CODEWITHSUNDEEP
javafile
Jal
Jal

Reputation: 2312

Does Files.lines read all lines into memory?

In the doc it says

Read all lines from a file as a Stream.

Does that necessary mean that it's loading the entire file? For example:

try (Stream<String> stream = Files.lines(Paths.get("myfilename.txt"))) {
        stream.forEach(x -> {

if myfilename is 100GB , will Files.lines load the entire 100GB?

Upvotes: 13

Views: 4825

Answers (4)

ssindelar
ssindelar

Reputation: 2843

There is an issue with the Spliterator if Files.lines is used with a parallel stream. Than all processed lines will be stored in the Spliterator which makes it unuseable for large files.

Upvotes: 0

tony
tony

Reputation: 21

A new method lines() has been added since 1.8, it lets BufferedReader returns content as Stream.this method does not read all lines into a List, but instead populates lazily as the stream is consumed.when you call for-each,then a new line is reload. hope can help you!

Upvotes: 2

Izruo
Izruo

Reputation: 2276

Well, the link you provided states it already:

Unlike readAllLines, this method does not read all lines into a List, but instead populates lazily as the stream is consumed.

So for every time your for-each block is called, a new line is read.

Upvotes: 9

shmosel
shmosel

Reputation: 50716

No, it doesn't load the entire file into memory. It internally uses a BufferedReader with the default buffer size, repeatedly calling readLine().

Upvotes: 6

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