Reading more than 5GB of log data in milliseconds

I have Unix server location where the logs get stored and file size is very large (more than 5GB). I would like to read the content from the file and store in an ArrayList or any Java buffer. I have written Java code using JSCH API which reads line by line takes more than 20 mins, but I would like it to run in milliseconds. After which I need to apply Java RegEx pattern on the copied content to further process.