![]() When there is a lack of ‘entropy’ in the operating system then random number generation will slow down. What does ‘entropy’ mean? Linux kernel uses certain techniques like user’s mouse movements, variance in the hardware fan noise, variance in the noise of the device drivers … to generate random numbers. #randomUUID() API internally uses ‘ en tropy‘ in the operating system to generate a unique number. Let’s discuss this API in this post with a real-world example. Under certain circumstances, using this API can affect your application’s availability. In that case, JUG in the time-based mode is a good choice.Java developers tend to use ‘#randomUUID()’ API, to generate a UUID (Universally Unique Identifier) number (i.e., ‘b8bbcbed-ca07-490c-8711-5118ee0af2f9’). If security is of ultimate importance to you, it cannot be used. If you need speed and/or support for EJBs or CORBA, UUID is the best way. Security aspects must be considered when version 1 UUIDs that contain the MAC address are made public. My own version does this without native code (tested on Windows, Linux, MacOSX, BSDs, Solaris, HP-UX) and falls back to random data if the MAC address cannot be read. Because there is no official way in Java to do this, JUG comes with a native library (compiled for Windows x86, FreeBSD, Linux x86, MacOSX PPC, SPARC). The computer’s MAC address must be encoded into a version 1 UUID. It might not be possible to use some implementations in environments like EJB containers. Some of the implementations are slower than others. The goodĪll of the implementations I tested generated unique UUIDs, even when used multi-threaded. ![]() With a modern computer, it is possible to generate more than 500.000 UUIDs per second. My own implementation is the fastest by a factor of at least two. The following table contains the timings in milliseconds for the creation of one million UUIDs with the various implementations. The following Java Virtual Machines were used:Īll Java Virtual Machines were started with -Xms256M -Xmx256M to force a fixed VM size. ![]() Load on the computer was low during the tests. The test computer was an Intel Pentium M 1.73 GHz computer with 1.5 GB of RAM. The performance of all generators was compared. ++: very good, +: good, o: acceptable, -: bad, -: very bad Usually, this is done from, although JUG also supports parsing from byte arrays. Parse: Whether parsing UUIDs is supported.CORBA: Whether the generated UUIDs can be used in CORBA.EJB: Whether the generated UUIDs can be used as primary keys in enterprise java beans.Speed: The performance of generating UUIDs.Versions: The UUID versions supported (1–5).Ease of use: How many lines of code does it take to get a UUID?.Commons Id – there is no release as of now.I did not compare the following packages: Generally, whenever unique values across different machines are needed, UUIDs are a good choice. Primary keys, replacing database sequences.Unique identifiers for website visitors.In this entry, I will compare three generators of UUIDs written in the Java programming language. UUIDs (or GUIDs) are unique identifiers that are frequently used in programming.
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