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Rarely available and hard-to-write Java utilities, written correctly, and thoroughly tested
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Rarely available and hard-to-write Java utilities, written correctly, and thoroughly tested (> 98% code coverage via JUnit tests).

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Including in java-util:

  • ArrayUtilities - Useful utilities for working with Java's arrays [ ]
  • ByteUtilities - Useful routines for converting byte[] to HEX character [] and visa-versa.
  • CaseInsensitiveMap - When Strings are used as keys, they are compared without case. Can be used as regular Map with any Java object as keys, just specially handles Strings.
  • CaseInsensitiveSet - Set implementation that ignores String case for contains() calls, yet can have any object added to it (does not limit you to adding only Strings to it).
  • Converter - Convert from once instance to another. For example, convert("45.3", BigDecimal.class) will convert the String to a BigDecimal. Works for all primitives, primitive wrappers, Date, java.sql.Date, String, BigDecimal, BigInteger, AtomicBoolean, AtomicLong, etc. The method is very generous on what it allows to be converted. For example, a Calendar instance can be input for a Date or Long. Examine source to see all possibilities.
  • DateUtilities - Robust date String parser that handles date/time, date, time, time/date, string name months or numeric months, skips comma, etc. English month names only (plus common month name abbreviations), time with/without seconds or milliseconds, y/m/d and m/d/y ordering as well.
  • DeepEquals - Compare two object graphs and return 'true' if they are equivalent, 'false' otherwise. This will handle cycles in the graph, and will call an equals() method on an object if it has one, otherwise it will do a field-by-field equivalency check for non-transient fields.
  • EncryptionUtilities - Makes it easy to compute MD5, SHA-1, SHA-256, SHA-512 checksums for Strings, byte[], as well as making it easy to AES-128 encrypt Strings and byte[]'s.
  • Executor - One line call to execute operating system commands. Executor executor = new Executor(); executor.exec('ls -l'); Call executor.getOut() to fetch the output, executor.getError() retrieve error output. If a -1 is returned, there was an error.
  • FastByteArrayOutputStream - Unlike the JDK ByteArrayOutputStream, FastByteArrayOutputStream is 1) not synchronized, and 2) allows access to it's internal byte[] eliminating the duplication of the byte[] when toByteArray() is called.
  • GraphComparator - Compare any two Java object graphs. It generates a List of Delta objects which describe the difference between the two Object graphs. This Delta list can be played back, such that List deltas =, target); GraphComparator.applyDelta(source, deltas) will bring source up to match target. See JUnit test cases for example usage. This is a completely thorough graph difference (and apply delta), including support for Array, Collection, Map, and object field differences.
  • IOUtilities - Handy methods for simplifying I/O including such niceties as properly setting up the input stream for HttpUrlConnections based on their specified encoding. Single line .close() method that handles exceptions for you.
  • MathUtilities - Handy mathematical algorithms to make your code smaller. For example, minimum of array of values.
  • ReflectionUtils - Simple one-liners for many common reflection tasks.
  • SafeSimpleDateFormat - Instances of this class can be stored as member variables and reused without any worry about thread safety. Fixing the problems with the JDK's SimpleDateFormat and thread safety (no reentrancy support).
  • StringUtilities - Helpful methods that make simple work of common String related tasks.
  • SystemUtilities - A Helpful utility methods for working with external entities like the OS, environment variables, and system properties.
  • TrackingMap - Map class that tracks when the keys are accessed via .get() or .containsKey(). Provided by @seankellner
  • Traverser - Pass any Java object to this Utility class, it will call your passed in anonymous method for each object it encounters while traversing the complete graph. It handles cycles within the graph. Permits you to perform generalized actions on all objects within an object graph.
  • UniqueIdGenerator - Generates a Java long unique id, that is unique across up to 100 servers in a cluster, never hands out the same value, has massive entropy, and runs very quickly.
  • UrlUtitilies - Fetch cookies from headers, getUrlConnections(), HTTP Response error handler, and more.
  • UrlInvocationHandler - Use to easily communicate with RESTful JSON servers, especially ones that implement a Java interface that you have access to.

See for revision history.

By: John DeRegnaucourt and Ken Partlow

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