Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.iapi.services.cache.ClassSize

Modifier and Type	Field and Description
private static final int	booleanSize
private static final int	charSize
private static final int	doubleSize
private static boolean	dummyCatalog
private static final int	floatSize
private static final int	intSize
private static final int	longSize
private static final int	minObjectSize
pack-priv static boolean	noGuess
private static final int	objectOverhead
public static final int	refSize
private static final int	shortSize
pack-priv static boolean	unitTest
private static final int[]	wildGuess

Access	Constructor and Description
public	ClassSize()

Method Summary

Modifier and Type	Method and Description
public static int	Returns: the size estimate, in bytes estimateAndCatalogBase(Class<T> the class cls) Estimate the static space taken up by a class instance.
public static int	Returns: the estimated overhead of an array. The estimated size of an x[n] array is estimateArrayOverhead() + n*sizeOf(x). estimateArrayOverhead()
public static int	Returns: the size estimate in bytes. estimateBase(Class<T> A class cl) Estimate the static space taken up by the fields of a class.
public static int	Returns: the size estimate, in bytes estimateBaseFromCatalog(Class<T> the class cls) Estimate the static space taken up by a class instance from cataloged coefficients.
private static int	estimateBaseFromCatalog(Class<?> cls, boolean addToCatalog)
public static int	Returns: the size estimate, in bytes estimateBaseFromCoefficients(int[] the coefficients coeff) Estimate the static space taken up by a class instance given the coefficients returned by getSizeCoefficients.
public static int	Returns: the estimate, in bytes estimateHashEntrySize() Estimate the size of a Hashtable entry.
public static int	Returns: the estimated size, in bytes estimateMemoryUsage(String The string str) Estimate the size of a string.
private static final int	Returns: The reference size in bytes as specified or implied by the VM, or `-1` if the reference size couldn't be determined. fetchRefSizeFromSystemProperties() Tries to determine the reference size in bytes by checking whether the VM we're running in is 32 or 64 bit by looking at the system properties.
public static int	Returns: the estimate of the size of a primitive int getIntSize()
public static int	Returns: the estimate in bytes. getRefSize() Get the estimate of the size of an object reference.
public static int[]	Returns: an array of 2 integers. The first integer is the constant part of the function, the second is the reference size coefficient. getSizeCoefficients(Class<T> A class whose instance size is to be estimated 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.
private static final String	Returns: The property value, or `null` if it doesn't exist or the required permission to read the property is missing. getSystemProperty(final String name of the system property to read propName) Attempts to read the specified system property.
private static void	runFinalization(Runtime runtime) This method exists merely to suppress the "removal" warning.
public static void	setDummyCatalog() do not try to use the catalog.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

booleanSize	back to summary
private static final int booleanSize

charSize	back to summary
private static final int charSize

doubleSize	back to summary
private static final int doubleSize

dummyCatalog	back to summary
private static boolean dummyCatalog

floatSize	back to summary
private static final int floatSize

intSize	back to summary
private static final int intSize

longSize	back to summary
private static final int longSize

minObjectSize	back to summary
private static final int minObjectSize

noGuess	back to summary
pack-priv static boolean noGuess

objectOverhead	back to summary
private static final int objectOverhead

refSize	back to summary
public static final int refSize

shortSize	back to summary
private static final int shortSize

unitTest	back to summary
pack-priv static boolean unitTest

wildGuess	back to summary
private static final int[] wildGuess

ClassSize	back to summary
public ClassSize()

Method Detail

estimateAndCatalogBase back to summary

estimateAndCatalogBase	back to summary
public static int estimateAndCatalogBase(Class<T> cls) Estimate the static space taken up by a class instance. Save the coefficients in a catalog. Parameters cls:Class<T> the class Returns:int the size estimate, in bytes See Also `estimateBaseFromCoefficients`, `see org.apache.derbyBuild.ClassSizeCrawler`

public static int estimateAndCatalogBase(Class<T> cls)

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

Parameters

cls:Class<T>: the class

Returns:int

the size estimate, in bytes

estimateArrayOverhead	back to summary
public static int estimateArrayOverhead() Returns:int the estimated overhead of an array. The estimated size of an x[n] array is estimateArrayOverhead() + n*sizeOf(x).

estimateBase back to summary

estimateBase	back to summary
public static int estimateBase(Class<T> 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. Parameters cl:Class<T> A class Returns:int the size estimate in bytes. See Also `estimateBaseFromCatalog`

public static int estimateBase(Class<T> 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.

Parameters

cl:Class<T>: A class

Returns:int

the size estimate in bytes.

See Also

estimateBaseFromCatalog

estimateBaseFromCatalog back to summary

estimateBaseFromCatalog	back to summary
public static int estimateBaseFromCatalog(Class<T> cls) Estimate the static space taken up by a class instance from cataloged coefficients. Parameters cls:Class<T> the class Returns:int the size estimate, in bytes See Also `estimateBaseFromCoefficients`, `see org.apache.derbyBuild.ClassSizeCrawler`

public static int estimateBaseFromCatalog(Class<T> cls)

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

Parameters

cls:Class<T>: the class

Returns:int

the size estimate, in bytes

estimateBaseFromCatalog	back to summary
private static int estimateBaseFromCatalog(Class<?> cls, boolean addToCatalog)

estimateBaseFromCoefficients	back to summary
public static int estimateBaseFromCoefficients(int[] coeff) Estimate the static space taken up by a class instance given the coefficients returned by getSizeCoefficients. Parameters coeff:int[] the coefficients Returns:int the size estimate, in bytes

estimateBaseFromCoefficients

back to summary

public static int estimateBaseFromCoefficients(int[] coeff)

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

Parameters

coeff:int[]: the coefficients

Returns:int

the size estimate, in bytes

estimateHashEntrySize	back to summary
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. Returns:int the estimate, in bytes

estimateHashEntrySize

back to summary

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.

Returns:int: the estimate, in bytes

estimateMemoryUsage	back to summary
public static int estimateMemoryUsage(String str) Estimate the size of a string. Parameters str:String The string Returns:int the estimated size, in bytes

estimateMemoryUsage

back to summary

public static int estimateMemoryUsage(String str)

Estimate the size of a string.

Parameters

str:String: The string

Returns:int

the estimated size, in bytes

fetchRefSizeFromSystemProperties back to summary

fetchRefSizeFromSystemProperties	back to summary
private static final int fetchRefSizeFromSystemProperties() Tries to determine the reference size in bytes by checking whether the VM we're running in is 32 or 64 bit by looking at the system properties. Returns:int The reference size in bytes as specified or implied by the VM, or `-1` if the reference size couldn't be determined.

private static final int fetchRefSizeFromSystemProperties()

Tries to determine the reference size in bytes by checking whether the VM we're running in is 32 or 64 bit by looking at the system properties.

Returns:int: The reference size in bytes as specified or implied by the VM, or -1 if the reference size couldn't be determined.

getIntSize	back to summary
public static int getIntSize() Returns:int the estimate of the size of a primitive int

getRefSize	back to summary
public static int getRefSize() Get the estimate of the size of an object reference. Returns:int the estimate in bytes.

getRefSize

back to summary

public static int getRefSize()

Get the estimate of the size of an object reference.

Returns:int: the estimate in bytes.

getSizeCoefficients	back to summary
public static int[] getSizeCoefficients(Class<T> 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. Parameters cl:Class<T> A class whose instance size is to be estimated Returns:int[] an array of 2 integers. The first integer is the constant part of the function, the second is the reference size coefficient.

getSizeCoefficients

back to summary

public static int[] getSizeCoefficients(Class<T> 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.

Parameters

cl:Class<T>: A class whose instance size is to be estimated

Returns:int[]

an array of 2 integers. The first integer is the constant part of the function, the second is the reference size coefficient.

getSystemProperty back to summary

getSystemProperty	back to summary
private static final String getSystemProperty(final String propName) Attempts to read the specified system property. Parameters propName:String name of the system property to read Returns:String The property value, or `null` if it doesn't exist or the required permission to read the property is missing.

private static final String getSystemProperty(final String propName)

Attempts to read the specified system property.

Parameters

propName:String: name of the system property to read

Returns:String

The property value, or null if it doesn't exist or the required permission to read the property is missing.

runFinalization	back to summary
private static void runFinalization(Runtime runtime) This method exists merely to suppress the "removal" warning. Annotations @SuppressWarnings:deprecation, removal

runFinalization

back to summary

private static void runFinalization(Runtime runtime)

This method exists merely to suppress the "removal" warning.

Annotations

@SuppressWarnings:deprecation, removal

setDummyCatalog	back to summary
public static void setDummyCatalog() do not try to use the catalog.

public Class ClassSize

Field Summary

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Field Detail

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Method Detail