Package com.github.toolarium.common.util

Class RandomGenerator

  • public final class RandomGenerator
extends java.lang.Object
    This class implements some helper methods for random numbers. It works internal with the SecureRandom class.

    • Field Detail

      • 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

    • Method Detail

      • getInstance

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

      • getInstance

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

      • getSecureRandom

        public java.security.SecureRandom getSecureRandom()
        Returns the secure random instance
        Returns:
        secure random instance

      • getBooleanRandom

        public java.lang.Boolean getBooleanRandom()
        Returns a random number as a Boolean
        Returns:
        random Boolean

      • getIntegerRandom

        public java.lang.Integer getIntegerRandom()
        Returns a random number as a Integer
        Returns:
        random Integer

      • getLongRandom

        public java.lang.Long getLongRandom()
        Returns a random number as a Long
        Returns:
        random Long

      • getFloatRandom

        public java.lang.Float getFloatRandom()
        Returns a random number as a Float
        Returns:
        random Float

      • getDoubleRandom

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

      • getRandomString

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

      • getRandomDayInFuture

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

      • getRandomDateInFuture

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

      • getRandomDayInPast

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

      • getRandomDateInPast

        public java.util.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