org.h2.util
Class MemoryUtils

java.lang.Object
  org.h2.util.MemoryUtils

public class MemoryUtils
extends java.lang.Object

This is a utility class with functions to measure the free and used memory.

Field Summary

static byte[]	EMPTY_BYTES An 0-size byte array.
static int[]	EMPTY_INT_ARRAY An 0-size int array.
static long[]	EMPTY_LONG_ARRAY An 0-size long array.

Method Summary

static void	allocateReserveMemory() Allocate a little main memory that is freed up when if no memory is available, so that rolling back a large transaction is easier.
static boolean	freeReserveMemory() Free up the reserve memory.
static int	getMemoryFree() Get the free memory in KB.
static int	getMemoryUsed() Get the used memory in KB.
static byte[]	newBytes(int len) Create an array of bytes with the given size.
static int[]	newIntArray(int len) Create an int array with the given size.
static long[]	newLongArray(int len) Create a long array with the given size.

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY_BYTES

public static final byte[] EMPTY_BYTES

An 0-size byte array.

EMPTY_INT_ARRAY

public static final int[] EMPTY_INT_ARRAY

An 0-size int array.

EMPTY_LONG_ARRAY

public static final long[] EMPTY_LONG_ARRAY

An 0-size long array.

Method Detail

getMemoryUsed

public static int getMemoryUsed()

Get the used memory in KB.

Returns:

the used memory

getMemoryFree

public static int getMemoryFree()

Get the free memory in KB.

Returns:

the used memory

allocateReserveMemory

public static void allocateReserveMemory()

Allocate a little main memory that is freed up when if no memory is available, so that rolling back a large transaction is easier.

freeReserveMemory

public static boolean freeReserveMemory()

Free up the reserve memory.

Returns:

if memory could be freed up.

newBytes

public static byte[] newBytes(int len)

Create an array of bytes with the given size. If this is not possible because not enough memory is available, an OutOfMemoryError with the requested size in the message is thrown.

Parameters:

len - the number of bytes requested

Returns:

the byte array

Throws:

java.lang.OutOfMemoryError

newIntArray

public static int[] newIntArray(int len)

Create an int array with the given size.

Parameters:

len - the number of bytes requested

Returns:

the int array

newLongArray

public static long[] newLongArray(int len)

Create a long array with the given size.

Parameters:

len - the number of bytes requested

Returns:

the int array