Generic Methods in java.util.Collections Class

Java Tutorials - Herong's Tutorial Examples - Version 7.03, by Dr. Herong Yang

Java Tutorials - Herong's Tutorial Examples

∟Generic Methods in java.util.Collections Class

This section provides my understandings of some generic methods defined in the java.util.Collections class.

From previous sections, we learned how to read generic method definitions. Now let's look at some generic methods defined in the java.util.Collections class and see if we understand their definitions.

<T> List<T> singletonList(T o) - Creates a List of T with an object of T. Parameterized type is used as the retunr type in this example.
<T> List<T> nCopies(int n, T o) - Creates a List of T with an object of T repeating it n times.
<T> Enumeration<T> enumeration(Collection<T> c) - Returns an Enumeration of T from the given Collection of T, Parameterized type is used as the method parameter this example.
<T> ArrayList<T> - list(Enumeration<T> e) - Converts an Enumeration of T to an ArrayList of T.
<T> boolean replaceAll(List<T> list, T oldVal, T newVal) - Finds and replaces an old object with a new object of T in a List of type T.
<T> void fill(List<? super T> list, T obj) - Fills a List of any supertype of T with an object of T. Wildcard parameterized type is used in this example.
<T> void copy(List<? super T> dest, List<? extends T> src) - Copies a List of any subtype of T to a List of supertype of T.
<T> List<T> emptyList() - Returns an empty List of T.
<T> int binarySearch(List<? extends Comparable<? super T>> list, T key) - Searches the "key" of type T in a List of any subtype of Comparable<? super T> and returns the index of "key". Nested wildcard parameterized type is used in this example.
<T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) - Returns the maximum element of the given collection, according to the natural ordering of its elements.
<T extends Comparable<? super T>> void sort(List<T> list) - Sorts the specified list into ascending order, according to the natural ordering of its elements.