Essentials

Essentials are a collection of general-purpose classes we found useful in many occasions.

• Write less code in your projects
• Specialized implementations for better performance compared to standard APIs
• Super light weight: < 100k in size
• Compatible with Android and Java

This project is bare bones compared to a rich menu offered by Guava or Apache Commons. Essentials is not a framework, it's rather a small set of utilities to make Java standard approaches more convenient or more efficient.

Website

JavaDoc (3.0 release candidate)

Changelog

Features

• IO utilities help with streams (byte and character based) and digests (e.g. MD5 and SHA-1).
• File utilities simplify reading and writing strings/bytes/objects from or to files. Also includes getting hashes from files and copying files.
• String utilities allow efficient splitting and joining of strings, hex and MD5 creation, and other useful string helpers.
• Date utilities.
• Better hash functions: our Murmur3 implementation provides superior hash quality and outperforms standard Java hash functions
• Specialized Streams: for example an optimized PipedOutputStream replacement (based on a circular byte buffer)
• Hash set and map for primitive long keys outperform the generic versions of the Java Collection APIs
• Multimaps provide a map of lists or sets to simplify storing multiple values for a single key
• Object cache with powerful configuration options: soft/weak/strong references, maximum size, and time-based expiration
• Base64 implementation (bundled from iharder.net) for lower versions of Java & Android (includes input/output streams)

Read more on our website.

Add the dependency to your project

You may also try the 3.0 release candidate with additional features and a cleaned up API:

compile 'org.greenrobot:essentials:3.0.0-RC1' 

Or, grab the older version:

compile 'de.greenrobot:java-common:2.3.1' 

And for Maven:

<dependency>
  <groupId>de.greenrobot</groupId>
  <artifactId>java-common</artifactId>
  <version>2.3.1</version> </dependency> 

Code samples (V2.3.1)

Example code on how to use some of the utility classes:

// Get all bytes from stream and close the stream safely byte[] bytes = IoUtils.readAllBytesAndClose(inputStream);
  // Read the contents of an file as a string (use readBytes to get byte[]) String contents = FileUtils.readUtf8(file);
  // How many days until new year's eve? long time2 = DateUtils.getTimeForDay(2015, 12, 31);
 int daysToNewYear = DateUtils.getDayDifference(time, time2);

Multimaps (added in V2.2):

ListMap<String,String> multimap = new ListMap<>();
 multimap.putElement("a", "1");
 multimap.putElement("a", "2");
 multimap.putElement("a", "3");
 List<String> strings = multimap.get("a");
 // Contains "1", "2", and "3"

Our hash functions implement java.util.zip.Checksum, so this code might look familiar to you:

Murmur3A murmur = new Murmur3A();
 murmur.update(bytes);
 long hash = murmur.getValue();

All hashes can be calculated progressively by calling update(...) multiple times. Our Murmur3A implementation goes a step further by offering updates with primitive data in a very efficient way:

// reuse the previous instance and start over to calculate a new hash murmur.reset();
  murmur.updateLong(42L);
  // Varargs and arrays are supported natively, too   murmur.updateInt(2014, 2015, 2016);
  murmur.updateUtf8("And strings, of course");
  // Hash for the previous update calls. No conversion to byte[] necessary. hash = murmur.getValue();

The utility classes are straight forward and don't have dependencies, so you should be fine to grasp them by having a look at their source code. Most of the method names should be self-explaining, and often you'll find JavaDocs where needed.

Build setup

Currently, Maven is used to build greenrobot-common. Inside of build-common, there are two parent POMs defined that might be useful: parent-pom and parent-pom-with-checks. The latter integrates FindBugs and Checkstyle in your build. Use it like this:

<parent>
  <groupId>de.greenrobot</groupId>
  <artifactId>parent-pom-with-checks</artifactId>
  <version>2.0.0</version>
  <relativePath></relativePath> </parent> 

License

Copyright (C) 2012-2016 Markus Junginger, greenrobot ( http://greenrobot.org)

EventBus binaries and source code can be used according to the Apache License, Version 2.0.

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