ClassSize (Apache HBase 1.2.12 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

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`	`BYTE_BUFFER` Overhead for ByteBuffer
`static int`	`CELL_SKIPLIST_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
`private static org.apache.commons.logging.Log`	`LOG`
`static int`	`MAP_ENTRY` Overhead for entry in map
`private static int`	`nrOfRefsPerObj`
`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`	`STRING` String overhead
`static int`	`TIMERANGE` Overhead for timerange
`static int`	`TIMERANGE_TRACKER` Overhead for TimeRangeTracker
`static int`	`TREEMAP` Overhead for TreeMap

Constructor Summary

Constructors
Constructor and Description

ClassSize()

Constructors
Constructor and Description
`ClassSize()`

Method Summary

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 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.

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.apache.commons.logging.Log LOG
```
  - nrOfRefsPerObj
```
private static int nrOfRefsPerObj
```
  - ARRAY
```
public static final int ARRAY
```
    Array overhead
  - ARRAYLIST
```
public static final int ARRAYLIST
```
    Overhead for ArrayList(0)
  - 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
  - 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
  - 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
  - TIMERANGE_TRACKER
```
public static final int TIMERANGE_TRACKER
```
    Overhead for TimeRangeTracker
  - CELL_SKIPLIST_SET
```
public static final int CELL_SKIPLIST_SET
```
    Overhead for CellSkipListSet
- Constructor Detail
  - ClassSize
```
public ClassSize()
```
- Method Detail
  - 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.

Class ClassSize

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG

nrOfRefsPerObj

ARRAY

ARRAYLIST

BYTE_BUFFER

INTEGER

MAP_ENTRY

OBJECT

REFERENCE

STRING

TREEMAP

CONCURRENT_HASHMAP

CONCURRENT_HASHMAP_ENTRY

CONCURRENT_HASHMAP_SEGMENT

CONCURRENT_SKIPLISTMAP

CONCURRENT_SKIPLISTMAP_ENTRY

REENTRANT_LOCK

ATOMIC_LONG

ATOMIC_INTEGER

ATOMIC_BOOLEAN

COPYONWRITE_ARRAYSET

COPYONWRITE_ARRAYLIST

TIMERANGE

TIMERANGE_TRACKER

CELL_SKIPLIST_SET

Constructor Detail

ClassSize

Method Detail

getSizeCoefficients

estimateBaseFromCoefficients

estimateBase

align

align

is32BitJVM