SimpleHashSet

Simple HashSet. Save 25% memory for you.

License	Apache 2
GroupId	in.srain.cube
ArtifactId	simple-hashset
Last Version	1.0.1
Release Date	Jan 12, 2015
Type	jar
Description	SimpleHashSet Simple HashSet. Save 25% memory for you.
Source Code Management	https://github.com/liaohuqiu/SimpleHashSet

Download simple-hashset

Filename	Size
simple-hashset-1.0.1.pom
simple-hashset-1.0.1.jar	8 KB
simple-hashset-1.0.1-sources.jar	3 KB
simple-hashset-1.0.1-javadoc.jar	45 KB

How to add to project

Apache Maven

<!-- https://jarcasting.com/artifacts/in.srain.cube/simple-hashset/ -->
<dependency>
    <groupId>in.srain.cube</groupId>
    <artifactId>simple-hashset</artifactId>
    <version>1.0.1</version>
</dependency>

Gradle Groovy

// https://jarcasting.com/artifacts/in.srain.cube/simple-hashset/
implementation 'in.srain.cube:simple-hashset:1.0.1'

Gradle Kotlin

// https://jarcasting.com/artifacts/in.srain.cube/simple-hashset/
implementation ("in.srain.cube:simple-hashset:1.0.1")

Apache Buildr

'in.srain.cube:simple-hashset:jar:1.0.1'

Apache Ivy

<dependency org="in.srain.cube" name="simple-hashset" rev="1.0.1">
  <artifact name="simple-hashset" type="jar" />
</dependency>

Groovy Grape

@Grapes(
@Grab(group='in.srain.cube', module='simple-hashset', version='1.0.1')
)

Scala SBT

libraryDependencies += "in.srain.cube" % "simple-hashset" % "1.0.1"

Leiningen

[in.srain.cube/simple-hashset "1.0.1"]

Dependencies

test (1)

Group / Artifact	Type	Version
junit : junit	jar	3.8.1

Project Modules

There are no modules declared in this project.

中文说明

maven Central

<dependency>
    <groupId>in.srain.cube</groupId>
    <artifactId>simple-hashset</artifactId>
    <type>jar</type>
    <version>1.0.1</version>
</dependency>

gradle:

compile 'in.srain.cube:simple-hashset:1.0.1'

Save 25% memory

Object Size in Java: http://www.codeinstructions.com/2008/12/java-objects-memory-structure.html, http://btoddb-java-sizing.blogspot.com/2012/01/object-sizes.html

Object Size in Davlik : http://www.liaohuqiu.net/posts/android-object-size-dalvik/

In fact, java.util.HashSet is just a wrapper of java.util.HashMap, so its retained heap size is O(n * entry_size).

The java.util.HashMap is using separate chaining to process collision, n is the sum of the count of element and the count of free slots remain in array.

The entry_size is the shadow heap size of the jave.util.HashMap.Entry.

The definition of java.util.HashMap.Entry:

static class Entry<K,V> implements Map.Entry<K,V> {
    final K key;
    V value;
    Entry<K,V> next;
    int hash;
}

So the shadow heap size is:

• 32bit JVM: 8 + 4 * 4 = 24 bytes
• 64bit JVM -UseCompressedOops: 16 + 8 * 4 = 48 bytes.
• 64bit JVM +UseCompressedOops: 12 + 4 * 4 + 4(padding) = 32 bytes.
• Davlik: 12 + 4 * 4 + 4(padding) = 32 bytes.

In fact V value is usless for HashSet, we can implement a HashSet use the following SimpleHashSetEntry:

private static class SimpleHashSetEntry<T> {

    private int mHash;
    private T mKey;
    private SimpleHashSetEntry<T> mNext;
}

The retained heap size is:

• 32bit JVM: 8 + 4 * 3 + (padding) = 24 bytes
• 64bit JVM -UseCompressedOops: 16 + 8 * 3 = 40 bytes. (8 bytes saved, 16.66%)
• 64bit JVM +UseCompressedOops: 12 + 4 * 3 = 24 bytes. (8 bytes saved, 25%)
• Davlik: 12 + 4 * 3 = 24 bytes (8 bytes saved, 25%).

License

Apache 2

Versions

Version
1.0.1 Jan 12, 2015