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noackjr and cgdecker Lazily allocate CompactHash backing arrays on first write
Empty maps/sets are extremely common. Lazily allocating the backing arrays can
save hundreds of KB of heap and reduce load on the garbage collector.

While here:
- Use serialized size to pre-size the arrays
- Respect ordering during serialization (without using an iterator)
- Consistently mark unused links as UNSET

Memory savings before first write (bytes):
- CompactHashMap.create(): 184 -> 64
- CompactLinkedHashMap.create(): 240 -> 80
- CompactHashSet.create(): 136 -> 40
- CompactLinkedHashSet.create(): 200 -> 56
- CompactHashMap.createWithExpectedSize(0): 136 -> 64
- CompactLinkedHashMap.createWithExpectedSize(0): 168 -> 80
- CompactHashSet.createWithExpectedSize(0): 96 -> 40
- CompactLinkedHashSet.createWithExpectedSize(0): 144 -> 56

RELNOTES=n/a

-------------
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Latest commit be92294 Mar 11, 2019
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README.md

Guava: Google Core Libraries for Java

Latest release Build Status

Guava is a set of core libraries that includes new collection types (such as multimap and multiset), immutable collections, a graph library, functional types, an in-memory cache, and APIs/utilities for concurrency, I/O, hashing, primitives, reflection, string processing, and much more!

Guava comes in two flavors.

  • The JRE flavor requires JDK 1.8 or higher.
  • If you need support for JDK 1.7 or Android, use the Android flavor. You can find the Android Guava source in the android directory.

Adding Guava to your build

Guava's Maven group ID is com.google.guava and its artifact ID is guava. Guava provides two different "flavors": one for use on a (Java 8+) JRE and one for use on Android or Java 7 or by any library that wants to be compatible with either of those. These flavors are specified in the Maven version field as either 27.1-jre or 27.1-android. For more about depending on Guava, see using Guava in your build.

To add a dependency on Guava using Maven, use the following:

<dependency>
  <groupId>com.google.guava</groupId>
  <artifactId>guava</artifactId>
  <version>27.1-jre</version>
  <!-- or, for Android: -->
  <version>27.1-android</version>
</dependency>

To add a dependency using Gradle:

dependencies {
  compile 'com.google.guava:guava:27.1-jre'
  // or, for Android:
  api 'com.google.guava:guava:27.1-android'
}

Snapshots

Snapshots of Guava built from the master branch are available through Maven using version HEAD-jre-SNAPSHOT, or HEAD-android-SNAPSHOT for the Android flavor.

  • Snapshot API Docs: guava
  • Snapshot API Diffs: guava

Learn about Guava

Links

IMPORTANT WARNINGS

  1. APIs marked with the @Beta annotation at the class or method level are subject to change. They can be modified in any way, or even removed, at any time. If your code is a library itself (i.e. it is used on the CLASSPATH of users outside your own control), you should not use beta APIs, unless you repackage them. If your code is a library, we strongly recommend using the Guava Beta Checker to ensure that you do not use any @Beta APIs!

  2. APIs without @Beta will remain binary-compatible for the indefinite future. (Previously, we sometimes removed such APIs after a deprecation period. The last release to remove non-@Beta APIs was Guava 21.0.) Even @Deprecated APIs will remain (again, unless they are @Beta). We have no plans to start removing things again, but officially, we're leaving our options open in case of surprises (like, say, a serious security problem).

  3. Guava has one dependency that is needed at runtime: com.google.guava:failureaccess:1.0

  4. Serialized forms of ALL objects are subject to change unless noted otherwise. Do not persist these and assume they can be read by a future version of the library.

  5. Our classes are not designed to protect against a malicious caller. You should not use them for communication between trusted and untrusted code.

  6. For the mainline flavor, we unit-test the libraries using only OpenJDK 1.8 on Linux. Some features, especially in com.google.common.io, may not work correctly in other environments. For the Android flavor, our unit tests run on API level 15 (Ice Cream Sandwich).

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