Reading a file while it is being written

Question

Overview

• Thread 1 Tries to write some data to a file continuously
• Thread 2 Tries to read from the same file continuously to parse and process data (Read only)

Problem:

• In thread 2, the file size remains constant (this does not refresh as Thread 1 tries to write data to the file) and therefore, I am not able to parse beyond the initial file size.

Things tried

• FileInputStream: Tried to read from an input stream, the file size stays at a constant value (122924 bytes) and never increases
• RandomAccessFile: Same result as above, the file size stays constant (122924 bytes), tried r/rw modes
• FileChannel: Tried working on a Channel from a FileInputStream, same result as above

Answer 1

You need to lock when you write or read your file. This way only one thread can access the file.

Here is the official android website explaining a lock:

http://developer.android.com/reference/java/util/concurrent/locks/Lock.html

Here is an example using a lock:

https://stackoverflow.com/a/3392615/2767703

You can also use synchronized to lock an object, here is it explained:

Java Synchronization