Package com.norconex.commons.lang.collection

Class CollectionUtil

  • public final class CollectionUtil
extends Object
    Collection-related utility methods.
    Since:
    2.0.0
    Author:
    Pascal Essiembre

    • Method Detail

      • adaptedList

        public static <T> List<T> adaptedList​(Object object)
        Adapts any object to a new non-null mutable List, regardless of the nature of the object. If the object is a Collection or array, it will be iterated over to populate the new list. If it is any other object, it will become the first and only item in the newly created list. If the object is null or a blank string, an empty list is returned. The supplied object must be a value or values of the expected type.
        Type Parameters:
        T - the expected return type of the list
        Parameters:
        object - object to adapt
        Returns:
        adapted list

      • adaptedSet

        public static <T> Set<T> adaptedSet​(Object object)
        Adapts any object to a new non-null mutable Set, regardless of the nature of the object. If the object is a Collection or array, it will be iterated over to populate the new set. If it is any other object, it will become the first and only item in the newly created set. If the object is null or a blank string, an empty set is returned. The supplied object must be a value or values of the expected type.
        Type Parameters:
        T - the expected return type of the set
        Parameters:
        object - object to adapt
        Returns:
        adapted set

      • toArray

        public static Object toArray​(Collection<?> c,
                             @NonNull
                             @NonNull Class<?> arrayType)

        Converts a collection to an array using the specified type (never null).

        Since 3.0.0, passing a null collection argument will will return an empty array of the supplied type.

        Parameters:
        c - collection to convert or null
        arrayType - array type (must not be null)
        Returns:
        the new array (never null)
        Throws:
        NullPointerException - if arrayType is null

      • setAll

        public static <T> void setAll​(Collection<T> target,
                              Collection<T> source)
        Sets all values of the source collection into the target one. Same as doing a "clear", followed by "addAll", but it also checks for null and will not clear/add if the source collection is the same instance as the target one. If target is null, invoking this method has no effect. If source is null will clear the target collection
        Type Parameters:
        T - objects class type
        Parameters:
        target - target collection
        source - source collection

      • setAll

        @SafeVarargs
public static <T> void setAll​(Collection<T> target,
                              T... source)
        Sets all values of the source array into the target collection. Same as doing a "clear", followed by "addAll" after converting the array to a list. It also checks for null. If target is null, invoking this method has no effect. If source is null or is an array containing only one null element, it will clear the target collection
        Type Parameters:
        T - objects class type
        Parameters:
        target - target collection
        source - source collection

      • setAll

        public static <K,​V> void setAll​(Map<K,​V> target,
                                      Map<K,​V> source)
        Sets all values of the source map into the target one. Same as doing a "clear", followed by "putAll", but it also checks for null and will not clear/add if the source map is the same instance as the target one. If target is null, invoking this method has no effect. If source is null will clear the target map
        Type Parameters:
        K - key type
        V - value type
        Parameters:
        target - target map
        source - source map

      • asListOrEmpty

        @SafeVarargs
public static <T> List<T> asListOrEmpty​(T... values)
        Returns a fixed-size list backed by the specified array or an empty list if the array is null. This is a null-safe version of Arrays.asList(Object...).
        Type Parameters:
        T - objects class type
        Parameters:
        values - the array by which the list will be backed
        Returns:
        a list view of the specified array (never null)
        See Also:
        asListOrNull(Object...)

      • asListOrNull

        @SafeVarargs
public static <T> List<T> asListOrNull​(T... values)
        Returns a fixed-size list backed by the specified array or null if the array is null. This is a null-safe version of Arrays.asList(Object...). A list is returned even if the array is empty or contains only null values.
        Type Parameters:
        T - objects class type
        Parameters:
        values - the array by which the list will be backed
        Returns:
        a list view of the specified array
        See Also:
        asListOrEmpty(Object...)

      • toStringList

        public static List<String> toStringList​(Object... values)
        Converts a list of objects to a list of strings using default Converter instance. If the supplied list is null, an empty string list is returned.
        Parameters:
        values - list to convert to a list of strings
        Returns:
        list of strings

      • toStringList

        public static List<String> toStringList​(Collection<?> values)
        Converts a list of objects to a list of strings using default Converter instance. If the supplied list is null, an empty string list is returned.
        Parameters:
        values - list to convert to a list of strings
        Returns:
        list of strings

      • toTypeList

        public static <T> List<T> toTypeList​(List<String> values,
                                     Class<T> targetClass)
        Converts a list of strings to a list of objects matching the return type. If the supplied list is null, an empty list is returned.
        Type Parameters:
        T - objects class type
        Parameters:
        values - list to convert to a list of the given type
        targetClass - target class
        Returns:
        list

      • toTypeList

        public static <T> List<T> toTypeList​(List<String> values,
                                     Function<String,​T> converter)
        Converts a list of strings to a list of objects matching the return type. If the supplied list is null, an empty list is returned.
        Type Parameters:
        T - target objects class type
        Parameters:
        values - list to convert to a list of the given type
        converter - function converting string to type
        Returns:
        list

      • unmodifiableList

        public static <T> List<T> unmodifiableList​(T... values)
        Returns an unmodifiable view of the specified list. Convenience method for doing with an array the same as Collections.unmodifiableList(List). A null array argument will return an empty list.
        Type Parameters:
        T - target objects class type
        Parameters:
        values - the values to convert to an unmodifiable list
        Returns:
        unmodifiable list (never null)

      • unmodifiableSet

        public static <T> Set<T> unmodifiableSet​(T... values)
        Returns an unmodifiable view of the specified set. Convenience method for doing with an array the same as Collections.unmodifiableSet(Set). A null array argument will return an empty set. This method uses a LinkedHashSet to maintain order.
        Type Parameters:
        T - target objects class type
        Parameters:
        values - the values to convert to an unmodifiable list
        Returns:
        unmodifiable list

      • removeNulls

        public static void removeNulls​(Collection<?> c)
        Removes null entries in the given collection. Only useful for collection implementations allowing null entries.
        Parameters:
        c - a collection

      • removeBlanks

        public static void removeBlanks​(Collection<String> c)
        Removes blank strings in the given collection.
        Parameters:
        c - a string collection

      • removeEmpties

        public static void removeEmpties​(Collection<String> c)
        Removes empty strings in the given collection.
        Parameters:
        c - a string collection

      • replaceAll

        public static <T> void replaceAll​(Collection<T> c,
                                  T source,
                                  T target)
        Replaces all elements matching the source value with the target value.
        Type Parameters:
        T - elements type
        Parameters:
        c - a collection
        source - object to replace
        target - replacement

      • nullsToEmpties

        public static void nullsToEmpties​(Collection<String> c)
        Convert null entries to empty strings.
        Parameters:
        c - a string collection

      • emptiesToNulls

        public static void emptiesToNulls​(Collection<String> c)
        Convert empty string entries to null.
        Parameters:
        c - a string collection

      • blanksToNulls

        public static void blanksToNulls​(Collection<String> c)
        Convert blank string entries to null.
        Parameters:
        c - a string collection