ClassSize (Apache HBase 2.4.0 API)

java.lang.Object
- org.apache.hadoop.hbase.util.ClassSize

```
@InterfaceAudience.Private
public class ClassSize
extends Object
```
Class for determining the "size" of a class, an attempt to calculate the actual bytes that an object of this class will occupy in memory The core of this class is taken from the Derby project

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`private static class`	`ClassSize.MemoryLayout` MemoryLayout abstracts details about the JVM object layout.
`private static class`	`ClassSize.UnsafeLayout` UnsafeLayout uses Unsafe to guesstimate the object-layout related parameters like object header sizes and oop sizes See HBASE-15950.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`ARRAY` Array overhead
`static int`	`ARRAYLIST` Overhead for ArrayList(0)
`static int`	`ATOMIC_BOOLEAN` Overhead for AtomicBoolean
`static int`	`ATOMIC_INTEGER` Overhead for AtomicInteger
`static int`	`ATOMIC_LONG` Overhead for AtomicLong
`static int`	`ATOMIC_REFERENCE` Overhead for AtomicReference
`static int`	`BYTE_BUFFER` Overhead for ByteBuffer
`static int`	`CELL_ARRAY_MAP` Overhead for CellArrayMap
`static int`	`CELL_ARRAY_MAP_ENTRY` Overhead for Cell Array Entry
`static int`	`CELL_CHUNK_MAP` Overhead for CellChunkMap
`static int`	`CELL_CHUNK_MAP_ENTRY` Overhead for Cell Chunk Map Entry
`static int`	`CELL_FLAT_MAP` Overhead for CellFlatMap
`static int`	`CELL_SET` Overhead for CellSkipListSet
`static int`	`CONCURRENT_HASHMAP` Overhead for ConcurrentHashMap
`static int`	`CONCURRENT_HASHMAP_ENTRY` Overhead for ConcurrentHashMap.Entry
`static int`	`CONCURRENT_HASHMAP_SEGMENT` Overhead for ConcurrentHashMap.Segment
`static int`	`CONCURRENT_SKIPLISTMAP` Overhead for ConcurrentSkipListMap
`static int`	`CONCURRENT_SKIPLISTMAP_ENTRY` Overhead for ConcurrentSkipListMap Entry
`static int`	`COPYONWRITE_ARRAYLIST` Overhead for CopyOnWriteArrayList
`static int`	`COPYONWRITE_ARRAYSET` Overhead for CopyOnWriteArraySet
`static int`	`INTEGER` Overhead for an Integer
`static int`	`LINKEDLIST` Overhead for LinkedList(0)
`static int`	`LINKEDLIST_ENTRY` Overhead for a single entry in LinkedList
`private static org.slf4j.Logger`	`LOG`
`static int`	`MAP_ENTRY` Overhead for entry in map
`private static ClassSize.MemoryLayout`	`memoryLayout`
`static int`	`NON_SYNC_TIMERANGE_TRACKER` Overhead for NonSyncTimeRangeTracker
`static int`	`OBJECT` Object overhead is minimum 2 * reference size (8 bytes on 64-bit)
`static int`	`REENTRANT_LOCK` Overhead for ReentrantReadWriteLock
`static int`	`REFERENCE` Reference size is 8 bytes on 64-bit, 4 bytes on 32-bit
`static int`	`STORE_SERVICES`
`static int`	`STRING` String overhead
`static int`	`SYNC_TIMERANGE_TRACKER` Overhead for SyncTimeRangeTracker
`static int`	`TIMERANGE` Overhead for timerange
`static int`	`TREEMAP` Overhead for TreeMap
`private static boolean`	`USE_UNSAFE_LAYOUT`

Constructor Summary

Constructors
Constructor and Description

ClassSize()

Constructors
Constructor and Description
`ClassSize()`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static int`	`align(int num)` Aligns a number to 8.
`static long`	`align(long num)` Aligns a number to 8.
`static long`	`estimateBase(Class cl, boolean debug)` Estimate the static space taken up by the fields of a class.
`private static long`	`estimateBaseFromCoefficients(int[] coeff, boolean debug)` Estimate the static space taken up by a class instance given the coefficients returned by getSizeCoefficients.
`private static ClassSize.MemoryLayout`	`getMemoryLayout()`
`private static int[]`	`getSizeCoefficients(Class cl, boolean debug)` The estimate of the size of a class instance depends on whether the JVM uses 32 or 64 bit addresses, that is it depends on the size of an object reference.
`static boolean`	`is32BitJVM()` Determines if we are running in a 32-bit JVM.
`static long`	`sizeOf(byte[] b)` Calculate the memory consumption (in byte) of a byte array, including the array header and the whole backing byte array.
`static long`	`sizeOfByteArray(int len)` Calculate the memory consumption (in byte) of a part of a byte array, including the array header and the part of the backing byte array.
`static boolean`	`useUnsafeLayout()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LOG
```
private static final org.slf4j.Logger LOG
```
  - ARRAY
```
public static final int ARRAY
```
    Array overhead
  - ARRAYLIST
```
public static final int ARRAYLIST
```
    Overhead for ArrayList(0)
  - LINKEDLIST
```
public static final int LINKEDLIST
```
    Overhead for LinkedList(0)
  - LINKEDLIST_ENTRY
```
public static final int LINKEDLIST_ENTRY
```
    Overhead for a single entry in LinkedList
  - BYTE_BUFFER
```
public static final int BYTE_BUFFER
```
    Overhead for ByteBuffer
  - INTEGER
```
public static final int INTEGER
```
    Overhead for an Integer
  - MAP_ENTRY
```
public static final int MAP_ENTRY
```
    Overhead for entry in map
  - OBJECT
```
public static final int OBJECT
```
    Object overhead is minimum 2 * reference size (8 bytes on 64-bit)
  - REFERENCE
```
public static final int REFERENCE
```
    Reference size is 8 bytes on 64-bit, 4 bytes on 32-bit
  - STRING
```
public static final int STRING
```
    String overhead
  - TREEMAP
```
public static final int TREEMAP
```
    Overhead for TreeMap
  - CONCURRENT_HASHMAP
```
public static final int CONCURRENT_HASHMAP
```
    Overhead for ConcurrentHashMap
  - CONCURRENT_HASHMAP_ENTRY
```
public static final int CONCURRENT_HASHMAP_ENTRY
```
    Overhead for ConcurrentHashMap.Entry
  - CONCURRENT_HASHMAP_SEGMENT
```
public static final int CONCURRENT_HASHMAP_SEGMENT
```
    Overhead for ConcurrentHashMap.Segment
  - CONCURRENT_SKIPLISTMAP
```
public static final int CONCURRENT_SKIPLISTMAP
```
    Overhead for ConcurrentSkipListMap
  - CONCURRENT_SKIPLISTMAP_ENTRY
```
public static final int CONCURRENT_SKIPLISTMAP_ENTRY
```
    Overhead for ConcurrentSkipListMap Entry
  - CELL_FLAT_MAP
```
public static final int CELL_FLAT_MAP
```
    Overhead for CellFlatMap
  - CELL_CHUNK_MAP
```
public static final int CELL_CHUNK_MAP
```
    Overhead for CellChunkMap
  - CELL_CHUNK_MAP_ENTRY
```
public static final int CELL_CHUNK_MAP_ENTRY
```
    Overhead for Cell Chunk Map Entry
  - CELL_ARRAY_MAP
```
public static final int CELL_ARRAY_MAP
```
    Overhead for CellArrayMap
  - CELL_ARRAY_MAP_ENTRY
```
public static final int CELL_ARRAY_MAP_ENTRY
```
    Overhead for Cell Array Entry
  - REENTRANT_LOCK
```
public static final int REENTRANT_LOCK
```
    Overhead for ReentrantReadWriteLock
  - ATOMIC_LONG
```
public static final int ATOMIC_LONG
```
    Overhead for AtomicLong
  - ATOMIC_INTEGER
```
public static final int ATOMIC_INTEGER
```
    Overhead for AtomicInteger
  - ATOMIC_BOOLEAN
```
public static final int ATOMIC_BOOLEAN
```
    Overhead for AtomicBoolean
  - ATOMIC_REFERENCE
```
public static final int ATOMIC_REFERENCE
```
    Overhead for AtomicReference
  - COPYONWRITE_ARRAYSET
```
public static final int COPYONWRITE_ARRAYSET
```
    Overhead for CopyOnWriteArraySet
  - COPYONWRITE_ARRAYLIST
```
public static final int COPYONWRITE_ARRAYLIST
```
    Overhead for CopyOnWriteArrayList
  - TIMERANGE
```
public static final int TIMERANGE
```
    Overhead for timerange
  - SYNC_TIMERANGE_TRACKER
```
public static final int SYNC_TIMERANGE_TRACKER
```
    Overhead for SyncTimeRangeTracker
  - NON_SYNC_TIMERANGE_TRACKER
```
public static final int NON_SYNC_TIMERANGE_TRACKER
```
    Overhead for NonSyncTimeRangeTracker
  - CELL_SET
```
public static final int CELL_SET
```
    Overhead for CellSkipListSet
  - STORE_SERVICES
```
public static final int STORE_SERVICES
```
  - memoryLayout
```
private static final ClassSize.MemoryLayout memoryLayout
```
  - USE_UNSAFE_LAYOUT
```
private static final boolean USE_UNSAFE_LAYOUT
```
- Constructor Detail
  - ClassSize
```
public ClassSize()
```
- Method Detail
  - getMemoryLayout
```
private static ClassSize.MemoryLayout getMemoryLayout()
```
  - useUnsafeLayout
```
public static boolean useUnsafeLayout()
```
  - getSizeCoefficients
```
private static int[] getSizeCoefficients(Class cl,
                                         boolean debug)
```
    The estimate of the size of a class instance depends on whether the JVM uses 32 or 64 bit addresses, that is it depends on the size of an object reference. It is a linear function of the size of a reference, e.g. 24 + 5*r where r is the size of a reference (usually 4 or 8 bytes). This method returns the coefficients of the linear function, e.g. {24, 5} in the above example.
    
    Parameters:
    
    cl - A class whose instance size is to be estimated
    
    debug - debug flag
    
    Returns:
    
    an array of 3 integers. The first integer is the size of the primitives, the second the number of arrays and the third the number of references.
  - estimateBaseFromCoefficients
```
private static long estimateBaseFromCoefficients(int[] coeff,
                                                 boolean debug)
```
    Estimate the static space taken up by a class instance given the coefficients returned by getSizeCoefficients.
    
    Parameters:
    
    coeff - the coefficients
    
    debug - debug flag
    
    Returns:
    
    the size estimate, in bytes
  - estimateBase
```
public static long estimateBase(Class cl,
                                boolean debug)
```
    Estimate the static space taken up by the fields of a class. This includes the space taken up by by references (the pointer) but not by the referenced object. So the estimated size of an array field does not depend on the size of the array. Similarly the size of an object (reference) field does not depend on the object.
    
    Parameters:
    
    cl - class
    
    debug - debug flag
    
    Returns:
    
    the size estimate in bytes.
  - align
```
public static int align(int num)
```
    Aligns a number to 8.
    
    Parameters:
    
    num - number to align to 8
    
    Returns:
    
    smallest number >= input that is a multiple of 8
  - align
```
public static long align(long num)
```
    Aligns a number to 8.
    
    Parameters:
    
    num - number to align to 8
    
    Returns:
    
    smallest number >= input that is a multiple of 8
  - is32BitJVM
```
public static boolean is32BitJVM()
```
    Determines if we are running in a 32-bit JVM. Some unit tests need to know this too.
  - sizeOf
```
public static long sizeOf(byte[] b)
```
    Calculate the memory consumption (in byte) of a byte array, including the array header and the whole backing byte array. If the whole byte array is occupied (not shared with other objects), please use this function. If not, please use sizeOfByteArray(int) instead.
    
    Parameters:
    
    b - the byte array
    
    Returns:
    
    the memory consumption (in byte) of the whole byte array
  - sizeOfByteArray
```
public static long sizeOfByteArray(int len)
```
    Calculate the memory consumption (in byte) of a part of a byte array, including the array header and the part of the backing byte array. This function is used when the byte array backs multiple objects. For example, in KeyValue, multiple KeyValue objects share a same backing byte array (KeyValue.bytes). Also see KeyValue.heapSize().
    
    Parameters:
    
    len - the length (in byte) used partially in the backing byte array
    
    Returns:
    
    the memory consumption (in byte) of the part of the byte array

Class ClassSize

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG

ARRAY

ARRAYLIST

LINKEDLIST

LINKEDLIST_ENTRY

BYTE_BUFFER

INTEGER

MAP_ENTRY

OBJECT

REFERENCE

STRING

TREEMAP

CONCURRENT_HASHMAP

CONCURRENT_HASHMAP_ENTRY

CONCURRENT_HASHMAP_SEGMENT

CONCURRENT_SKIPLISTMAP

CONCURRENT_SKIPLISTMAP_ENTRY

CELL_FLAT_MAP

CELL_CHUNK_MAP

CELL_CHUNK_MAP_ENTRY

CELL_ARRAY_MAP

CELL_ARRAY_MAP_ENTRY

REENTRANT_LOCK

ATOMIC_LONG

ATOMIC_INTEGER

ATOMIC_BOOLEAN

ATOMIC_REFERENCE

COPYONWRITE_ARRAYSET

COPYONWRITE_ARRAYLIST

TIMERANGE

SYNC_TIMERANGE_TRACKER

NON_SYNC_TIMERANGE_TRACKER

CELL_SET

STORE_SERVICES

memoryLayout

USE_UNSAFE_LAYOUT

Constructor Detail

ClassSize

Method Detail

getMemoryLayout

useUnsafeLayout

getSizeCoefficients

estimateBaseFromCoefficients

estimateBase

align

align

is32BitJVM

sizeOf

sizeOfByteArray