Package com.norconex.commons.lang.collection

Class CollectionUtil

java.lang.Object
com.norconex.commons.lang.collection.CollectionUtil
public final class CollectionUtil extends Object
Collection-related utility methods.
Since:
2.0.0

  • Method Details

    • 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

      @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:

    • toStringList

      public static List<String> toStringList(Object... values)
      Converts a list of objects to an unmodifiable list of strings using default GenericConverter 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 an unmodifiable list of strings using default GenericConverter 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 an unmodifiable 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 an unmodifiable 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

    • unionList

      public static <T> List<T> unionList(Object... objects)
      Create a non-null mutable list containing the combination of supplied objects of the specified type. If the object is a Collection or array, it will be iterated over to populate the new list (recursively). Any null objects are ignored (not added to the returned list). Objects are returned in the order supplied.
      Parameters:
      objects - objects to combine into a new list
      Returns:
      a new non-null, mutable list
      Since:
      3.0.0

    • unionSet

      public static <T> Set<T> unionSet(Object... objects)
      Create a non-null mutable set containing the combination of supplied objects of the specified type (minus duplicates). If the object is a Collection or array, it will be iterated over to populate the new set (recursively). Any null objects are ignored (not added to the returned set). There are no guarantee on the order in which objects are returned.
      Parameters:
      objects - objects to combine into a new set
      Returns:
      a new non-null, mutable set
      Since:
      3.0.0