Java Learning--collections Collection Tool class use

* Tool classes for operating collection and map: Collections

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* Reverse (List): Reverses the order of the elements in the list
Shuffle (list): Randomly sort the elements of a List collection
Sort (list): Sorts the specified List collection elements in ascending order based on the natural ordering of the elements
Sort (list,comparator): Sorts the List collection elements according to the order in which the specified Comparator is produced
Swap (list,int, int): Swaps the I and J elements in the specified list collection

1 @Test2      Public voidtestCollections1 () {3List List =NewArrayList ();4List.add (123);5List.add (456);6List.add (12);7List.add (78);8 System.out.println (list);9 collections.reverse (list);Ten System.out.println (list); One collections.shuffle (list); A System.out.println (list); - Collections.sort (list); - System.out.println (list); theCollections.swap (list, 0, 2); - System.out.println (list); -}

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* Objectmax (Collection): Returns the largest element in a given set based on the natural order of the element
Objectmax (Collection,comparator): Returns the largest element in a given set, based on the order specified by Comparator
Objectmin (Collection)
Objectmin (Collection,comparator)
Intfrequency (Collection,object): Returns the number of occurrences of the specified element in the specified collection
Voidcopy (List dest,list src): Copy content from SRC to dest
Booleanreplaceall (list list,object oldval,object newval): Replaces all old values of the List object with the new value

1 @Test2      Public voidTestCollections2 () {3List List =NewArrayList ();4List.add (123);5List.add (456);6List.add (12);7List.add (78);8List.add (456);9Object obj =Collections.max (list);Ten System.out.println (obj); One         intCount = collections.frequency (list, 4567); A System.out.println (count); -         //implementing the copy of List -         //List list1 = new ArrayList ();//How to implement the error theList List1 = Arrays.aslist (Newobject[list.size ()]); - collections.copy (List1, list); - System.out.println (list1); -         //The list's thread safety is ensured by the following methods.  +List List2 =collections.synchronizedlist (list); - System.out.println (list2); +}

Java Learning--collections Collection Tool class use