javax.realtime

Class SizeEstimator

java.lang.Object

javax.realtime.SizeEstimator

public final class SizeEstimator
extends java.lang.Object

This class maintains an estimate of the amount of memory required to store a set of objects.

SizeEstimator is a floor on the amount of memory that should be allocated. Many objects allocate other objects when they are constructed. SizeEstimator only estimates the memory requirement of the object itself, it does not include memory required for any objects allocated at construction time. When the instance itself is allocated in several parts (when for instance the object and its monitor are separate), the size estimate shall include the sum of the sizes of all the parts that are allocated from the same memory area as the instance.

Alignment considerations, and possibly other order-dependent issues may cause the allocator to leave a small amount of unusable space, consequently the size estimate cannot be seen as more than a close estimate.

See Also:

MemoryArea(SizeEstimator)

Constructor Summary

Constructors

Constructor and Description
SizeEstimator() Create an empty size estimator.

Method Summary

Modifier and Type	Method and Description
void	clear() Restores the estimate value to zero for reuse.
long	getEstimate() Gets an estimate of the number of bytes needed to store all the objects reserved.
void	reserve(java.lang.Class<?> c, int number) Takes into account additional number instances of Class c when estimating the size of the MemoryArea.
void	reserve(SizeEstimator size) Takes into account an additional estimation from the instance of SizeEstimator size when estimating the size of the MemoryArea.
void	reserve(SizeEstimator estimator, int number) Takes into account additional number of the estimations from instances of SizeEstimator size when estimating the size of the MemoryArea.
void	reserveArray(int length) Takes into account an additional instance of an array of length reference values when estimating the size of the MemoryArea.
void	reserveArray(int length, java.lang.Class<?> type) Takes into account an additional instance of an array of length primitive values when estimating the size of the MemoryArea.
void	reserveLambda() Determines the size of a lambda with no closure and add it to this size estimator.
void	reserveLambda(EnclosedType first) Determines the size of a lambda with one variable in its closure and add it to this size estimator.
void	reserveLambda(EnclosedType first, EnclosedType second) Determines the size of a lambda with two variables in its closure and add it to this size estimator.
void	reserveLambda(EnclosedType first, EnclosedType second, EnclosedType... others) Determines the size of a lambda with more than two variables in its closure and add it to this size estimator.

Methods inherited from class java.lang.Object

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

Constructor Detail

SizeEstimator

public SizeEstimator()

Create an empty size estimator.

Method Detail

reserve

public void reserve(java.lang.Class<?> c,
                    int number)

Takes into account additional number instances of Class c when estimating the size of the MemoryArea.

Parameters:

c - The class to take into account.

number - The number of instances of c to estimate.

Throws:

StaticIllegalArgumentException - when c is null or number is negative.

Since:

RTSJ 2.0 throws StaticIllegalArgumentException also when number is less than zero.

reserve

public void reserve(SizeEstimator estimator,
                    int number)

Takes into account additional number of the estimations from instances of SizeEstimator size when estimating the size of the MemoryArea.

Parameters:

estimator - The given instance of SizeEstimator.

number - The number of times to reserve the size denoted by estimator.

Throws:

StaticIllegalArgumentException - when estimator is null or number is less than zero.

Since:

RTSJ 2.0 throws StaticIllegalArgumentException also when number is less than zero.

reserve

public void reserve(SizeEstimator size)

Takes into account an additional estimation from the instance of SizeEstimator size when estimating the size of the MemoryArea.

Parameters:

size - The given instance of SizeEstimator.

Throws:

StaticIllegalArgumentException - when size is null.

reserveArray

public void reserveArray(int length)

Takes into account an additional instance of an array of length reference values when estimating the size of the MemoryArea.

Parameters:

length - The number of entries in the array.

Throws:

StaticIllegalArgumentException - when length is negative.

Since:

RTSJ 1.0.1

reserveArray

public void reserveArray(int length,
                         java.lang.Class<?> type)

Takes into account an additional instance of an array of length primitive values when estimating the size of the MemoryArea.

Class values for the primitive types are available from the corresponding class types; e.g., Byte.TYPE, Integer.TYPE, and Short.TYPE.

Parameters:

length - The number of entries in the array.

type - The class representing a primitive type. The reservation will leave room for an array of length of the primitive type corresponding to type.

Throws:

StaticIllegalArgumentException - when length is negative, or type does not represent a primitive type.

Since:

RTSJ 1.0.1

reserveLambda

public void reserveLambda(EnclosedType first,
                          EnclosedType second,
                          EnclosedType... others)

Determines the size of a lambda with more than two variables in its closure and add it to this size estimator.

Parameters:

first - Type of first variable in closure.

second - Type of second variable in closure.

others - Types of additional variables in closure.

Since:

RTSJ 2.0

reserveLambda

public void reserveLambda(EnclosedType first,
                          EnclosedType second)

Determines the size of a lambda with two variables in its closure and add it to this size estimator.

Parameters:

first - Type of first variable in closure.

second - Type of second variable in closure.

Since:

RTSJ 2.0

reserveLambda

public void reserveLambda(EnclosedType first)

Determines the size of a lambda with one variable in its closure and add it to this size estimator.

Parameters:

first - Type of first variable in closure.

Since:

RTSJ 2.0

reserveLambda

public void reserveLambda()

Determines the size of a lambda with no closure and add it to this size estimator.

Since:

RTSJ 2.0

getEstimate

public long getEstimate()

Gets an estimate of the number of bytes needed to store all the objects reserved.

Returns:

the estimated size in bytes.

clear

public void clear()

Restores the estimate value to zero for reuse.

Since:

rtsj 2.0