L's answer can miss input.
It's awkward, but you could use ReaderInputStream from Apache commons-io. So:
BufferedReader reader = new BufferedReader(
new InputStreamReader(in));
String firstLine = reader.readLine();
InputStream in2 = new ReaderInputStream(reader);
// continue with in2 ..