org.h2.util

Class Utils

java.lang.Object

org.h2.util.Utils

public class Utils
extends java.lang.Object

This utility class contains miscellaneous functions.

Nested Class Summary

Nested Classes

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

Field Summary

Fields

Modifier and Type	Field and Description
static byte[]	EMPTY_BYTES An 0-size byte array.
static int[]	EMPTY_INT_ARRAY An 0-size int array.

Method Summary

Methods

Modifier and Type	Method and Description
static java.lang.Object	callMethod(java.lang.Object instance, java.lang.String methodName, java.lang.Object... params) Calls an instance method via reflection.
static java.lang.Object	callStaticMethod(java.lang.String classAndMethod, java.lang.Object... params) Calls a static method via reflection.
static byte[]	cloneByteArray(byte[] b) Create a new byte array and copy all the data.
static int	compareNotNullSigned(byte[] data1, byte[] data2) Compare the contents of two byte arrays.
static int	compareNotNullUnsigned(byte[] data1, byte[] data2) Compare the contents of two byte arrays.
static boolean	compareSecure(byte[] test, byte[] good) Compare two byte arrays.
static byte[]	copy(byte[] source, byte[] target) Copy the contents of the source array to the target array.
static int	getByteArrayHash(byte[] value) Calculate the hash code of the given byte array.
static java.lang.Object	getField(java.lang.Object instance, java.lang.String fieldName) Returns a static field.
static int	getMemoryFree() Get the free memory in KB.
static long	getMemoryMax() Get the maximum memory in KB.
static int	getMemoryUsed() Get the used memory in KB.
static java.lang.Class<?>	getNonPrimitiveClass(java.lang.Class<?> clazz) Convert primitive class names to java.lang.* class names.
static boolean	getProperty(java.lang.String key, boolean defaultValue) Get the system property.
static int	getProperty(java.lang.String key, int defaultValue) Get the system property.
static java.lang.String	getProperty(java.lang.String key, java.lang.String defaultValue) Get the system property.
static byte[]	getResource(java.lang.String name) Get a resource from the resource map.
static java.lang.Object	getStaticField(java.lang.String classAndField) Returns a static field.
static int	hashCode(java.lang.Object o) Calculate the hash code of the given object.
static boolean	haveCommonComparableSuperclass(java.lang.Class<?> c1, java.lang.Class<?> c2) Checks if given classes have a common Comparable superclass.
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.
static boolean	isClassPresent(java.lang.String fullyQualifiedClassName) Returns true if the class is present in the current class loader.
static java.lang.Object	newInstance(java.lang.String className, java.lang.Object... params) Creates a new instance.
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.
static long	readLong(byte[] buff, int pos) Read a long value from the byte array at the given position.
static int	scaleForAvailableMemory(int value) Scale the value with the available memory.
static <X> void	sortTopN(X[] array, int offset, int limit, java.util.Comparator<? super X> comp) Find the top limit values using given comparator and place them as in a full array sort, in descending order.
static void	writeLong(byte[] buff, int pos, long x) Write a long value to the byte array at the given position.

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.

Method Detail

writeLong

public static void writeLong(byte[] buff,
             int pos,
             long x)

Write a long value to the byte array at the given position. The most significant byte is written first.

Parameters:

buff - the byte array

pos - the position

x - the value to write

readLong

public static long readLong(byte[] buff,
            int pos)

Read a long value from the byte array at the given position. The most significant byte is read first.

Parameters:

buff - the byte array

pos - the position

Returns:

the value

indexOf

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 - the byte array

pattern - the pattern

start - the start index from where to search

Returns:

the index

getByteArrayHash

public static int getByteArrayHash(byte[] value)

Calculate the hash code of the given byte array.

Parameters:

value - the byte array

Returns:

the hash code

compareSecure

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 - the first array

good - the second array

Returns:

true if both byte arrays contain the same bytes

compareNotNullSigned

public static int compareNotNullSigned(byte[] data1,
                       byte[] data2)

Compare the contents of two byte arrays. If the content or length of the first array is smaller than the second array, -1 is returned. If the content or length of the second array is smaller than the first array, 1 is returned. If the contents and lengths are the same, 0 is returned.

This method interprets bytes as signed.

Parameters:

data1 - the first byte array (must not be null)

data2 - the second byte array (must not be null)

Returns:

the result of the comparison (-1, 1 or 0)

compareNotNullUnsigned

public static int compareNotNullUnsigned(byte[] data1,
                         byte[] data2)

Compare the contents of two byte arrays. If the content or length of the first array is smaller than the second array, -1 is returned. If the content or length of the second array is smaller than the first array, 1 is returned. If the contents and lengths are the same, 0 is returned.

This method interprets bytes as unsigned.

Parameters:

data1 - the first byte array (must not be null)

data2 - the second byte array (must not be null)

Returns:

the result of the comparison (-1, 1 or 0)

copy

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 - the source array

target - the target array

Returns:

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

cloneByteArray

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 - the byte array (may not be null)

Returns:

a new byte array

hashCode

public static int hashCode(java.lang.Object o)

Calculate the hash code of the given object. The object may be null.

Parameters:

o - the object

Returns:

the hash code, or 0 if the object is null

getMemoryUsed

public static int getMemoryUsed()

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

Returns:

the used memory

getMemoryFree

public static int getMemoryFree()

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

Returns:

the free memory

getMemoryMax

public static long getMemoryMax()

Get the maximum memory in KB.

Returns:

the maximum memory

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

sortTopN

public static <X> void sortTopN(X[] array,
                int offset,
                int limit,
                java.util.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:

array - the array.

offset - the offset.

limit - the limit.

comp - the comparator.

haveCommonComparableSuperclass

public static boolean haveCommonComparableSuperclass(java.lang.Class<?> c1,
                                     java.lang.Class<?> c2)

Checks if given classes have a common Comparable superclass.

Parameters:

c1 - the first class

c2 - the second class

Returns:

true if they have

getResource

public static byte[] getResource(java.lang.String name)
                          throws java.io.IOException

Get a resource from the resource map.

Parameters:

name - the name of the resource

Returns:

the resource data

Throws:

java.io.IOException

callStaticMethod

public static java.lang.Object callStaticMethod(java.lang.String classAndMethod,
                                java.lang.Object... params)
                                         throws java.lang.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 - a string with the entire class and method name, eg. "java.lang.System.gc"

params - the method parameters

Returns:

the return value from this call

Throws:

java.lang.Exception

callMethod

public static java.lang.Object callMethod(java.lang.Object instance,
                          java.lang.String methodName,
                          java.lang.Object... params)
                                   throws java.lang.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 - the instance on which the call is done

methodName - a string with the method name

params - the method parameters

Returns:

the return value from this call

Throws:

java.lang.Exception

newInstance

public static java.lang.Object newInstance(java.lang.String className,
                           java.lang.Object... params)
                                    throws java.lang.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 - a string with the entire class, eg. "java.lang.Integer"

params - the constructor parameters

Returns:

the newly created object

Throws:

java.lang.Exception

getStaticField

public static java.lang.Object getStaticField(java.lang.String classAndField)
                                       throws java.lang.Exception

Returns a static field.

Parameters:

classAndField - a string with the entire class and field name

Returns:

the field value

Throws:

java.lang.Exception

getField

public static java.lang.Object getField(java.lang.Object instance,
                        java.lang.String fieldName)
                                 throws java.lang.Exception

Returns a static field.

Parameters:

instance - the instance on which the call is done

fieldName - the field name

Returns:

the field value

Throws:

java.lang.Exception

isClassPresent

public static boolean isClassPresent(java.lang.String fullyQualifiedClassName)

Returns true if the class is present in the current class loader.

Parameters:

fullyQualifiedClassName - a string with the entire class name, eg. "java.lang.System"

Returns:

true if the class is present

getNonPrimitiveClass

public static java.lang.Class<?> getNonPrimitiveClass(java.lang.Class<?> clazz)

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

Parameters:

clazz - the class (for example: int)

Returns:

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

getProperty

public static java.lang.String getProperty(java.lang.String key,
                           java.lang.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 - the key

defaultValue - the default value

Returns:

the value

getProperty

public static int getProperty(java.lang.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 - the key

defaultValue - the default value

Returns:

the value

getProperty

public static boolean getProperty(java.lang.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 - the key

defaultValue - the default value

Returns:

the value

scaleForAvailableMemory

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 - the value to scale

Returns:

the scaled value