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Java Collections class
Java collection class is used exclusively with static methods that operate on or return collections. It inherits Object class.
The important points about Java Collections class are:
- Java Collection class supports the polymorphic algorithms that operate on collections.
- Java Collection class throws a NullPointerException if the collections or class objects provided to them are null.
Collections class declaration
Let’s see the declaration for java.util.Collections class.
| SN | Modifier & Type | Methods | Descriptions |
|---|---|---|---|
| 1) | static <T> boolean | addAll() | It is used to adds all of the specified elements to the specified collection. |
| 2) | static <T> Queue<T> | asLifoQueue() | It returns a view of a Deque as a Last-in-first-out (LIFO) Queue. |
| 3) | static <T> int | binarySearch() | It searches the list for the specified object and returns their position in a sorted list. |
| 4) | static <E> Collection<E> | checkedCollection() | It is used to returns a dynamically typesafe view of the specified collection. |
| 5) | static <E> List<E> | checkedList() | It is used to returns a dynamically typesafe view of the specified list. |
| 6) | static <K,V> Map<K,V> | checkedMap() | It is used to returns a dynamically typesafe view of the specified map. |
| 7) | static <K,V> NavigableMap<K,V> | checkedNavigableMap() | It is used to returns a dynamically typesafe view of the specified navigable map. |
| 8) | static <E> NavigableSet<E> | checkedNavigableSet() | It is used to returns a dynamically typesafe view of the specified navigable set. |
| 9) | static <E> Queue<E> | checkedQueue() | It is used to returns a dynamically typesafe view of the specified queue. |
| 10) | static <E> Set<E> | checkedSet() | It is used to returns a dynamically typesafe view of the specified set. |
| 11) | static <K,V> SortedMap<K,V> | checkedSortedMap() | It is used to returns a dynamically typesafe view of the specified sorted map. |
| 12) | static <E> SortedSet<E> | checkedSortedSet() | It is used to returns a dynamically typesafe view of the specified sorted set. |
| 13) | static <T> void | copy() | It is used to copy all the elements from one list into another list. |
| 14) | static boolean | disjoint() | It returns true if the two specified collections have no elements in common. |
| 15) | static <T> Enumeration<T> | emptyEnumeration() | It is used to get an enumeration that has no elements. |
| 16) | static <T> Iterator<T> | emptyIterator() | It is used to get an Iterator that has no elements. |
| 17) | static <T> List<T> | emptyList() | It is used to get a List that has no elements. |
| 18) | static <T> ListIterator<T> | emptyListIterator() | It is used to get a List Iterator that has no elements. |
| 19) | static <K,V> Map<K,V> | emptyMap() | It returns an empty map which is immutable. |
| 20) | static <K,V> NavigableMap<K,V> | emptyNavigableMap() | It returns an empty navigable map which is immutable. |
| 21) | static <E> NavigableSet<E> | emptyNavigableSet() | It is used to get an empty navigable set which is immutable in nature. |
| 22) | static <T> Set<T> | emptySet() | It is used to get the set that has no elements. |
| 23) | static <K,V> SortedMap<K,V> | emptySortedMap() | It returns an empty sorted map which is immutable. |
| 24) | static <E> SortedSet<E> | emptySortedSet() | It is used to get the sorted set that has no elements. |
| 25) | static <T> Enumeration<T> | enumeration() | It is used to get the enumeration over the specified collection. |
| 26) | static <T> void | fill() | It is used to replace all of the elements of the specified list with the specified elements. |
| 27) | static int | frequency() | It is used to get the number of elements in the specified collection equal to the specified object. |
| 28) | static int | indexOfSubList() | It is used to get the starting position of the first occurrence of the specified target list within the specified source list. It returns -1 if there is no such occurrence in the specified list. |
| 29) | static int | lastIndexOfSubList() | It is used to get the starting position of the last occurrence of the specified target list within the specified source list. It returns -1 if there is no such occurrence in the specified list. |
| 30) | static <T> ArrayList<T> | list() | It is used to get an array list containing the elements returned by the specified enumeration in the order in which they are returned by the enumeration. |
| 31) | static <T extends Object & Comparable<? super T>> T | max() | It is used to get the maximum value of the given collection, according to the natural ordering of its elements. |
| 32) | static <T extends Object & Comparable<? super T>> T | min() | It is used to get the minimum value of the given collection, according to the natural ordering of its elements. |
| 33) | static <T> List<T> | nCopies() | It is used to get an immutable list consisting of n copies of the specified object. |
| 34) | static <E> Set<E> | newSetFromMap() | It is used to return a set backed by the specified map. |
| 35) | static <T> boolean | replaceAll() | It is used to replace all occurrences of one specified value in a list with the other specified value. |
| 36) | static void | reverse() | It is used to reverse the order of the elements in the specified list. |
| 37) | static <T> Comparator<T> | reverseOrder() | It is used to get the comparator that imposes the reverse of the natural ordering on a collection of objects which implement the Comparable interface. |
| 38) | static void | rotate() | It is used to rotate the elements in the specified list by a given distance. |
| 39) | static void | shuffle() | It is used to randomly reorders the specified list elements using a default randomness. |
| 40) | static <T> Set<T> | singleton() | It is used to get an immutable set which contains only the specified object. |
| 41) | static <T> List<T> | singletonList() | It is used to get an immutable list which contains only the specified object. |
| 42) | static <K,V> Map<K,V> | singletonMap() | It is used to get an immutable map, mapping only the specified key to the specified value. |
| 43) | static <T extends Comparable<? super T>>void | sort() | It is used to sort the elements presents in the specified list of collection in ascending order. |
| 44) | static void | swap() | It is used to swap the elements at the specified positions in the specified list. |
| 45) | static <T> Collection<T> | synchronizedCollection() | It is used to get a synchronized (thread-safe) collection backed by the specified collection. |
| 46) | static <T> List<T> | synchronizedList() | It is used to get a synchronized (thread-safe) collection backed by the specified list. |
| 47) | static <K,V> Map<K,V> | synchronizedMap() | It is used to get a synchronized (thread-safe) map backed by the specified map. |
| 48) | static <K,V> NavigableMap<K,V> | synchronizedNavigableMap() | It is used to get a synchronized (thread-safe) navigable map backed by the specified navigable map. |
| 49) | static <T> NavigableSet<T> | synchronizedNavigableSet() | It is used to get a synchronized (thread-safe) navigable set backed by the specified navigable set. |
| 50) | static <T> Set<T> | synchronizedSet() | It is used to get a synchronized (thread-safe) set backed by the specified set. |
| 51) | static <K,V> SortedMap<K,V> | synchronizedSortedMap() | It is used to get a synchronized (thread-safe) sorted map backed by the specified sorted map. |
| 52) | static <T> SortedSet<T> | synchronizedSortedSet() | It is used to get a synchronized (thread-safe) sorted set backed by the specified sorted set. |
| 53) | static <T> Collection<T> | unmodifiableCollection() | It is used to get an unmodifiable view of the specified collection. |
| 54) | static <T> List<T> | unmodifiableList() | It is used to get an unmodifiable view of the specified list. |
| 55) | static <K,V> Map<K,V> | unmodifiableMap() | It is used to get an unmodifiable view of the specified map. |
| 56) | static <K,V> NavigableMap<K,V> | unmodifiableNavigableMap() | It is used to get an unmodifiable view of the specified navigable map. |
| 57) | static <T> NavigableSet<T> | unmodifiableNavigableSet() | It is used to get an unmodifiable view of the specified navigable set. |
| 58) | static <T> Set<T> | unmodifiableSet() | It is used to get an unmodifiable view of the specified set. |
| 59) | static <K,V> SortedMap<K,V> | unmodifiableSortedMap() | It is used to get an unmodifiable view of the specified sorted map. |
| 60 | static <T> SortedSet<T> | unmodifiableSortedSet() | It is used to get an unmodifiable view of the specified sorted set. |
Java Collections Example
Output:
Initial collection value:[C, Core Java, Advance Java] After adding elements collection value:[C, Core Java, Advance Java, Servlet, JSP] After adding array collection value:[C, Core Java, Advance Java, Servlet, JSP, C#, .Net]
Java Collections Example: max()
Output:
Value of maximum element from the collection: 67
Java Collections Example: min()
Output:
Value of minimum element from the collection: 8
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