How much memory is allocated to the String object in Java

	Size in bytes
String() object
Object header	16
Hash field	4
Reference to char array	4
Char[] array
Object header	16
Array length	4
Array size	N*2

String allocates in memory at least (24+20+N*2) bytes, where N - number of characters in the string. If N=10 then string size = 64 bytes.

One million of these strings = 64 000 000 bytes. But also we need array or collection to store these strings.
This requires additional memory.
ArrayList<String>(1 000 000) ~= 4 000 000 bytes (4 bytes per reference to string object).

So, total size will be 68 000 000 bytes.

Gist code: Output:

3,355,792 Initial
1,217,624 After GC
218,921,768 Created list of strings
76,489,936 After GC
68,000,000 Expected size in memory

But if you have many similar strings, then using of String.intern() greatly reduces amount of allocated memory. Output:

3,355,792 Initial
1,217,792 After GC
106,750,232 Created list of strings
13,127,480 After GC
68,000,000 Expected size in memory

10x less memory! 6.8 megabytes instead of 68

Convert image to base64

It is extremely simple, and  without server-side:

<script>
    function convertToBase64(event) {
        var file = event.target.files[0];
        var reader = new FileReader();
        reader.onload = function (event) {
            document.getElementById('text').value = event.target.result;
            document.getElementById('text').select();
        };
        reader.readAsDataURL(file);
    }
</script>

<input id="file" type="file" onchange="convertToBase64(event)">
<textarea id="text"> </textarea>

You may use it at: ImageToBase64 or directly from here:


See this project on GitHub

Xameleon

Just released web-camflash application Xameleon
Have Fun at Xameleon :-)

HTML Encoder

I've released new online service: HTML Encoder
It replaces ampersands, tabs, less/greater braces and prepares source code for posting into blog.

If you prefer shell scripts, you may use this:

sed -e 's/\x26/\&/g;s/\x3c/\</g;s/\x3e/\>/g' sourcefile.txt | expand -t 4 >sourcefile.blog

See this project on GitHub