List、Collections

List, Set Description

• java.util.ArrayList set of stored data structure is an array structure. Elemental additions and deletions slow, fast lookup
• java.util.LinkedList data storage structure is a set of linked list structure. Convenient element to add, delete collections
• java.util.LinkedHashSet, it is a data storage structure list and hash table combination. Ordered
• java.util.HashSet is an implementation of the Set interface, its stored element is not repeatable, and (i.e., inconsistent access sequence) elements are disordered. Java.util.HashSet achieve the underlying fact is supported by a java.util.HashMap

Collentions Tools

method:

• public static <T> boolean addAll (Collection <T> c, T ... elements): add some elements to the collection.
• public static void shuffle (<?> List list) out of order: disrupt the order of collection.
• public static <T> void sort (List <T> list): The elements in the set according to the default ordering rules.
• public static <T> void sort (List <T> list, Comparator <super T?>): The elements in the collection sorted according to the specified rules.

addAll Case:

private static void addAll() {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(1);
        list.add(2);
        list.add(3);
        System.out.println("list1"+list);
        Collections.addAll(list, 4, 5, 6);
        System.out.println("list2"+list);
    }
//list1[1, 2, 3]
//list2[1, 2, 3, 4, 5, 6]

Sort function:

   / ** 
     * get the first character in descending order 
     * / 
    Private  static  void collecyionsSort () { 
        the ArrayList <String> List = new new the ArrayList <> (); 
        Collections.addAll (List, "ha", "weeping" "hee" ); 
        the Collections.sort (List, new new Comparator <String> () { 
            @Override 
            public  int Compare (String O1, O2 String) {
                 return o2.charAt (0) -o1.charAt (0 ); 
            } 
        }); 
        System.out.println ( "List =" + List);
    }
// list = [hee, weeping, ha ha]