com.alibaba.nacos.common.utils

类 CollectionUtils

java.lang.Object

com.alibaba.nacos.common.utils.CollectionUtils

public final class CollectionUtils
extends Object

Copy from org.apache.commons.collections.

作者:

liaochuntao

方法概要

限定符和类型	方法和说明
static <T> boolean	contains(Collection<T> coll, T target) Whether contain item in collection.
static Object	get(Object object, int index) Returns the index-th value in object, throwing IndexOutOfBoundsException if there is no such element or IllegalArgumentException if object is not an instance of one of the supported types.
static <T> T	getOnlyElement(Iterable<T> iterable) return the first element, if the iterator contains multiple elements, will throw IllegalArgumentException.
static <T> T	getOrDefault(Object obj, int index, T defaultValue) Returns the value to which the specified index , or defaultValue if this collection contains no value for the index.
static boolean	isEmpty(Collection coll) Null-safe check if the specified collection is empty.
static boolean	isListEqual(List<String> firstList, List<String> secondList) check list is equal.
static boolean	isMapEmpty(Map<?,?> map) Return true if the supplied Map is null or empty.
static boolean	isNotEmpty(Collection coll) Null-safe check if the specified collection is not empty.
static <T> List<T>	list(T... elements) return an arraylist containing all input parameters.
static <T> Set<T>	set(T... elements) Return a set containing all input parameters.
static int	size(Object object) Gets the size of the collection/iterator specified.
static boolean	sizeIsEmpty(Object object) Judge whether object is empty.

从类继承的方法 java.lang.Object

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

方法详细资料

get

public static Object get(Object object,
                         int index)

Returns the index-th value in object, throwing IndexOutOfBoundsException if there is no such element or IllegalArgumentException if object is not an instance of one of the supported types.

The supported types, and associated semantics are:

• Map -- the value returned is the Map.Entry in position index in the map's entrySet iterator, if there is such an entry.
• List -- this method is equivalent to the list's get method.
• Array -- the index-th array entry is returned, if there is such an entry; otherwise an IndexOutOfBoundsException is thrown.
• Collection -- the value returned is the index-th object returned by the collection's default iterator, if there is such an element.
• Iterator or Enumeration -- the value returned is the index-th object in the Iterator/Enumeration, if there is such an element. The Iterator/Enumeration is advanced to index (or to the end, if index exceeds the number of entries) as a side effect of this method.

参数:

object - the object to get a value from

index - the index to get

返回:

the object at the specified index

抛出:

IndexOutOfBoundsException - if the index is invalid

IllegalArgumentException - if the object type is invalid

size

public static int size(Object object)

Gets the size of the collection/iterator specified.

This method can handles objects as follows

• Collection - the collection size
• Map - the map size
• Array - the array size
• Iterator - the number of elements remaining in the iterator
• Enumeration - the number of elements remaining in the enumeration

参数:

object - the object to get the size of

返回:

the size of the specified collection

抛出:

IllegalArgumentException - thrown if object is not recognised or null

从以下版本开始:

Commons Collections 3.1

sizeIsEmpty

public static boolean sizeIsEmpty(Object object)

Judge whether object is empty.

参数:

object - object

返回:

true if object is empty, otherwise false

抛出:

IllegalArgumentException - if object has no length or size

contains

public static <T> boolean contains(Collection<T> coll,
                                   T target)

Whether contain item in collection.

类型参数:

T - General Type

参数:

coll - collection

target - target value

返回:

true if contain, otherwise false

isEmpty

public static boolean isEmpty(Collection coll)

Null-safe check if the specified collection is empty.

Null returns true.

参数:

coll - the collection to check, may be null

返回:

true if empty or null

从以下版本开始:

Commons Collections 3.2

isNotEmpty

public static boolean isNotEmpty(Collection coll)

Null-safe check if the specified collection is not empty.

Null returns false.

参数:

coll - the collection to check, may be null

返回:

true if non-null and non-empty

从以下版本开始:

Commons Collections 3.2

getOrDefault

public static <T> T getOrDefault(Object obj,
                                 int index,
                                 T defaultValue)

Returns the value to which the specified index , or defaultValue if this collection contains no value for the index.

类型参数:

T - General Type

参数:

obj - the object to get a value from

index - the index to get

defaultValue - default value

返回:

the value to which the specified index , or defaultValue if this collection contains no value for the index.

list

public static <T> List<T> list(T... elements)

return an arraylist containing all input parameters.

参数:

elements - element array

返回:

arraylist containing all input parameters

set

public static <T> Set<T> set(T... elements)

Return a set containing all input parameters.

参数:

elements - elements element array

返回:

set containing all input parameters

getOnlyElement

public static <T> T getOnlyElement(Iterable<T> iterable)

return the first element, if the iterator contains multiple elements, will throw IllegalArgumentException.

抛出:

NoSuchElementException - if the iterator is empty

IllegalArgumentException - if the iterator contains multiple elements. The state of the iterator is unspecified.

isListEqual

public static boolean isListEqual(List<String> firstList,
                                  List<String> secondList)

check list is equal.

参数:

firstList - first list.

secondList - second list.

返回:

isMapEmpty

public static boolean isMapEmpty(Map<?,?> map)

Return true if the supplied Map is null or empty. Otherwise, return false.

参数:

map - the Map to check

返回:

whether the given Map is empty