Java learns from zero 24 points (Collection tool class collections)

I. Collections introduction in the application development of the collection, several interfaces and several subclasses of the set are the most commonly used, but a set of tool class--collections is provided in the JDK, which can be set up directly by this kind of convenient operation.common methods and constants of collections class

No.	Method	Type	Describe
1	public static final List empty_list	Constant	Returns an empty list collection
2	public static final Set Empty_set	Constant	Returns an empty set collection
3	public static final Map Empty_map	Constant	Returns an empty map collection
4	public static <T> Boolean addall (collection<? super t> C, T ... a)	Ordinary	Add content to a collection
5	public static <t extends Object & comparable<? Super t>> T Max (collection<? extends t> Coll)	Ordinary	Find the largest content, sort by comparer returns the largest element of a given set based on the natural order of the elements
6	public static <t extends Object & comparable<? Super t>> T min (collection<? extends t> Coll)	Ordinary	Finds the smallest content in the collection, sorted by comparer returns the smallest element of a given set based on the natural order of the elements
7	public static <T> Boolean replaceall (list<t> list,t oldval,t newval)	Ordinary	Replaces the specified contents of a collection with new content replaces all occurrences of a specified value in the collection with another value
8	public static void reverse (list<?> List)	Ordinary	Reverses the order of the elements in the specified list collection.
9	public static <T> int BinarySearch (list<? extends Comparable<? Super t>> List,t Key)	Ordinary	Finds the specified content in the collection Finds the specified list collection using the binary lookup algorithm to obtain a reference to the The index position of the fixed object.
10	public static final <T> list<t> emptylist ()	Ordinary	Returns an empty list collection
11	public static final <K,V> map<k,v> Emptymap ()	Ordinary	Returns an empty map collection
12	public static final <T> set<t> Emptyset ()	Ordinary	Returns an empty set collection
13	public static <t extends Comparable<? Super t>> void Sort (list<t> List)	Ordinary	Set sort operation, sorted according to comparable interface The specified list collection is ascending according to the natural order of the elements The order is ordered.
14	public static void Swap (list<?> list,int i,int J)	Ordinary	Swaps an element at a specified position

Invert the order of elements in the specified list collection

 PackageCom.pb.demo2;Importjava.util.Collections;Importjava.util.LinkedList;Importjava.util.List; Public classCollectionsTest1 { Public Static voidMain (string[] args) {//declaring a collection and adding elementslinkedlist<string> list =NewLinkedlist<string>(); List.add ("One"); List.add ("Both"); List.add ("Three"); System.out.println ("======= Normal traversal ============");  for(String s:list) {System.out.print (s+ "\ T");        } System.out.println (); System.out.println ("======= Execution Reverse method ============");        Collections.reverse (list);  for(String s:list) {System.out.print (s+ "\ T"); }    }}

The function of the sort method is to sort the specified list collection in ascending order

 PackageCom.pb.demo2;Importjava.util.ArrayList;Importjava.util.Collections;Importjava.util.List; Public classCollectionsTest2 { Public Static voidMain (string[] args) {//declaring collections and adding setslist<integer> list =NewArraylist<integer>(); List.add (7); List.add (2); List.add (5); List.add (3); List.add (1); System.out.println ("======= Normal traversal ============");  for(Integer i:list) {System.out.print (i+ "\ T"); } System.out.println ("\n======= performs the Sort method ============");        Collections.sort (list);  for(Integer i:list) {System.out.print (i+ "\ T"); } System.out.println ("\n======= Execution Reverse method ============");        Collections.reverse (list);  for(Integer i:list) {System.out.print (i+ "\ T"); }    }}

Results:

======= Normal traversal ============7    2    5    3    1    ======= Perform sort method ============1    2    3    5    7    ======= Execute Reverse method ============7    5    3    2    1    

V. Methods for finding and replacing collections

 PackageCom.pb.demo2;Importjava.util.ArrayList;Importjava.util.Collections;Importjava.util.List; Public classCollectionsTest3 { Public Static voidMain (string[] args) {//declaring collections and adding sets//Create a collectionlist<string> list =NewArraylist<string>(); //10 + different words addedList.add ("This"); List.add ("Is"); List.add ("Collection"); List.add ("Test"); List.add ("and"); List.add ("We"); List.add ("Can"); List.add ("Learn"); List.add ("How"); List.add ("To"); System.out.println ("======= Normal traversal ============");  for(String s:list) {System.out.print (s+ "\ T"); }        //prints the largest and smallest elements in the output collectionSystem.out.println ("\n======== Maximum and minimum elements ========= in the print output collection"); String Max=Collections.max (list); String min=collections.min (list); System.out.println ("Maximum value in the list collection:" +max); System.out.println ("Minimum value in the list collection:" +min); System.out.println ("\n======= performs the Sort method ============");        Collections.sort (list);  for(String s:list) {System.out.print (s+ "\ T"); }        //BinarySearch is used if you want to sort before you can use theSystem.out.println ("\n=============binarysearch find index ================ based on content"); System.out.println ("We index in list is:" +collections.binarysearch (List, "we"))); System.out.println ("=============replaceall Method ================"); //ReplaceAllCollections.replaceall (List, "we", "our");  for(String s:list) {System.out.print (s+ "\ T"); }        //SwapSystem.out.println ("======swap========"); Collections.swap (list,0, 9);  for(String s:list) {System.out.print (s+ "\ T"); }                }}

Results:

======= Normal traverse ============This is    collection    test    and    we    can    learn    How to ======== the largest and smallest elements in the print output collection ========= The maximum value in the list collection: The minimum value in the Welist collection: and ======= Perform the sort method     ============and    can collection how are    learn    test    this To     we    =============binarysearch search index based on content ================We index in list is:9=== ==========replaceall method ================and    can    collection how is    learn    test      This    To    our    ======swap======== We can collection how are    Learn    test      This    To and        

Vi. Generating Collections using Arrays.aslist

 PackageCom.pb.demo2;Importjava.util.Arrays;Importjava.util.List; Public classTest1 { Public Static voidMain (string[] args) {String str= "A,b,c,d,e,f"; List<String> list1=arrays.aslist (str); System.out.println ("Length of List1:" +list1.size ());  for(String s:list1) {System.out.print (s+ "\ T"); } System.out.println ("\ nthe collection is separated by commas"); List<String> list2=arrays.aslist (Str.split (",")); System.out.println ("Length of List2:" +list2.size ());  for(String s:list2) {System.out.print (s+ "\ T"); }    }}

Results:

Length of List1:  1a,b,c,d,e,f The    length of the collection List2 when separated by commas  :6a    b    c    d    e    f    

Java learns from zero 24 points (Collection tool class collections)