Secure Random Generation in Java 8

Java has been under fire for several years for having security holes. Justified or not, a lot of work has been done to fortify the JVM and frameworks from possible attacks. Random numbers with a low-level of entropy make systems that use random number generators to create encryption keys or hash sensitive information more susceptible to hacking.

So far selection of the Random Number Generation algorithms has been left to the developer. The problem is that where implementations depend on specific hardware / OS / JVM, the desired algorithm may not be available. In such cases applications have a tendency to default to weaker generators, which can put them at greater risk of attack.

Java 8 has added a new method called SecureRandom.getInstanceStrong() whose aim is to have the JVM choose a secure provider for you. If you’re writing code without complete control of the OS / hardware / JVM on which it would run (which is very common when deploying to the cloud or PaaS), my suggestion is to give this approach some serious consideration.
See more here: http://www.infoq.com/articles/Java-8-Quiet-Features

Java Random thread save

Examples:

ThreadLocalRandom.current().nextInt()
ThreadLocalRandom.current().nextDouble()
...

Random number in java 7

Since java 7 you should use ThreadLocalRandom.current().nextInt() over Math.random() for generating random numbers. ThreadLocalRandom use random seed per thread, so threads do not compete for it.