org.mapdb

Class Fun

java.lang.Object

org.mapdb.Fun

public final class Fun
extends Object

Functional stuff. Tuples, function, callback methods etc..

Author:

Jan Kotek

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Fun.ArrayComparator compares two arrays using given comparators
static interface	Fun.Function0<R> function which takes no argument and returns one value
static interface	Fun.Function1<R,A> function which takes one argument and returns one value
static interface	Fun.Function1Int<R> function which takes one int argument and returns one value
static interface	Fun.Function2<R,A,B> function which takes two argument and returns one value
static class	Fun.Pair<A,B>
static interface	Fun.RecordCondition<A> decides if some action should be executed on an record

Field Summary

Fields

Modifier and Type	Field and Description
static Comparator<byte[]>	BYTE_ARRAY_COMPARATOR
static Comparator<char[]>	CHAR_ARRAY_COMPARATOR
static Comparator<Object[]>	COMPARABLE_ARRAY_COMPARATOR Compares two arrays which contains comparable elements
static Comparator	COMPARATOR
static Comparator<double[]>	DOUBLE_ARRAY_COMPARATOR
static Iterator	EMPTY_ITERATOR
static Comparator<int[]>	INT_ARRAY_COMPARATOR
static Comparator<long[]>	LONG_ARRAY_COMPARATOR
static Object	PLACEHOLDER place holder for some stuff in future
static Fun.RecordCondition	RECORD_ALWAYS_TRUE record condition which always returns true
static Comparator	REVERSE_COMPARATOR

Method Summary

Methods

Modifier and Type	Method and Description
static boolean	arrayContains(long[] longs, long val)
static <T> Comparator<T>	comparator() A utility method for getting a type-safe Comparator, it provides type-inference help.
static int	compareInt(int x, int y)
static int	compareLong(long x, long y)
static <T> Iterator<T>	emptyIterator()
static boolean	eq(Object a, Object b) returns true if all elements are equal, works with nulls
static <K,V> Fun.Function1<K,Fun.Pair<K,V>>	extractKey()
static <K,V> Fun.Function1<K,Map.Entry<K,V>>	extractMapEntryKey()
static <K,V> Fun.Function1<V,Map.Entry<K,V>>	extractMapEntryValue()
static <K> Fun.Function1<K,K>	extractNoTransform() returns function which always returns the value itself without transformation
static <K,V> Fun.Function1<V,Fun.Pair<K,V>>	extractValue()
static Iterable<Object[]>	filter(NavigableSet<Object[]> set, Object... keys) TODO document tuples Find all Primary Keys associated with Secondary Key.
static <T> Comparator<T>	reverseComparator() A utility method for getting a type-safe reversed Comparator (the negation of comparator()).
static long	roundDown(long number, long roundDownToMultipleOf)
static long	roundUp(long number, long roundUpToMultipleOf)

Methods inherited from class java.lang.Object

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

Field Detail

PLACEHOLDER

public static final Object PLACEHOLDER

place holder for some stuff in future

COMPARATOR

public static final Comparator COMPARATOR

REVERSE_COMPARATOR

public static final Comparator REVERSE_COMPARATOR

EMPTY_ITERATOR

public static final Iterator EMPTY_ITERATOR

BYTE_ARRAY_COMPARATOR

public static final Comparator<byte[]> BYTE_ARRAY_COMPARATOR

CHAR_ARRAY_COMPARATOR

public static final Comparator<char[]> CHAR_ARRAY_COMPARATOR

INT_ARRAY_COMPARATOR

public static final Comparator<int[]> INT_ARRAY_COMPARATOR

LONG_ARRAY_COMPARATOR

public static final Comparator<long[]> LONG_ARRAY_COMPARATOR

DOUBLE_ARRAY_COMPARATOR

public static final Comparator<double[]> DOUBLE_ARRAY_COMPARATOR

COMPARABLE_ARRAY_COMPARATOR

public static final Comparator<Object[]> COMPARABLE_ARRAY_COMPARATOR

Compares two arrays which contains comparable elements

RECORD_ALWAYS_TRUE

public static final Fun.RecordCondition RECORD_ALWAYS_TRUE

record condition which always returns true

Method Detail

comparator

public static <T> Comparator<T> comparator()

A utility method for getting a type-safe Comparator, it provides type-inference help. Use this method instead of COMPARATOR in order to insure type-safety ex: Comparator<Integer> comparator = getComparator();

Returns:

comparator

reverseComparator

public static <T> Comparator<T> reverseComparator()

A utility method for getting a type-safe reversed Comparator (the negation of comparator()). Use this method instead of REVERSE_COMPARATOR in order to insure type-safety ex: Comparator<Integer> comparator = getReversedComparator();

Returns:

comparator

emptyIterator

public static <T> Iterator<T> emptyIterator()

eq

public static boolean eq(Object a,
         Object b)

returns true if all elements are equal, works with nulls

roundUp

public static long roundUp(long number,
           long roundUpToMultipleOf)

roundDown

public static long roundDown(long number,
             long roundDownToMultipleOf)

arrayContains

public static boolean arrayContains(long[] longs,
                    long val)

extractKey

public static <K,V> Fun.Function1<K,Fun.Pair<K,V>> extractKey()

extractValue

public static <K,V> Fun.Function1<V,Fun.Pair<K,V>> extractValue()

extractMapEntryKey

public static <K,V> Fun.Function1<K,Map.Entry<K,V>> extractMapEntryKey()

extractMapEntryValue

public static <K,V> Fun.Function1<V,Map.Entry<K,V>> extractMapEntryValue()

extractNoTransform

public static <K> Fun.Function1<K,K> extractNoTransform()

returns function which always returns the value itself without transformation

compareInt

public static int compareInt(int x,
             int y)

compareLong

public static int compareLong(long x,
              long y)

filter

public static Iterable<Object[]> filter(NavigableSet<Object[]> set,
                        Object... keys)

TODO document tuples Find all Primary Keys associated with Secondary Key. This is useful companion to Bind.mapInverse(org.mapdb.Bind.MapWithModificationListener, java.util.Set) and Bind.secondaryKey(org.mapdb.Bind.MapWithModificationListener, java.util.Set, org.mapdb.Fun.Function2) It can by also used to find values from 'MultiMap'.

Parameters:

set - Set or 'MultiMap' to find values in

keys - key to look from

Returns:

all keys where primary value equals to secondaryKey