how much size java string variable can hold

Question

I'm having a file containing one single line data. And the size of file is 300 MB.

This file's data am reading whole as one string and storing into one string variable. Then I'm using that variable for my lookups.

So my question is Is java string variable can hold this much heavy string ?

I think memory issue can happen ..but need suggestions.

Please give your suggestions.

Thanks !!

Suggestions for what? It is not clear what you are asking at all. — rmlan, Dec 07 '16 at 18:29
You'll end up with 2 bytes per UTF-16 code unit... if your file is all ASCII for example, you'll have a 600MB string in memory (at best - depending on how you're reading the file, the underlying `char[]` could easily be bigger, in the same way that an `ArrayList` has spare capacity usually). — Jon Skeet, Dec 07 '16 at 18:30
Yes, a Java String can store a String this large. Yes, you may run out of heap space. There are command line options that let you specify a maximum amount of heap space when you start the JVM. Is that what you're looking for? — Dawood ibn Kareem, Dec 07 '16 at 18:30
My answer to this question http://stackoverflow.com/a/41024966/57695 — Peter Lawrey, Dec 07 '16 at 18:45

BlackHatSamurai · Accepted Answer · 2016-12-07T18:35:55.590

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Java strings can only hold 2147483647 (2^31 - 1) characters (depending on your JVM). So if your string is bigger than that, you will have to break up the string. You could break up the string and store each value in an array, or a hash map, or any viable data structure.

edited Dec 07 '16 at 18:35

answered Dec 07 '16 at 18:31

BlackHatSamurai

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This is the theoretical limit however the actual limit is slightly less on some JVMs due to how arrays are implemented. e.g. Integer.MAX_VALUE-1 or -3. btw +1 – Peter Lawrey Dec 07 '16 at 18:33
@BlackHatSamurai..Ccould you tell me please how much 2147483647 (2^31 - 1) characters size can be in MB or GB ? – kelly Dec 07 '16 at 18:33
@PeterLawrey that is a good point. I'll update my answer. Thank you :) – BlackHatSamurai Dec 07 '16 at 18:35
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@kelly well it's simple math problem. 1 character = 1 byte. There are 1024 kb in a MB, and 1024 MB in GB... So do the math :) – BlackHatSamurai Dec 07 '16 at 18:40
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@BlackHatSamurai except in Java 8, 1 char uses 2 bytes of memory. In Java 9 one char might use 1 to 3 bytes. – Peter Lawrey Dec 07 '16 at 18:44
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@PeterLawrey Great information! Thanks. I wonder why they are using so much more memory for characters. I guess I'll have to look into it :D – BlackHatSamurai Dec 07 '16 at 19:53
@BlackHatSamurai to build a String you need something like a StringBuilder so to build a String from 1 MB you need 4 MB of memory of which 2 MB can be discarded. – Peter Lawrey Dec 07 '16 at 19:57
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@PeterLawrey that makes sense. Thanks for the info! – BlackHatSamurai Dec 07 '16 at 20:00

how much size java string variable can hold

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