Package com.github.toolarium.common.util

Class RandomGenerator

java.lang.Object
com.github.toolarium.common.util.RandomGenerator
public final class RandomGenerator extends Object
This class implements some helper methods for random numbers. It works internal with the SecureRandom class.

  • Field Details

    • validNumberCharacters

      public static final char[] validNumberCharacters
      Defines valid number characters

    • validLowerCaseLetterCharacters

      public static final char[] validLowerCaseLetterCharacters
      Defines valid lower case letter characters

    • validUpperCaseLetterCharacters

      public static final char[] validUpperCaseLetterCharacters
      Defines valid upper case letter characters

    • validLetterCharacters

      public static final char[] validLetterCharacters
      Defines valid letter characters

    • validNumberLetterCharacters

      public static final char[] validNumberLetterCharacters
      Defines valid number and letter characters

    • ONE_DAY

      public static final long ONE_DAY
      The miliseconds of a day
      See Also:

  • Method Details

    • getInstance

      public static RandomGenerator getInstance()
      Get the instance
      Returns:
      the instance

    • getInstance

      public static RandomGenerator getInstance(SecureRandom random)
      Gets a secure random instance
      Parameters:
      random - initialize the random generator with the given secure random instance.
      Returns:
      the instance

    • getSecureRandom

      public SecureRandom getSecureRandom()
      Returns the secure random instance
      Returns:
      secure random instance

    • getBooleanRandom

      public Boolean getBooleanRandom()
      Returns a random number as a Boolean
      Returns:
      random Boolean

    • getIntegerRandom

      public Integer getIntegerRandom()
      Returns a random number as a Integer
      Returns:
      random Integer

    • getLongRandom

      public Long getLongRandom()
      Returns a random number as a Long
      Returns:
      random Long

    • getFloatRandom

      public Float getFloatRandom()
      Returns a random number as a Float
      Returns:
      random Float

    • getDoubleRandom

      public Double getDoubleRandom()
      Returns a random number as a Double
      Returns:
      random Double

    • getRandomByteArray

      public ByteArray getRandomByteArray(int size)
      Returns a random byte array
      Parameters:
      size - the size of the byte array
      Returns:
      random byte array

    • getRandomString

      public String getRandomString(int size)
      Returns a random string
      Parameters:
      size - the size of the string
      Returns:
      random string

    • getRandomString

      public String getRandomString(int size, char[] validCharacters)
      Returns a random string
      Parameters:
      size - the size of the string
      validCharacters - the valid characters for the random string
      Returns:
      random string

    • nextBytes

      public byte[] nextBytes(int size)
      Gets random bytes
      Parameters:
      size - the size of the random bytes
      Returns:
      the instance

    • createGUID

      public String createGUID()
      Generates a GUID: GUIDs are guaranteed to be globally unique by using ethernet MACs, IP addresses, time elements, and sequential numbers. GUIDs are not expected to be random and most often are easy/possible to guess given a sample from a given generator. GUIDs can be used as security devices to hide things such as files within a filesystem where listings are unavailable (e.g. files that are served up from a Web server with indexing turned off). This may be desireable in cases where standard authentication is not appropriate. In this scenario, the RandomGUIDs are used as directories. Another example is the use of GUIDs for primary keys in a database where you want to ensure that the keys are secret. Random GUIDs can then be used in a URL to prevent hackers (or users) from accessing records by guessing or simply by incrementing sequential numbers. There are many other possiblities of using GUIDs in the realm of security and encryption where the element of randomness is important. This method was written for these purposes but can also be used as a general purpose GUID generator as well. It generates truly random GUIDs by using the system's IP address (name/IP), system time in milliseconds (as an integer), and a very large random number joined together in a single String that is passed through an MD5 hash. The IP address and system time make the MD5 seed globally unique and the random number guarantees that the generated GUIDs will have no discernable pattern and cannot be guessed given any number of previously generated GUIDs. It is generally not possible to access the seed information (IP, time, random number) from the resulting GUIDs as the MD5 hash algorithm provides one way encryption.
      Returns:
      a unique GUID

    • createUUID

      public String createUUID()
      Creates a UUID
      Returns:
      the uuid

    • getRandomDayInFuture

      public Date getRandomDayInFuture(int dayRange)
      Get a date in the future
      Parameters:
      dayRange - the range of days
      Returns:
      the date

    • getRandomDateInFuture

      public Date getRandomDateInFuture(long milisecondRange)
      Get a date in the future
      Parameters:
      milisecondRange - the range in miliseconds
      Returns:
      the date

    • getRandomDayInPast

      public Date getRandomDayInPast(int dayRange)
      Get a date in the future
      Parameters:
      dayRange - the range of days
      Returns:
      the date

    • getRandomDateInPast

      public Date getRandomDateInPast(long milisecondRange)
      Get a date in the future
      Parameters:
      milisecondRange - the range in miliseconds
      Returns:
      the date

    • getRandomNumber

      public long getRandomNumber(long range, boolean allowZero)
      Gets a random long number
      Parameters:
      range - the range of the long. As example the range 5 means a random number between 1 and 5.
      allowZero - true if zero should also included into the range. As example the range 5 means a random number between 0 and 4.
      Returns:
      the random number

    • chisQuare

      public float chisQuare(int number, int size)
      Method to test the randomness of the random algorithm.
      Parameters:
      number - numbers of positiv numbers
      size - the numbers are less the size
      Returns:
      the chis-quare. If chis-quare is in the range from 2*sqr(size) to size, then the algorithm has a good randomness in case the number is 10*size.

    • combineValidCharacters

      public static char[] combineValidCharacters(char[] input, char[] input2)
      Helper methods to combines two character arrays
      Parameters:
      input - the input
      input2 - the input two
      Returns:
      the combined arrays