程序包 com.alibaba.nacos.common.utils

类 CollectionUtils

  • public final class CollectionUtils
extends java.lang.Object
    Copy from org.apache.commons.collections.
    作者:
    liaochuntao

    • 方法概要

      所有方法 静态方法 具体方法 
      修饰符和类型 方法 说明
      private static <T> java.lang.String buildExceptionMessage​(java.util.Iterator<T> iterator, T first)  
      static <T> boolean contains​(java.util.Collection<T> coll, T target)
      Whether contain item in collection.
      static java.lang.Object get​(java.lang.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​(java.lang.Iterable<T> iterable)
      return the first element, if the iterator contains multiple elements, will throw IllegalArgumentException.
      static <T> T getOrDefault​(java.lang.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​(java.util.Collection coll)
      Null-safe check if the specified collection is empty.
      static boolean isMapEmpty​(java.util.Map<?,​?> map)
      Return true if the supplied Map is null or empty.
      static boolean isNotEmpty​(java.util.Collection coll)
      Null-safe check if the specified collection is not empty.
      static <T> java.util.List<T> list​(T... elements)
      return an arraylist containing all input parameters.
      static <T> java.util.Set<T> set​(T... elements)
      Return an set containing all input parameters.
      static int size​(java.lang.Object object)
      Gets the size of the collection/iterator specified.
      static boolean sizeIsEmpty​(java.lang.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

    • 构造器详细资料

      • CollectionUtils

        public CollectionUtils()

    • 方法详细资料

      • get

        public static java.lang.Object get​(java.lang.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:
        java.lang.IndexOutOfBoundsException - if the index is invalid
        java.lang.IllegalArgumentException - if the object type is invalid

      • size

        public static int size​(java.lang.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:
        java.lang.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​(java.lang.Object object)
        Judge whether object is empty.
        参数:
        object - object
        返回:
        true if object is empty, otherwise false
        抛出:
        java.lang.IllegalArgumentException - if object has no length or size

      • contains

        public static <T> boolean contains​(java.util.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​(java.util.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​(java.util.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​(java.lang.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> java.util.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> java.util.Set<T> set​(T... elements)
        Return an set containing all input parameters.
        参数:
        elements - elements element array
        返回:
        set containing all input parameters

      • getOnlyElement

        public static <T> T getOnlyElement​(java.lang.Iterable<T> iterable)
        return the first element, if the iterator contains multiple elements, will throw IllegalArgumentException.
        抛出:
        java.util.NoSuchElementException - if the iterator is empty
        java.lang.IllegalArgumentException - if the iterator contains multiple elements. The state of the iterator is unspecified.

      • buildExceptionMessage

        private static <T> java.lang.String buildExceptionMessage​(java.util.Iterator<T> iterator,
                                                          T first)

      • isMapEmpty

        public static boolean isMapEmpty​(java.util.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