Above all, avoid falsehood, every kind of falsehood, especially falseness to yourself. Watch over your own deceitfulness and look into it every hour, every minute - Fyodor Dostoyevsky

Fyodor User Guide - String Generators

Fyodor has a simple default random string generator, running RDG.string().next(); right now returns 

2LWKjDK1o6}@ps9P>!^`B/VEq@4}B7

on my machine. You can of course customise this behaviour quite a lot.

String Length

The length of the string that a generator will return can be set, either as a fixed value or a Range:

RDG.string(Integer)
RDG.string(Range<Integer>)

So the default string generator is actually calling RDG.string(30) under the hood. Running RDG.string(Range.closed(10, 20)); just now on my machine returned

 >^ywmBa2Nl=
 8e{mZj]lq!!![TF
 q=F]}}S]|YZ
 jELPHnNm3pq<}uj@lZ
 ~\;$9^$g5Fi
 q}O<:8W>p!Y_Q9x/.
 16SID?/C=xs^//k
 YLvVdL0f{ddQ_1k:]hS`
 ndwhEp-//K
 Q~;x[aMjWZ
 0J!4l&y#]0+qO70
 bLI/,g<TtY=eTv\<fj
 f~(nd'(\/045,v0U4['
 ,5(iWyKr+(7{7u[0
 ^OH(1mUYy3oe4lR
 )K@0)M<C*)mNDzQ>\'
 PwGb\z{#MQ
 </*9!kJ_F!CS)$5FxQ!
 h-i{F[M(VQBe>K/{,,#
 WI+ldG6T{9nD%0[;KHy;

lovely.

Character Sets

You can also customise the set of characters that a StringGenerator will select from. There are several ways to do this, the simplest is probably this:

RDG.string(Integer, String)
RDG.string(Integer, char[])
RDG.string(Range<Integer>, String)
RDG.string(Range<Integer>, char[])

which will return a StringGenerator that takes the supplied chars as the underlying source. For instance in Fyodor's NINumberGenerator the last character needs to be an A, B, C or D. This is generated with 

RDG.string(1, "ABCD")

If this is too limited you can specify a range of integers that correspond to Unicode character points. The default set of characters in Fyodor (used in the examples above) is Range.closed(33,126) which corresponds to the following characters:

!#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

this is basically (almost - see later) the ASCII standard character set. You can create a StringGenerator with a different underlying character set by supplying one or more ranges as a parameter in addition to the length of the string to generate:

RDG.string(Integer lengthOfString, Range<Integer>... charSetRange)
RDG.string(Integer lengthOfString, CharacterSetRange... charSetRange)
RDG.string(Range<Integer> lengthOfString, Range<Integer>... charSetRange)
RDG.string(Range<Integer> lengthOfString, CharacterSetRange... charSetRange)

The CharacterSetRange in the code above is an enum with some pre-defined chunks of Unicode:

CharacterSetRange.defaultLatinBasic
CharacterSetRange.latin1
CharacterSetRange.latinExtendedA
CharacterSetRange.latinExtendedB

defaultLatinBasic

The default character set used (shown earlier) if none specified, this is the ASCII standard without the control characters (1 - 32, things like backspace, linefeed etc.) and without the double quote character (see later)

latin1

The non-control characters from the second Unicode block (160 - 255) - common international punctuation marks and accented or novel Latin characters for Western European languages:

 ¡¢£¤¥¦§¨©ª«¬­®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ

(the first character here is a non-breaking space)

latinExtendedA

The characters from the third Unicode block (256 - 383) - accented Latin characters for mostly eastern European languages:

ĀāĂ㥹ĆćĈĉĊċČčĎďĐđĒēĔĕĖėĘęĚěĜĝĞğĠġĢģĤĥĦħĨĩĪīĬĭĮįİıIJijĴĵĶķĸĹĺĻļĽľĿŀŁłŃńŅņŇňʼnŊŋŌōŎŏŐőŒœŔŕŖŗŘřŚśŜŝŞşŠšŢţŤťŦŧŨũŪūŬŭŮůŰűŲųŴŵŶŷŸŹźŻżŽžſ

latinExtendedB

The characters from the fourth Unicode block (384 - 591) - a whole mish-mash of weird and wonderful glyphs and characters from around the world:

ƀƁƂƃƄƅƆƇƈƉƊƋƌƍƎƏƐƑƒƓƔƕƖƗƘƙƚƛƜƝƞƟƠơƢƣƤƥƦƧƨƩƪƫƬƭƮƯưƱƲƳƴƵƶƷƸƹƺƻƼƽƾƿǀǁǂǃDŽDždžLJLjljNJNjnjǍǎǏǐǑǒǓǔǕǖǗǘǙǚǛǜǝǞǟǠǡǢǣǤǥǦǧǨǩǪǫǬǭǮǯǰDZDzdzǴǵǶǷǸǹǺǻǼǽǾǿȀȁȂȃȄȅȆȇȈȉȊȋȌȍȎȏȐȑȒȓȔȕȖȗȘșȚțȜȝȞȟȠȡȢȣȤȥȦȧȨȩȪȫȬȭȮȯȰȱȲȳȴȵȶȷȸȹȺȻȼȽȾȿɀɁɂɃɄɅɆɇɈɉɊɋɌɍɎɏ

As mentioned earlier you can supply more than one Range or CharacterSetRange when creating a StringGenerator if you have particularly exotic needs, the generator will choose characters from all of them.

Character Filters

A StringGenerator can also be created with a CharacterFilter. This is an interface used to fine-tune the underlying array of characters that a StringGenerator can select from:

public interface CharacterFilter {
    public boolean includeCharacter(char c);
}

This is called before each character from the Range is added to the StringGenerator's underlying character set. This is how the double-quotes are removed from the character set in the default StringGenerator implementation, or you can supply your own filter when you create a StringGenerator with the default character set:

RDG.string(Integer lengthOfString, CharacterFilter filter)
RDG.string(Range<Integer> lengthOfString, CharacterFilter filter)
RDG.string(Integer lengthOfString, CharacterSetFilter filter)
RDG.string(Range<Integer> lengthOfString, CharacterSetFilter filter)

The CharacterSetFilter in the code above is an enum with some pre-defined CharacterFilters:

CharacterSetFilter.AllExceptDoubleQuotes
CharacterSetFilter.DomainName
CharacterSetFilter.EmailLocalPart
CharacterSetFilter.LettersAndDigits
CharacterSetFilter.LettersOnly

AllExceptDoubleQuotes

Returns true for everything except double quotes, this is the default filter used if no other is specified.

LettersAndDigits

Only returns true if 

java.lang.Character.isLetterOrDigit(c)
returns true.

LettersOnly

Only returns true if 

java.lang.Character.isLetter(c)
returns true.

DomainName

Only returns true for letters, numbers or hyphens.

EmailLocalPart

Only returns true for the characters allowed in the local part (the bit before the '@') of an email address.

There is one more implementation of CharacterFilter available, which is RegExCharacterFilter which takes a regular expression string in its constructor. As the name suggests, this filters out any character that doesn't return true when matching the given regular expression. This is how the DomainName and EmailLocalPart filters are implemented.

You can of course combine a CharacterFilter with one or more Ranges when creating a StringGenerator:

RDG.string(Integer lengthOfString, CharacterSetFilter filter, Range<Integer>... charSetRanges)
RDG.string(Range<Integer> lengthOfString, CharacterSetFilter filter, Range<Integer>... charSetRanges)
RDG.string(Integer lengthOfString, CharacterFilter filter, Range<Integer>... charSetRanges)
RDG.string(Range<Integer> lengthOfString, CharacterFilter filter, Range<Integer>... charSetRanges)

Note: You can call char[] getCharSet() on any StringGenerator if it's easier to just fine tune the underlying charset of an existing generator (this returns a copy of the array used by the generator so you can add and remove characters without borking anything but it means you'll need to create a new generator to use it).

Next Page: Other Generators