How to create an array of 20 random bytes

Question

How can I create an array of 20 random bytes in Java

User · Accepted Answer

Try the Random nextBytes method   byte   b   new byte 20   new Random   nextBytes b

User · Answer

If you are already using Apache Commons Lang  the  RandomUtils  makes this a one-liner  byte   randomBytes   RandomUtils nextBytes 20    Note  this does not produce cryptographically-secure bytes

User · Answer

Java 7 introduced ThreadLocalRandom which is isolated to the current thread   This is an another rendition of maerics s solution   final byte   bytes   new byte 20   ThreadLocalRandom current   nextBytes bytes

User · Answer

Create a Random object with a seed and get the array random by doing   public static final int ARRAY LENGTH   20   byte   byteArray   new byte ARRAY LENGTH   new Random System currentTimeMillis    nextBytes byteArray      get fisrt element System out println  Random byte      byteArray 0

User · Answer

For those wanting a more secure way to create a random byte array  yes the most secure way is   byte   bytes   new byte 20   SecureRandom getInstanceStrong   nextBytes bytes     BUT your threads might block if there is not enough randomness available on the machine  depending on your OS  The following solution will not block   SecureRandom random   new SecureRandom    byte   bytes   new byte 20   random nextBytes bytes     This is because the first example uses  dev random and will block while waiting for more randomness  generated by a mouse keyboard and other sources   The second example uses  dev urandom which will not block

User · Answer

If you want a cryptographically strong random number generator  also thread safe  without using a third party API  you can use SecureRandom   Java 6  amp  7   SecureRandom random   new SecureRandom    byte   bytes   new byte 20   random nextBytes bytes     Java 8  even more secure    byte   bytes   new byte 20   SecureRandom getInstanceStrong   nextBytes bytes

[java] How to create an array of 20 random bytes?

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