org.github.jamm

Enum MemoryMeter.Guess

java.lang.Object

java.lang.Enum<MemoryMeter.Guess>

org.github.jamm.MemoryMeter.Guess

All Implemented Interfaces:

Serializable, Comparable<MemoryMeter.Guess>

Enclosing class:

MemoryMeter

public static enum MemoryMeter.Guess
extends Enum<MemoryMeter.Guess>

The different strategies that can be used by a MemoryMeter instance to measure the shallow size of an object.

Enum Constant Summary

Enum Constants

Enum Constant and Description
INSTRUMENTATION Relies on java.lang.instrument.Instrumentation to measure shallow object size.
INSTRUMENTATION_AND_SPECIFICATION Relies on java.lang.instrument.Instrumentation to measure non array object and the Specification approach to measure arrays.
SPECIFICATION Computes the shallow size of objects using VM information.
UNSAFE Relies on Unsafe to measure shallow object size.

Method Summary

Modifier and Type	Method and Description
boolean	canBeUsedAsFallbackFrom(MemoryMeter.Guess guess)
static void	checkOrder(List<MemoryMeter.Guess> guesses)
boolean	requireInstrumentation() Checks if this strategy requires Instrumentation to be present.
boolean	requireUnsafe() Checks if this strategy requires Unsafe to be present.
static MemoryMeter.Guess	valueOf(String name) Returns the enum constant of this type with the specified name.
static MemoryMeter.Guess[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

INSTRUMENTATION

public static final MemoryMeter.Guess INSTRUMENTATION

Relies on java.lang.instrument.Instrumentation to measure shallow object size. It requires Instrumentation to be available, but it is the most accurate strategy.

INSTRUMENTATION_AND_SPECIFICATION

public static final MemoryMeter.Guess INSTRUMENTATION_AND_SPECIFICATION

Relies on java.lang.instrument.Instrumentation to measure non array object and the Specification approach to measure arrays. This strategy tries to combine the best of both strategies the accuracy and speed of Instrumentation for non array object and the speed of Specification for measuring array objects for which all strategy are accurate. For some reason Instrumentation is slower for arrays before Java 17.

UNSAFE

public static final MemoryMeter.Guess UNSAFE

Relies on Unsafe to measure shallow object size. It requires Unsafe to be available. After INSTRUMENTATION based strategy UNSAFE is the most accurate strategy.

SPECIFICATION

public static final MemoryMeter.Guess SPECIFICATION

Computes the shallow size of objects using VM information.

Method Detail

values

public static MemoryMeter.Guess[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (MemoryMeter.Guess c : MemoryMeter.Guess.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static MemoryMeter.Guess valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

requireInstrumentation

public boolean requireInstrumentation()

Checks if this strategy requires Instrumentation to be present.

Returns:

true if this strategy requires Instrumentation to be present, false otherwise.

requireUnsafe

public boolean requireUnsafe()

Checks if this strategy requires Unsafe to be present.

Returns:

true if this strategy requires Unsafe to be present, false otherwise.

canBeUsedAsFallbackFrom

public boolean canBeUsedAsFallbackFrom(MemoryMeter.Guess guess)

checkOrder

public static void checkOrder(List<MemoryMeter.Guess> guesses)