Java, Is it possible to replace Nth line of a file with a string without creating a temp file?

Question

The only way I have managed is to create a temp file to do this, but this is not what I want. Can someone provide an example of how to replace the Nth line of a text file with a string WITHOUT making a temp file.

Thanks in advance =)

Look into RandomAccessFiles (http://docs.oracle.com/javase/tutorial/essential/io/rafs.html). This should let you do what you want. — kufudo, Feb 16 '13 at 00:19
Is the length of the string, in bytes, equal to the length of the existing line, in bytes? — ruakh, Feb 16 '13 at 00:19
@JessicaMcDaniel please use `@` in your comments to answer to somebody — Luiggi Mendoza, Feb 16 '13 at 01:27

score 1 · Answer 1 · edited May 23 '17 at 11:49

You can use RandomAccessFile...this provides read and write to file at same time...so you dont need to create temp file...

Idea is to skip through N-1 th line using readLine..

then count bytes of seventh line and compare with your replaceString bytes...

if replaceStringBytes < seventhLineBytes then replace entire seventh line bytes and continue reading after seventh line and moving the bytes before in file...

if replaceStringBytes > seventhLineBytes then create buffer of difference in bytes and store additional bytes after seventh line... continue filling up the buffer with difference each time you move forward...

here is a thread which will give you some hint...

Java - delete line from text file by overwriting while reading it

Java, Is it possible to replace Nth line of a file with a string without creating a temp file?

1 Answers1