FileInputStream.read(...) 和 RandomAccessFile 的区别

Question

I am new to Random File Access, and I have encountered one issue - as far as I have understood, RandomAccessFile class provides a Random Access file for reading/writing. I can use seek() method to move to preferable position and start reading or wrting, but does not matter in this case. It is completely the random access? But in FileInputStream I have the same ability

read(bute[] byte, int off, int len)

this method provides me reading from some particular place. So, what is the difference? (I guess, InputStream read all file, but just go through all symbols before off position, but it only my guess).

Answer 1

Looking at the documentation of the read method: https://docs.oracle.com/javase/7/docs/api/java/io/FileInputStream.html#read(byte[],%20int,%20int) it states that off is "the start offset in the destination array b". So using this call, you can read the next len bytes from the stream and put them is a certain place in your memory buffer. This does not allow you to skip forward like the seek method of a random access file.

Answer 2

The read method you mention does not let you read from any particular place. It always reads from the "next" position in the stream, where it left off, and it puts the read bytes into the byte array at position off . off is the offset in the output , not the input.