Admin: /* Memory usage and space in Java */

2018-01-07T09:07:39Z

Memory usage and space in Java

← Older revision		Revision as of 09:07, 7 January 2018
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			=Rules of Thumb=

	==Memory usage and space in Java==		==Memory usage and space in Java==

	Primitive ~~tyeps~~:		Primitive types:
	* boolean - 1 byte		* boolean - 1 byte
	* byte - 1 byte		* byte - 1 byte
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	* double[][] = 8n^2 + 32n + 24 ~ 8n^2		* double[][] = 8n^2 + 32n + 24 ~ 8n^2


			=Computing Max Memory=

			Max memory for a java application :

			<pre>
			[-Xmx] + [-XX:MaxPermSize] + number_of_threads * [-Xss]
			</pre>

			VM memory overhead is not a fixed %.


			=Flags=

	[[Category:Memory]]		[[Category:Memory]]
	[[Category:Java]]		[[Category:Java]]
	{{CSFlag}}		{{CSFlag}}

Admin: Created page with "==Memory usage and space in Java== Primitive tyeps: * boolean - 1 byte * byte - 1 byte * char - 2 bytes * int - 4 bytes * float - 4 bytes * long - 8 bytes * double - 8 bytes..."

2017-05-31T02:33:07Z

Created page with "==Memory usage and space in Java== Primitive tyeps: * boolean - 1 byte * byte - 1 byte * char - 2 bytes * int - 4 bytes * float - 4 bytes * long - 8 bytes * double - 8 bytes..."

New page

==Memory usage and space in Java==

Primitive tyeps:
* boolean - 1 byte
* byte - 1 byte
* char - 2 bytes
* int - 4 bytes
* float - 4 bytes
* long - 8 bytes
* double - 8 bytes

An integer has 2^32 different values, with 32 bits or 4 bytes (since there are 8 bits per byte)

Objects:
* Object overhead is 16 bytes of object overhead for each object
* References to objects typically use 8 bytes of memory.
* Data types can contain references to objects. The data type automatically incurs 16 bytes overhead for each object instance, plus 8 more bytes for each object's reference to another object.

Arrays:
* Arrays are implemented in Java as objects, with two instance variables - a pointer to the memory location of the first array element, and the length of the array.
* Primitive types - arrays use 24 bytes of header information, plus n times number of bytes to store each element

Example: int array
* int = 4 bytes
* int[] = 4n + 24 ~ 4n bytes

Example: double array 1D
* double = 8 bytes
* double[] = 8n + 24 ~ 8n bytes
* double[][] = 8n^2 + 32n + 24 ~ 8n^2

[[Category:Memory]]
[[Category:Java]]
{{CSFlag}}

Java/Memory - Revision history

Admin: /* Memory usage and space in Java */

Admin: Created page with "==Memory usage and space in Java== Primitive tyeps: * boolean - 1 byte * byte - 1 byte * char - 2 bytes * int - 4 bytes * float - 4 bytes * long - 8 bytes * double - 8 bytes..."