org.github.jamm

Class MemoryMeter

java.lang.Object

org.github.jamm.MemoryMeter

public final class MemoryMeter
extends Object

Utility to measure the heap space used by java objects.

This class supports multithreading and can be reused safely.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MemoryMeter.Builder Builder for MemoryMeter instances
static class	MemoryMeter.ByteBufferMode The different way of measuring deeply a ByteBuffer.
static class	MemoryMeter.Guess The different strategies that can be used by a MemoryMeter instance to measure the shallow size of an object.

Field Summary

Fields

Modifier and Type	Field and Description
static List<MemoryMeter.Guess>	BEST The default guesses in accuracy order.

Constructor Summary

Constructors

Constructor and Description
MemoryMeter(MemoryMeterStrategy strategy, FieldAndClassFilter classFilter, FieldFilter fieldFilter, MemoryMeterListener.Factory listenerFactory) Create a new MemoryMeter instance from the different component it needs to measure object graph.

Method Summary

Modifier and Type	Method and Description
static void	agentmain(String options, Instrumentation inst)
static MemoryMeter.Builder	builder()
static MemoryLayoutSpecification	getMemoryLayoutSpecification() Provides information about the memory layout used by the JVM.
static boolean	hasInstrumentation()
static boolean	hasUnsafe()
long	measure(Object object) Measures the shallow memory usage of the object.
long	measureArray(boolean[] array) Measures the shallow memory usage of the specified boolean array.
long	measureArray(byte[] array) Measures the shallow memory usage of the specified byte array.
long	measureArray(char[] array) Measures the shallow memory usage of the specified char array.
long	measureArray(double[] array) Measures the shallow memory usage of the specified double array.
long	measureArray(float[] array) Measures the shallow memory usage of the specified float array.
long	measureArray(int[] array) Measures the shallow memory usage of the specified int array.
long	measureArray(long[] array) Measures the shallow memory usage of the specified long array.
long	measureArray(Object[] array) Measures the shallow memory usage of the specified Object array.
long	measureArray(short[] array) Measures the shallow memory usage of the specified short array.
long	measureDeep(Object object) Measures the memory usage of the object including referenced objects.
long	measureDeep(Object object, MemoryMeter.ByteBufferMode bbMode) Measures the memory usage of the object including referenced objects.
long	measureStringDeep(String s) Measures the deep memory usage of the specified String
static void	premain(String options, Instrumentation inst)
static boolean	useStringOptimization()

Methods inherited from class java.lang.Object

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

Field Detail

BEST

public static final List<MemoryMeter.Guess> BEST

The default guesses in accuracy order.

Constructor Detail

MemoryMeter

public MemoryMeter(MemoryMeterStrategy strategy,
                   FieldAndClassFilter classFilter,
                   FieldFilter fieldFilter,
                   MemoryMeterListener.Factory listenerFactory)

Create a new MemoryMeter instance from the different component it needs to measure object graph.

Unless there is a specific need to override some of the MemoryMeter logic people should only create MemoryMeter instances through MemoryMeter.builder(). This constructor provides a way to modify part of the logic being used by allowing to use specific implementations for the strategy or filters.

Parameters:

strategy - the MemoryMeterStrategy to use for measuring object shallow size.

classFilter - the filter used to filter out classes from the measured object graph

fieldFilter - the filter used to filter out fields from the measured object graph

listenerFactory - the factory used to create the listener listening to the object graph traversal

Method Detail

premain

public static void premain(String options,
                           Instrumentation inst)

agentmain

public static void agentmain(String options,
                             Instrumentation inst)

hasInstrumentation

public static boolean hasInstrumentation()

hasUnsafe

public static boolean hasUnsafe()

useStringOptimization

public static boolean useStringOptimization()

builder

public static MemoryMeter.Builder builder()

getMemoryLayoutSpecification

public static MemoryLayoutSpecification getMemoryLayoutSpecification()

Provides information about the memory layout used by the JVM.

Returns:

information about the memory layout used by the JVM

measure

public long measure(Object object)

Measures the shallow memory usage of the object.

If the object is null the value returned will be zero.

Parameters:

object - the object to measure

Returns:

the shallow memory usage of @param object

measureArray

public long measureArray(Object[] array)

Measures the shallow memory usage of the specified Object array.

If the object is null the value returned will be zero.

Parameters:

array - the object array to measure

Returns:

the shallow memory usage of the array

measureArray

public long measureArray(byte[] array)

Measures the shallow memory usage of the specified byte array.

If the object is null the value returned will be zero.

Parameters:

array - the byte array to measure

Returns:

the shallow memory usage of the byte array

measureArray

public long measureArray(boolean[] array)

Measures the shallow memory usage of the specified boolean array.

If the object is null the value returned will be zero.

Parameters:

array - the boolean array to measure

Returns:

the shallow memory usage of the boolean array

measureArray

public long measureArray(short[] array)

Measures the shallow memory usage of the specified short array.

If the object is null the value returned will be zero.

Parameters:

array - the short array to measure

Returns:

the shallow memory usage of the short array

measureArray

public long measureArray(char[] array)

Measures the shallow memory usage of the specified char array.

If the object is null the value returned will be zero.

Parameters:

array - the char array to measure

Returns:

the shallow memory usage of the char array

measureArray

public long measureArray(int[] array)

Measures the shallow memory usage of the specified int array.

If the object is null the value returned will be zero.

Parameters:

array - the int array to measure

Returns:

the shallow memory usage of the int array

measureArray

public long measureArray(float[] array)

Measures the shallow memory usage of the specified float array.

If the object is null the value returned will be zero.

Parameters:

array - the float array to measure

Returns:

the shallow memory usage of the float array

measureArray

public long measureArray(double[] array)

Measures the shallow memory usage of the specified double array.

If the object is null the value returned will be zero.

Parameters:

array - the double array to measure

Returns:

the shallow memory usage of the double array

measureArray

public long measureArray(long[] array)

Measures the shallow memory usage of the specified long array.

If the object is null the value returned will be zero.

Parameters:

array - the long array to measure

Returns:

the shallow memory usage of the long array

measureStringDeep

public long measureStringDeep(String s)

Measures the deep memory usage of the specified String

Parameters:

s - the String to measure

Returns:

the deep memory usage of the specified string

measureDeep

public long measureDeep(Object object)

Measures the memory usage of the object including referenced objects.

If the object is null the value returned will be zero.

Calling this method is equivalent to calling measureDeep(object, ByteBufferMode) with a NORMAL ByteBufferMode.

Parameters:

object - the object to measure

Returns:

the memory usage of @param object including referenced objects

measureDeep

public long measureDeep(Object object,
                        MemoryMeter.ByteBufferMode bbMode)

Measures the memory usage of the object including referenced objects.

If the object is null the value returned will be zero.

Parameters:

object - the object to measure

bbMode - the mode that should be used to measure ByteBuffers.

Returns:

the memory usage of @param object including referenced objects