H2 Database Engine 2.3.232 · org.h2.util.Utils · APIdia, the JavaDoc alternative

Modifier and Type	Class and Description
public static interface	Utils.ClassFactory The utility methods will try to use the provided class factories to convert binary name of class to Class object.

Modifier and Type	Field and Description
public static final byte[]	EMPTY_BYTES An 0-size byte array.
public static final int[]	EMPTY_INT_ARRAY An 0-size int array.
private static final HashMap<String, byte[]>	RESOURCES

Access	Constructor and Description
private	Utils()

Method Summary

Modifier and Type	Method and Description
public static Object	Returns: the return value from this call callMethod(Object the instance on which the call is done instance, String a string with the method name methodName, Object... the method parameters params) Calls an instance method via reflection.
private static Object	callMethod(Object instance, Class<?> clazz, String methodName, Object... params)
public static Object	Returns: the return value from this call callStaticMethod(String a string with the entire class and method name, eg. "java.lang.System.gc" classAndMethod, Object... the method parameters params) Calls a static method via reflection.
public static byte[]	Returns: a new byte array cloneByteArray(byte[] the byte array (may not be null) b) Create a new byte array and copy all the data.
public static synchronized void	collectGarbage() Run Java memory garbage collection.
public static boolean	Returns: true if both byte arrays contain the same bytes compareSecure(byte[] the first array test, byte[] the second array good) Compare two byte arrays.
public static byte[]	Returns: the target array or a new one if the target array was too small copy(byte[] the source array source, byte[] the target array target) Copy the contents of the source array to the target array.
public static byte[]	Returns: the byte array copyBytes(byte[] source array bytes, int the number of bytes in the new array len) Creates a copy of array of bytes with the new size.
public static ThreadPoolExecutor	createSingleThreadExecutor(String threadName)
public static ThreadPoolExecutor	createSingleThreadExecutor(String threadName, BlockingQueue<Runnable> workQueue)
public static long	Returns: time in nanoseconds, never equal to 0 currentNanoTime() Returns the current value of the high-resolution time source.
public static long	Returns: time in nanoseconds, never equal to 0 currentNanoTimePlusMillis(int additional offset in milliseconds ms) Returns the current value of the high-resolution time source plus the specified offset.
public static void	flushExecutor(ThreadPoolExecutor to flush executor) Makes sure that all currently submitted tasks are processed before this method returns.
public static int	Returns: the hash code getByteArrayHash(byte[] the byte array value) Calculate the hash code of the given byte array.
public static long	getGarbageCollectionCount()
public static long	getGarbageCollectionTime()
public static long	Returns: the free memory getMemoryFree() Get the free memory in KB.
public static long	Returns: the maximum memory getMemoryMax() Get the maximum memory in KB.
public static long	Returns: the used memory getMemoryUsed() Get the used memory in KB.
public static Class<?>	Returns: the non-primitive class (for example: java.lang.Integer) getNonPrimitiveClass(Class<?> the class (for example: int) clazz) Convert primitive class names to java.lang.* class names.
public static String	Returns: the value getProperty(String the key key, String the default value defaultValue) Get the system property.
public static int	Returns: the value getProperty(String the key key, int the default value defaultValue) Get the system property.
public static boolean	Returns: the value getProperty(String the key key, boolean the default value defaultValue) Get the system property.
public static byte[]	Returns: the resource data getResource(String the name of the resource name) Get a resource from the resource map.
public static int	Returns: the index indexOf(byte[] the byte array bytes, byte[] the pattern pattern, int the start index from where to search start) Calculate the index of the first occurrence of the pattern in the byte array, starting with the given index.
private static byte[]	loadResource(String name)
private static int	match(Class<?>[] params, Object[] values)
public static long	Returns: time in nanoseconds, never equal to 0 nanoTimePlusMillis(long time in nanoseconds nanoTime, int additional offset in milliseconds ms) Returns the current value of the high-resolution time source plus the specified offset.
public static byte[]	Returns: the byte array newBytes(int the number of bytes requested len) Create an array of bytes with the given size.
public static Object	Returns: the newly created object newInstance(String a string with the entire class, eg. "java.lang.Integer" className, Object... the constructor parameters params) Creates a new instance.
public static < the type T> ArrayList<T>	Returns: the object newSmallArrayList() Create a new ArrayList with an initial capacity of 4.
public static boolean	Returns: parsed or default value parseBoolean(String string to parse value, boolean value to return if value is null or on parsing error defaultValue, boolean throw exception on parsing error or return default value instead throwException) Parses the specified string to boolean value.
private static < the type of elements X> void	partialQuickSort(X[] the array to sort array, int the lower index with data, inclusive low, int the higher index with data, inclusive, `high > low` high, Comparator<? super X> the comparator comp, int the start index of requested region, inclusive start, int the end index of requested region, inclusive, `end >= start` end) Partial quick sort.
public static int	Returns: the scaled value scaleForAvailableMemory(int the value to scale value) Scale the value with the available memory.
public static void	shutdownExecutor(ThreadPoolExecutor executor)
public static < the type of elements X> void	sortTopN(X[] the array. array, int the start index, inclusive fromInclusive, int the end index, exclusive toExclusive, Comparator<? super X> the comparator. comp) Find the top limit values using given comparator and place them as in a full array sort, in descending order.

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

EMPTY_BYTES	back to summary
public static final byte[] EMPTY_BYTES An 0-size byte array.

EMPTY_INT_ARRAY	back to summary
public static final int[] EMPTY_INT_ARRAY An 0-size int array.

RESOURCES	back to summary
private static final HashMap<String, byte[]> RESOURCES

Utils	back to summary
private Utils()

Method Detail

callMethod	back to summary
public static Object callMethod(Object instance, String methodName, Object... params) throws Exception Calls an instance method via reflection. This will try to use the method where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases). Parameters instance:Object the instance on which the call is done methodName:String a string with the method name params:Object[] the method parameters Returns:Object the return value from this call Exceptions Exception: on failure

callMethod

back to summary

public static Object callMethod(Object instance, String methodName, Object... params) throws Exception

Calls an instance method via reflection. This will try to use the method where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases).

Parameters

instance:Object: the instance on which the call is done
methodName:String: a string with the method name
params:Object[]: the method parameters

Returns:Object

the return value from this call

Exceptions

Exception:: on failure

callMethod	back to summary
private static Object callMethod(Object instance, Class<?> clazz, String methodName, Object... params) throws Exception

callStaticMethod	back to summary
public static Object callStaticMethod(String classAndMethod, Object... params) throws Exception Calls a static method via reflection. This will try to use the method where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases). Parameters classAndMethod:String a string with the entire class and method name, eg. "java.lang.System.gc" params:Object[] the method parameters Returns:Object the return value from this call Exceptions Exception: on failure

callStaticMethod

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public static Object callStaticMethod(String classAndMethod, Object... params) throws Exception

Calls a static method via reflection. This will try to use the method where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases).

Parameters

classAndMethod:String: a string with the entire class and method name, eg. "java.lang.System.gc"
params:Object[]: the method parameters

Returns:Object

the return value from this call

Exceptions

Exception:: on failure

cloneByteArray	back to summary
public static byte[] cloneByteArray(byte[] b) Create a new byte array and copy all the data. If the size of the byte array is zero, the same array is returned. Parameters b:byte[] the byte array (may not be null) Returns:byte[] a new byte array

cloneByteArray

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public static byte[] cloneByteArray(byte[] b)

Create a new byte array and copy all the data. If the size of the byte array is zero, the same array is returned.

Parameters

b:byte[]: the byte array (may not be null)

Returns:byte[]

a new byte array

collectGarbage	back to summary
public static synchronized void collectGarbage() Run Java memory garbage collection.

compareSecure	back to summary
public static boolean compareSecure(byte[] test, byte[] good) Compare two byte arrays. This method will always loop over all bytes and doesn't use conditional operations in the loop to make sure an attacker can not use a timing attack when trying out passwords. Parameters test:byte[] the first array good:byte[] the second array Returns:boolean true if both byte arrays contain the same bytes

compareSecure

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public static boolean compareSecure(byte[] test, byte[] good)

Compare two byte arrays. This method will always loop over all bytes and doesn't use conditional operations in the loop to make sure an attacker can not use a timing attack when trying out passwords.

Parameters

test:byte[]: the first array
good:byte[]: the second array

Returns:boolean

true if both byte arrays contain the same bytes

copy	back to summary
public static byte[] copy(byte[] source, byte[] target) Copy the contents of the source array to the target array. If the size if the target array is too small, a larger array is created. Parameters source:byte[] the source array target:byte[] the target array Returns:byte[] the target array or a new one if the target array was too small

copy

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public static byte[] copy(byte[] source, byte[] target)

Copy the contents of the source array to the target array. If the size if the target array is too small, a larger array is created.

Parameters

source:byte[]: the source array
target:byte[]: the target array

Returns:byte[]

the target array or a new one if the target array was too small

copyBytes back to summary

copyBytes	back to summary
public static byte[] copyBytes(byte[] bytes, int len) Creates a copy of array of bytes with the new size. If this is not possible because not enough memory is available, an OutOfMemoryError with the requested size in the message is thrown. This method should be used if the size of the array is user defined, or stored in a file, so wrong size data can be distinguished from regular out-of-memory. Parameters bytes:byte[] source array len:int the number of bytes in the new array Returns:byte[] the byte array Exceptions OutOfMemoryError: if the allocation was too large See Also `Arrays#copyOf(byte[], int)`

public static byte[] copyBytes(byte[] bytes, int len)

Creates a copy of array of bytes with the new size. If this is not possible because not enough memory is available, an OutOfMemoryError with the requested size in the message is thrown.

This method should be used if the size of the array is user defined, or stored in a file, so wrong size data can be distinguished from regular out-of-memory.

Parameters

bytes:byte[]: source array
len:int: the number of bytes in the new array

Returns:byte[]

the byte array

Exceptions

OutOfMemoryError:: if the allocation was too large

See Also

Arrays#copyOf(byte[], int)

createSingleThreadExecutor	back to summary
public static ThreadPoolExecutor createSingleThreadExecutor(String threadName)

createSingleThreadExecutor	back to summary
public static ThreadPoolExecutor createSingleThreadExecutor(String threadName, BlockingQueue<Runnable> workQueue)

currentNanoTime back to summary

currentNanoTime	back to summary
public static long currentNanoTime() Returns the current value of the high-resolution time source. Returns:long time in nanoseconds, never equal to 0 See Also `System#nanoTime()`

public static long currentNanoTime()

Returns the current value of the high-resolution time source.

Returns:long: time in nanoseconds, never equal to 0
See Also: System#nanoTime()

currentNanoTimePlusMillis back to summary

currentNanoTimePlusMillis	back to summary
public static long currentNanoTimePlusMillis(int ms) Returns the current value of the high-resolution time source plus the specified offset. Parameters ms:int additional offset in milliseconds Returns:long time in nanoseconds, never equal to 0 See Also `System#nanoTime()`

public static long currentNanoTimePlusMillis(int ms)

Returns the current value of the high-resolution time source plus the specified offset.

Parameters

ms:int: additional offset in milliseconds

Returns:long

time in nanoseconds, never equal to 0

See Also

System#nanoTime()

flushExecutor	back to summary
public static void flushExecutor(ThreadPoolExecutor executor) Makes sure that all currently submitted tasks are processed before this method returns. It is assumed that there will be no new submissions to this executor, once this method has started. It is assumed that executor is single-threaded, and flush is done by submitting a dummy task and waiting for its completion. Parameters executor:ThreadPoolExecutor to flush

flushExecutor

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public static void flushExecutor(ThreadPoolExecutor executor)

Makes sure that all currently submitted tasks are processed before this method returns. It is assumed that there will be no new submissions to this executor, once this method has started. It is assumed that executor is single-threaded, and flush is done by submitting a dummy task and waiting for its completion.

Parameters

executor:ThreadPoolExecutor: to flush

getByteArrayHash	back to summary
public static int getByteArrayHash(byte[] value) Calculate the hash code of the given byte array. Parameters value:byte[] the byte array Returns:int the hash code

getByteArrayHash

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public static int getByteArrayHash(byte[] value)

Calculate the hash code of the given byte array.

Parameters

value:byte[]: the byte array

Returns:int

the hash code

getGarbageCollectionCount	back to summary
public static long getGarbageCollectionCount()

getGarbageCollectionTime	back to summary
public static long getGarbageCollectionTime()

getMemoryFree	back to summary
public static long getMemoryFree() Get the free memory in KB. This method possibly calls System.gc(). Returns:long the free memory

getMemoryFree

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public static long getMemoryFree()

Get the free memory in KB. This method possibly calls System.gc().

Returns:long: the free memory

getMemoryMax	back to summary
public static long getMemoryMax() Get the maximum memory in KB. Returns:long the maximum memory

getMemoryMax

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public static long getMemoryMax()

Get the maximum memory in KB.

Returns:long: the maximum memory

getMemoryUsed	back to summary
public static long getMemoryUsed() Get the used memory in KB. This method possibly calls System.gc(). Returns:long the used memory

getMemoryUsed

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public static long getMemoryUsed()

Get the used memory in KB. This method possibly calls System.gc().

Returns:long: the used memory

getNonPrimitiveClass	back to summary
public static Class<?> getNonPrimitiveClass(Class<?> clazz) Convert primitive class names to java.lang.* class names. Parameters clazz:Class<?> the class (for example: int) Returns:Class<?> the non-primitive class (for example: java.lang.Integer)

getNonPrimitiveClass

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public static Class<?> getNonPrimitiveClass(Class<?> clazz)

Convert primitive class names to java.lang.* class names.

Parameters

clazz:Class<?>: the class (for example: int)

Returns:Class<?>

the non-primitive class (for example: java.lang.Integer)

getProperty	back to summary
public static String getProperty(String key, String defaultValue) Get the system property. If the system property is not set, or if a security exception occurs, the default value is returned. Parameters key:String the key defaultValue:String the default value Returns:String the value

getProperty

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public static String getProperty(String key, String defaultValue)

Get the system property. If the system property is not set, or if a security exception occurs, the default value is returned.

Parameters

key:String: the key
defaultValue:String: the default value

Returns:String

the value

getProperty	back to summary
public static int getProperty(String key, int defaultValue) Get the system property. If the system property is not set, or if a security exception occurs, the default value is returned. Parameters key:String the key defaultValue:int the default value Returns:int the value

getProperty

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public static int getProperty(String key, int defaultValue)

Get the system property. If the system property is not set, or if a security exception occurs, the default value is returned.

Parameters

key:String: the key
defaultValue:int: the default value

Returns:int

the value

getProperty	back to summary
public static boolean getProperty(String key, boolean defaultValue) Get the system property. If the system property is not set, or if a security exception occurs, the default value is returned. Parameters key:String the key defaultValue:boolean the default value Returns:boolean the value

getProperty

back to summary

public static boolean getProperty(String key, boolean defaultValue)

Get the system property. If the system property is not set, or if a security exception occurs, the default value is returned.

Parameters

key:String: the key
defaultValue:boolean: the default value

Returns:boolean

the value

getResource	back to summary
public static byte[] getResource(String name) throws IOException Get a resource from the resource map. Parameters name:String the name of the resource Returns:byte[] the resource data Exceptions IOException: on failure

getResource

back to summary

public static byte[] getResource(String name) throws IOException

Get a resource from the resource map.

Parameters

name:String: the name of the resource

Returns:byte[]

the resource data

Exceptions

IOException:: on failure

indexOf	back to summary
public static int indexOf(byte[] bytes, byte[] pattern, int start) Calculate the index of the first occurrence of the pattern in the byte array, starting with the given index. This methods returns -1 if the pattern has not been found, and the start position if the pattern is empty. Parameters bytes:byte[] the byte array pattern:byte[] the pattern start:int the start index from where to search Returns:int the index

indexOf

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public static int indexOf(byte[] bytes, byte[] pattern, int start)

Calculate the index of the first occurrence of the pattern in the byte array, starting with the given index. This methods returns -1 if the pattern has not been found, and the start position if the pattern is empty.

Parameters

bytes:byte[]: the byte array
pattern:byte[]: the pattern
start:int: the start index from where to search

Returns:int

the index

loadResource	back to summary
private static byte[] loadResource(String name) throws IOException

match	back to summary
private static int match(Class<?>[] params, Object[] values)

nanoTimePlusMillis back to summary

nanoTimePlusMillis	back to summary
public static long nanoTimePlusMillis(long nanoTime, int ms) Returns the current value of the high-resolution time source plus the specified offset. Parameters nanoTime:long time in nanoseconds ms:int additional offset in milliseconds Returns:long time in nanoseconds, never equal to 0 See Also `System#nanoTime()`

public static long nanoTimePlusMillis(long nanoTime, int ms)

Returns the current value of the high-resolution time source plus the specified offset.

Parameters

nanoTime:long: time in nanoseconds
ms:int: additional offset in milliseconds

Returns:long

time in nanoseconds, never equal to 0

See Also

System#nanoTime()

newBytes	back to summary
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. This method should be used if the size of the array is user defined, or stored in a file, so wrong size data can be distinguished from regular out-of-memory. Parameters len:int the number of bytes requested Returns:byte[] the byte array Exceptions OutOfMemoryError: if the allocation was too large

newBytes

back to summary

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.

This method should be used if the size of the array is user defined, or stored in a file, so wrong size data can be distinguished from regular out-of-memory.

Parameters

len:int: the number of bytes requested

Returns:byte[]

the byte array

Exceptions

OutOfMemoryError:: if the allocation was too large

newInstance	back to summary
public static Object newInstance(String className, Object... params) throws Exception Creates a new instance. This will try to use the constructor where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases). Parameters className:String a string with the entire class, eg. "java.lang.Integer" params:Object[] the constructor parameters Returns:Object the newly created object Exceptions Exception: on failure

newInstance

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public static Object newInstance(String className, Object... params) throws Exception

Creates a new instance. This will try to use the constructor where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases).

Parameters

className:String: a string with the entire class, eg. "java.lang.Integer"
params:Object[]: the constructor parameters

Returns:Object

the newly created object

Exceptions

Exception:: on failure

newSmallArrayList	back to summary
public static <T> ArrayList<T> newSmallArrayList() Create a new ArrayList with an initial capacity of 4. Parameters <T> the type Returns:ArrayList<T> the object

newSmallArrayList

back to summary

public static <T> ArrayList<T> newSmallArrayList()

Create a new ArrayList with an initial capacity of 4.

Parameters

<T>: the type

Returns:ArrayList<T>

the object

parseBoolean back to summary

parseBoolean	back to summary
public static boolean parseBoolean(String value, boolean defaultValue, boolean throwException) Parses the specified string to boolean value. Parameters value:String string to parse defaultValue:boolean value to return if value is null or on parsing error throwException:boolean throw exception on parsing error or return default value instead Returns:boolean parsed or default value Exceptions IllegalArgumentException: on parsing error if `throwException` is true

public static boolean parseBoolean(String value, boolean defaultValue, boolean throwException)

Parses the specified string to boolean value.

Parameters

value:String: string to parse
defaultValue:boolean: value to return if value is null or on parsing error
throwException:boolean: throw exception on parsing error or return default value instead

Returns:boolean

parsed or default value

Exceptions

IllegalArgumentException:: on parsing error if throwException is true

partialQuickSort back to summary

partialQuickSort	back to summary
private static <X> void partialQuickSort(X[] array, int low, int high, Comparator<? super X> comp, int start, int end) Partial quick sort. Works with elements from `low` to `high` indexes, inclusive. Moves smallest elements to `low..start-1` positions and largest elements to `end+1..high` positions. Middle elements are placed into `start..end` positions. All these regions aren't fully sorted. Parameters <X> the type of elements array:X[] the array to sort low:int the lower index with data, inclusive high:int the higher index with data, inclusive, `high > low` comp:Comparator<? super X> the comparator start:int the start index of requested region, inclusive end:int the end index of requested region, inclusive, `end >= start`

private static <X> void partialQuickSort(X[] array, int low, int high, Comparator<? super X> comp, int start, int end)

Partial quick sort.

Works with elements from low to high indexes, inclusive.

Moves smallest elements to low..start-1 positions and largest elements to end+1..high positions. Middle elements are placed into start..end positions. All these regions aren't fully sorted.

Parameters

<X>: the type of elements
array:X[]: the array to sort
low:int: the lower index with data, inclusive
high:int: the higher index with data, inclusive, high > low
comp:Comparator<? super X>: the comparator
start:int: the start index of requested region, inclusive
end:int: the end index of requested region, inclusive, end >= start

scaleForAvailableMemory	back to summary
public static int scaleForAvailableMemory(int value) Scale the value with the available memory. If 1 GB of RAM is available, the value is returned, if 2 GB are available, then twice the value, and so on. Parameters value:int the value to scale Returns:int the scaled value

scaleForAvailableMemory

back to summary

public static int scaleForAvailableMemory(int value)

Scale the value with the available memory. If 1 GB of RAM is available, the value is returned, if 2 GB are available, then twice the value, and so on.

Parameters

value:int: the value to scale

Returns:int

the scaled value

shutdownExecutor	back to summary
public static void shutdownExecutor(ThreadPoolExecutor executor)

sortTopN	back to summary
public static <X> void sortTopN(X[] array, int fromInclusive, int toExclusive, Comparator<? super X> comp) Find the top limit values using given comparator and place them as in a full array sort, in descending order. Parameters <X> the type of elements array:X[] the array. fromInclusive:int the start index, inclusive toExclusive:int the end index, exclusive comp:Comparator<? super X> the comparator.

sortTopN

back to summary

public static <X> void sortTopN(X[] array, int fromInclusive, int toExclusive, Comparator<? super X> comp)

Find the top limit values using given comparator and place them as in a full array sort, in descending order.

Parameters

<X>: the type of elements
array:X[]: the array.
fromInclusive:int: the start index, inclusive
toExclusive:int: the end index, exclusive
comp:Comparator<? super X>: the comparator.

Modifier and Type	Method and Description
public Class<?>	Returns: the class object loadClass(String the binary name of the class name) Load the class.
public boolean	Returns: true if this factory can return a valid class for the provided class name match(String the binary name of the class name) Check whether the factory can return the named class.

public Class Utils

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

public Interface Utils.ClassFactory

Method Summary

Method Detail