Package nl.vpro.util

Class Helper

java.lang.Object

nl.vpro.util.Helper

public class Helper
extends Object

Simple helper methods.

Author:

arne, peter, [email protected]

Method Summary

Modifier and Type	Method	Description
static <K,L extends K,V,W extends V> void	add(Map<K,List<V>> listMap, L key, W value)	Adds a value to a map of lists.
static <K,L extends K,V,W extends V> void	addToSetMap(Map<K,Set<V>> setMap, L key, W value)	Adds a value to a map of sets.
static StringBuilder	appendIfNotEmpty(StringBuilder sb, String s)
static <T> boolean	arrayContains(T element, T... array)	Tries and find an element in an array.
static int	compare(Comparable o1, Comparable o2)	Compare, taking null into account (null <).
static <T> T	firstNonNull(List<T> values)	Returns the first non-null value.
static <T> T	firstNonNull(Set<T> values)	Returns the first non-null value.
static <W extends Annotation> String	getAnnotatedProperty(Class<?> clazz, Class<W> annClazz)
static <T> Class<T>	getClass(String name)
static boolean	isAssignableFrom(Object toTest, String name)
static boolean	isAssignableFrom(String toTest, String name)
static boolean	isNumber(String text)	Determines whether some string is a number.
static <T> String	join(Collection<T> list, String sep)	joins all items in the given list using String.valueOf on each item seperated by the sep String
static <N extends Number> N	numberCast(Number value, Class<N> targetType)	Converts a number to another number, potentially rounding to fit the target type.
static String	nvl(String... values)
static <T> T	nvl(T... values)	Returns the first non-null value.
static <K,V> void	putIfNotNull(Map<K,V> map, K key, V value)	Puts a value in a map when the value is not null.
static <T> List<T>	removeNullEntries(List<T> source)
static <T extends Comparable<? super T>> List<T>	sim(List<T> a, List<T> b)	Determine the similar elements in both lists.
static List<String>	spliceNumber(Number number, int maxPartSize)	Will splice the number in chunks no larger then maxPartSize
static List<String>	spliceNumber(Number number, int minPartSize, int maxPartSize)	Will splice the number in chunks no larger then maxPartSize
static <T> T	toSingleton(List<T> list)	Convert a singleton list into the singleton element.
static <T> T	toSingleton(Set<T> set)	Convert a singleton set into the singleton element.
static int	withDefault(int value, int def)	Gives a default in case the value is -1.
static <T> T	withDefault(T value, T def)	Gives a default in case the value is null.

Methods inherited from class java.lang.Object

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

Method Detail

withDefault

public static <T> T withDefault(T value,
                                T def)

Gives a default in case the value is null.

Type Parameters:

T - the type of the value

Parameters:

value - a value

def - the default

Returns:

value when value is not null, def otherwise

See Also:

nvl(Object[])

withDefault

public static int withDefault(int value,
                              int def)

Gives a default in case the value is -1.

Parameters:

value - a value

def - the default

Returns:

the value if it is not -1, def otherwise

nvl

@SafeVarargs
public static <T> T nvl(T... values)

Returns the first non-null value. This method is also known as coalesce.

Type Parameters:

T - the type of the value

Parameters:

values - the values

Returns:

the first non-null value in the arguments, or null when values is null or when all given values in it are all null

See Also:

withDefault(Object, Object)

nvl

public static String nvl(String... values)

firstNonNull

public static <T> T firstNonNull(List<T> values)

Returns the first non-null value. This method is also known as coalesce.

Parameters:

values - the values

Returns:

the first non-null value in the arguments, or null when values is null or when all given values in it are all null

See Also:

withDefault(Object, Object)

firstNonNull

public static <T> T firstNonNull(Set<T> values)

Returns the first non-null value. This method is also known as coalesce.

Parameters:

values - the values

Returns:

the first non-null value in the arguments, or null when values is null or when all given values in it are all null

See Also:

withDefault(Object, Object)

add

public static <K,L extends K,V,W extends V> void add(Map<K,List<V>> listMap,
                                                                       L key,
                                                                       W value)

Adds a value to a map of lists. A value list is created when there is no entry in the map for the given key.

Type Parameters:

K - key type in the map

L - actual used key type

V - list type in the map

W - actual used list type

Parameters:

listMap - the map of lists (not null)

key - the key (may be null when the map supports null keys)

value - the value to put in the list

addToSetMap

public static <K,L extends K,V,W extends V> void addToSetMap(Map<K,Set<V>> setMap,
                                                                               L key,
                                                                               W value)

Adds a value to a map of sets. A value set is created when there is no entry in the map for the given key.

Type Parameters:

K - key type in the map

L - actual used key type

V - set type in the map

W - actual used set type

Parameters:

setMap - the map of sets (not null)

key - the key (may be null when the map supports null keys)

value - the value to put in the set

putIfNotNull

public static <K,V> void putIfNotNull(Map<K,V> map,
                                            K key,
                                            V value)

Puts a value in a map when the value is not null.

Type Parameters:

K - the key type

V - the value type

Parameters:

map - the map (not null)

key - the key, can be null when the map supports it

value - the value or null to do nothing

isNumber

public static boolean isNumber(String text)

Determines whether some string is a number. No range check is performed.

Parameters:

text - the string of which must be determined if it's a number

Returns:

true if text is a number, false otherwise

numberCast

public static <N extends Number> N numberCast(Number value,
                                              Class<N> targetType)

Converts a number to another number, potentially rounding to fit the target type.

Does all standard java types except Atomic* and Mutable*.

Type Parameters:

N - the target number type

Parameters:

value - the number to convert

targetType - the return type (not null)

Returns:

value cast to type N or null when value is null. Note that the information may be discarded when the value is incompatible with the target type.

arrayContains

@SafeVarargs
public static <T> boolean arrayContains(T element,
                                        T... array)

Tries and find an element in an array. equals is used for comparisons. A linear search is performed - if the input array is sorted, it would be wiser to use Arrays.binarySearch(Object[], Object).

Type Parameters:

T - the array type

Parameters:

element - the element to find

array - the array to search in

Returns:

true if the array contains the element, false otherwise

compare

public static int compare(Comparable o1,
                          Comparable o2)

Compare, taking null into account (null <).

Parameters:

o1 - first

o2 - second

Returns:

1,0,-1

toSingleton

public static <T> T toSingleton(List<T> list)

Convert a singleton list into the singleton element.

Type Parameters:

T - The type of the list

Parameters:

list - the list

Returns:

the singleton in the list, or null if the list is null or the size of the list is zero.

Throws:

IllegalStateException - when more than one element is found in the list.

toSingleton

public static <T> T toSingleton(Set<T> set)

Convert a singleton set into the singleton element.

Type Parameters:

T - The type of the set

Parameters:

set - the set

Returns:

the singleton in the set, or null if the set is null or the size of the set is zero.

Throws:

IllegalStateException - when more than one element is found in the set.

isAssignableFrom

public static boolean isAssignableFrom(Object toTest,
                                       String name)

Parameters:

toTest - The object to test

name - The FQN of the class to test againts. The class should be in the classpath

Returns:

true if the 'name' is assignable from 'toTest'

isAssignableFrom

public static boolean isAssignableFrom(String toTest,
                                       String name)

Parameters:

toTest - The FQN object to test. The class should be in the classpath

name - The FQN of the class to test against. The class should be in the classpath

Returns:

true if the 'name' is assignable from 'toTest'

getClass

public static <T> Class<T> getClass(String name)

getAnnotatedProperty

public static <W extends Annotation> String getAnnotatedProperty(Class<?> clazz,
                                                                 Class<W> annClazz)

removeNullEntries

public static <T> List<T> removeNullEntries(List<T> source)

appendIfNotEmpty

public static StringBuilder appendIfNotEmpty(StringBuilder sb,
                                             String s)

join

public static <T> String join(Collection<T> list,
                              String sep)

joins all items in the given list using String.valueOf on each item seperated by the sep String

Parameters:

list - The list to join

sep - The separator String

Returns:

the result

sim

public static <T extends Comparable<? super T>> List<T> sim(List<T> a,
                                                            List<T> b)

Determine the similar elements in both lists. Result will be sorted.

Parameters:

a - List a

b - List b

Returns:

The similar elements for both lists

spliceNumber

public static List<String> spliceNumber(Number number,
                                        int maxPartSize)

Will splice the number in chunks no larger then maxPartSize

Parameters:

number - The number to splice

maxPartSize - The maximum size of a part in the path

Returns:

A list of the spliced id

spliceNumber

public static List<String> spliceNumber(Number number,
                                        int minPartSize,
                                        int maxPartSize)

Will splice the number in chunks no larger then maxPartSize

Parameters:

number - The number to splice

minPartSize - The minimal size of a part, smaller will be skipped

maxPartSize - The maximum size of a part in the path

Returns:

A list of the spliced id