de.uni_hildesheim.sse.monitoring.runtime.configuration

Class ObjectSizeCache

java.lang.Object

de.uni_hildesheim.sse.monitoring.runtime.configuration.ObjectSizeCache

public class ObjectSizeCache
extends java.lang.Object

Implements an object size cache, a simplified and typed version the hashmap java.util.HashMap.

Since:

1.00

Version:

1.00

Author:

from SUN/ORACLE

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	ObjectSizeCache.Entry Implements a bucket entry.

Field Summary

Fields

Modifier and Type	Field and Description
private static int	DEFAULT_INITIAL_CAPACITY The default initial capacity - MUST be a power of two.
private static float	DEFAULT_LOAD_FACTOR The load factor used when none specified in constructor.
static ObjectSizeCache	INSTANCE Stores the singleton instance of this class.
private float	loadFactor The load factor for the hash table.
private static int	MAXIMUM_CAPACITY The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments.
private static IObjectSizeProvider	objectSizeProvider Stores the object size provider.
private int	size The number of key-value mappings contained in this map.
private ObjectSizeCache.Entry[]	table The table, resized as necessary.
private int	threshold The next size value at which to resize (capacity * load factor).

Constructor Summary

Constructors

Modifier	Constructor and Description
private	ObjectSizeCache() Constructs an empty HashMap with the default initial capacity (16) and the default load factor (0.75).

Method Summary

Modifier and Type	Method and Description
(package private) void	addEntry(int hash, java.lang.Object key, long size, int bucketIndex) Adds a new entry with the specified key, value and hash code to the specified bucket.
void	clear() Removes all of the mappings from this map.
long	getClassSize(java.lang.String className) Returns the size of the class specified by className.
long	getSize(java.lang.Object object, boolean remember) Returns the memory size of object.
(package private) static int	hash(int key) Applies a supplemental hash function to a given hashCode, which defends against poor quality hash functions.
(package private) static int	indexFor(int hash, int length) Returns index for hash code h.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
void	remove(java.lang.Object key) Removes the mapping of key to its memory size.
(package private) void	resize(int newCapacity) Rehashes the contents of this map into a new array with a larger capacity.
void	setSize(java.lang.Object key, long size) Associates the specified value with the specified key in this map.
int	size() Returns the number of key-value mappings in this map.
(package private) void	transfer(ObjectSizeCache.Entry[] newTable) Transfers all entries from current table to newTable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INSTANCE

public static final ObjectSizeCache INSTANCE

Stores the singleton instance of this class.

objectSizeProvider

private static IObjectSizeProvider objectSizeProvider

Stores the object size provider.

DEFAULT_INITIAL_CAPACITY

private static final int DEFAULT_INITIAL_CAPACITY

The default initial capacity - MUST be a power of two.

See Also:

Constant Field Values

MAXIMUM_CAPACITY

private static final int MAXIMUM_CAPACITY

The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments. MUST be a power of two <= 1<<30.

See Also:

Constant Field Values

DEFAULT_LOAD_FACTOR

private static final float DEFAULT_LOAD_FACTOR

The load factor used when none specified in constructor.

See Also:

Constant Field Values

table

private transient ObjectSizeCache.Entry[] table

The table, resized as necessary. Length MUST Always be a power of two.

size

private transient int size

The number of key-value mappings contained in this map.

threshold

private int threshold

The next size value at which to resize (capacity * load factor).

loadFactor

private final float loadFactor

The load factor for the hash table.

Constructor Detail

ObjectSizeCache

private ObjectSizeCache()

Constructs an empty HashMap with the default initial capacity (16) and the default load factor (0.75).

Method Detail

hash

static int hash(int key)

Applies a supplemental hash function to a given hashCode, which defends against poor quality hash functions. This is critical because HashMap uses power-of-two length hash tables, that otherwise encounter collisions for hashCodes that do not differ in lower bits. Note: Null keys always map to hash 0, thus index 0.

Parameters:

key - the key to hash

Returns:

the hash value

indexFor

static int indexFor(int hash,
                    int length)

Returns index for hash code h.

Parameters:

hash - the hash code

length - the length of the table

Returns:

the index

setSize

public void setSize(java.lang.Object key,
                    long size)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.

Parameters:

key - the name of the class or the Class to associate the size to

size - the memory size to be associated with the className

addEntry

void addEntry(int hash,
              java.lang.Object key,
              long size,
              int bucketIndex)

Adds a new entry with the specified key, value and hash code to the specified bucket. It is the responsibility of this method to resize the table if appropriate. Subclass overrides this to alter the behavior of put method.

Parameters:

hash - the hash code

key - the class name of the class or the Class

size - the memory size of the class with className

bucketIndex - the target bucket index

resize

void resize(int newCapacity)

Rehashes the contents of this map into a new array with a larger capacity. This method is called automatically when the number of keys in this map reaches its threshold. If current capacity is MAXIMUM_CAPACITY, this method does not resize the map, but sets threshold to Integer.MAX_VALUE. This has the effect of preventing future calls.

Parameters:

newCapacity - the new capacity, MUST be a power of two; must be greater than current capacity unless current capacity is MAXIMUM_CAPACITY (in which case value is irrelevant).

transfer

void transfer(ObjectSizeCache.Entry[] newTable)

Transfers all entries from current table to newTable.

Parameters:

newTable - the target table

getClassSize

public long getClassSize(java.lang.String className)

Returns the size of the class specified by className. Please note that this method is intended to be used while instrumentation for improving the runtime performance of the memory size determination.

Parameters:

className - the name of the class

Returns:

the memory size of the class denoted by className, 0 if the class is not known to this cache.

Since:

1.00

getSize

public long getSize(java.lang.Object object,
                    boolean remember)

Returns the memory size of object. In case that the class of object is already known to this cache, the stored size is returned. Else the objectSizeProvider is used to determine the size.

Parameters:

object - the object to determine the size for

remember - if true remember an unknown size, false if an unknown size may be ignroed

Returns:

the memory size of object

remove

public void remove(java.lang.Object key)

Removes the mapping of key to its memory size.

Parameters:

key - the name of the class or the Class the mapping to the memory size shall be removed

Since:

1.00

size

public int size()

Returns the number of key-value mappings in this map.

Returns:

the number of key-value mappings in this map

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Returns:

true if this map contains no key-value mappings

clear

public void clear()

Removes all of the mappings from this map. The map will be empty after this call returns.