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org.apache.derby.iapi.services.cache
Class ClassSize  

java.lang.Object
  org.apache.derby.iapi.services.cache.ClassSize

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public class ClassSize

extends java.lang.Object

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Field Summary
private static int	booleanSize
private static java.util.Hashtable	catalog
private static int	charSize
private static int	doubleSize
private static boolean	dummyCatalog
private static int	floatSize
private static int	intSize
private static int	longSize
private static int	minObjectSize
(package private) static boolean	noGuess
private static int	objectOverhead
static int	refSize
private static int	shortSize
(package private) static boolean	unitTest
private static int[]	wildGuess

 

Constructor Summary

ClassSize()

 

Method Summary
static int	estimateAndCatalogBase(java.lang.Class cls)           Estimate the static space taken up by a class instance.
static int	estimateArrayOverhead()
static int	estimateBase(java.lang.Class cl)           Estimate the static space taken up by the fields of a class.
static int	estimateBaseFromCatalog(java.lang.Class cls)           Estimate the static space taken up by a class instance from cataloged coefficients.
private static int	estimateBaseFromCatalog(java.lang.Class cls, boolean addToCatalog)
static int	estimateBaseFromCoefficients(int[] coeff)           Estimate the static space taken up by a class instance given the coefficients returned by getSizeCoefficients.
static int	estimateHashEntrySize()           Estimate the size of a Hashtable entry.
static int	estimateMemoryUsage(java.lang.String str)           Estimate the size of a string.
static int	getIntSize()
static int	getRefSize()           Get the estimate of the size of an object reference.
static int[]	getSizeCoefficients(java.lang.Class cl)           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 void	setDummyCatalog()           do not try to use the catalog.

 

Methods inherited from class java.lang.Object

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

 

Field Detail

refSize

public static final int refSize

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objectOverhead

private static final int objectOverhead

See Also:

Constant Field Values

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booleanSize

private static final int booleanSize

See Also:

Constant Field Values

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charSize

private static final int charSize

See Also:

Constant Field Values

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shortSize

private static final int shortSize

See Also:

Constant Field Values

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intSize

private static final int intSize

See Also:

Constant Field Values

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longSize

private static final int longSize

See Also:

Constant Field Values

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floatSize

private static final int floatSize

See Also:

Constant Field Values

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doubleSize

private static final int doubleSize

See Also:

Constant Field Values

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minObjectSize

private static final int minObjectSize

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dummyCatalog

private static boolean dummyCatalog

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noGuess

static boolean noGuess

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unitTest

static boolean unitTest

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wildGuess

private static final int[] wildGuess

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catalog

private static java.util.Hashtable catalog

Constructor Detail

ClassSize

public ClassSize()

Method Detail

setDummyCatalog

public static void setDummyCatalog()

do not try to use the catalog.

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getRefSize

public static int getRefSize()

Get the estimate of the size of an object reference.

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getIntSize

public static int getIntSize()

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getSizeCoefficients

public static int[] getSizeCoefficients(java.lang.Class cl)

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.

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estimateBaseFromCoefficients

public static int estimateBaseFromCoefficients(int[] coeff)

Estimate the static space taken up by a class instance given the coefficients returned by getSizeCoefficients.

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estimateBaseFromCatalog

public static int estimateBaseFromCatalog(java.lang.Class cls)

Estimate the static space taken up by a class instance from cataloged coefficients.

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estimateBaseFromCatalog

private static int estimateBaseFromCatalog(java.lang.Class cls,
                                           boolean addToCatalog)

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estimateAndCatalogBase

public static int estimateAndCatalogBase(java.lang.Class cls)

Estimate the static space taken up by a class instance. Save the coefficients in a catalog.

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estimateBase

public static int estimateBase(java.lang.Class cl)

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.

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estimateArrayOverhead

public static int estimateArrayOverhead()

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estimateHashEntrySize

public static int estimateHashEntrySize()

Estimate the size of a Hashtable entry. In Java 1.2 we can use Map.entry, but this is not available in earlier versions of Java.

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estimateMemoryUsage

public static int estimateMemoryUsage(java.lang.String str)

Estimate the size of a string.

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> apache >> derby >> iapi >> services >> [ cache overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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