How to read text file[.log file] every 1Mb

Question

I have a large log file and I want to read it 1Mb one by one .

Example.I have 100Mb text file and I want to read 1Mb at a time. That need 100 times.

Any relevant Ideas ?

Answer 1

You can pass your file to an InputStream and the call the function read(byte[] b, int off, int len) and pass the total amount of bytes to be read in len and pass the right offset to off, or just use read() to read one byte of the InputStream and pass a loop around this statment

for(int i = 0; i < 1048576; i++) 
{ 
    input.read(); 
    //do something with the input
}

Answer 2

The simplest approach is if you do not have to read 1MB sharp, i.e. you have to just read file line by line and when it exceeds 1M stop. In this case just count the bytes you have read: 1

BufferedReader reader = new BufferedReader(new InputStremReader(new FileInputStream(myfile)));

String line = null;
int bytesCount = 0;

while((line = reader.readLine()) != null) {
    // process the line
    bytesCount += line.getBytes().length;
    if (bytesCount > 1024*1024) {
        // 1MB reached. Do what you need here. 
    }
}

If however you need 1M sharp the task is a little bit more complicated because you still want to use convenient tools for text reading like BufferedReader. In this case create your own input stream that counts bytes and wraps other input stream. Once the limit is achieved your stream should return -1 as a marker of EOF. However it should implement method reset() that signals it to continue reading. The implementation will take a couple of minutes, so I am leaving it to you as an exercise.