Java Learning Lesson 43rd-Collection Framework Tools class (I)

Collections: A tool class for the collection framework

The methods are static.

Sorting Method Demo

Import Java.util.arraylist;import java.util.collections;import Java.util.comparator;import Java.util.List;class Comparabyleng implements Comparator<string>{public int Compare (string O1, string o2) {int t = o1.length ()-O2.lengt h (); return T==0?o1.compareto (O2): t; }}public class Main {public static void Main (string[] args) {Colletyions_demo ();}    public static void Colletyions_demo () {list<string> li = new arraylist<string> (); Li.add ("ASD");  Li.add ("D"); Li.add ("efasd"); Li.add ("EFASD"); Li.add ("DSSSFD"); Li.add ("Xxxxd");//system.out.println (list);//collections.sort (list);//Sort//system.out.println (list);//sort: public static <t extends Comparable<? Super t>> void Sort (list<t> list)//analog sort//mysort (list);//system.out.println (list); Mysort (Li,new Comparabyleng ()); System.out.println (LI); Collections.sort (Li,new Comparabyleng ()); System.out.println (LI);} /*public static <t extends Comparable<? Super t>> void Mysort (list<t> List) {for (int i = 0; I < List.size ()-1; i++) {for (int j = i+1, J < List.size (); j + +) {if (List.get (i). CompareTo (List.get (j)) >0) {Collections.swap (list, I, J) ;//Tool class Exchange}}}}*/public static <T> void Mysort (list<t> li,comparator<? Super t> com) {for (int i = 0; I & Lt Li.size ()-1; i++) {for (int j = i+1, J < Li.size (); j + +) {if (Com.compare (Li.get (i), Li.get (j)) > 0) {collections.swap (Li, I, J) ;}}}}}

Two-point lookup, the best value method demo

Import Java.util.arraylist;import java.util.collections;import Java.util.comparator;import java.util.List;public Class Main {public static void Main (string[] args) {Colletyions_demo ();} public static void Colletyions_demo () {list<string> li = new arraylist<string> (); Li.add ("ASD");    Li.add ("D"); Li.add ("efasd");  Li.add ("EFASD"); Li.add ("DSSSFD"); Li.add ("Xxxxd"); Collections.sort (LI); System.out.println (li); int index = Collections.binarysearch (LI, "D"); SYSTEM.OUT.PRINTLN (index);//negative indicates not found//gets maximum value string maxstrstring = Collections.max (LI); System.out.println ("max =" +maxstrstring);//Gets the minimum value string minstrstring = Collections.min (LI); System.out.println ("min =" +minstrstring);//Take the longest string maxlenstring = Collections.max (li,new Comparabyleng ()); System.out.println (maxlenstring);}}

reversal, replacement method demo

Import Java.util.arraylist;import java.util.collections;import Java.util.list;import Java.util.TreeSet;public class Main {public static void main (string[] args) {Colletyions_demo ();} public static void Colletyions_demo () {//principle//treeset<string> ts = new treeset<string> (New comparator< String> () {//public int compare (string O1, String O2) {////return o2.compareto (O1);//}//});//Package treeset<string > ts = new treeset<string> (Collections.reverseorder ()), Ts.add ("ad"), Ts.add ("Xad"); Ts.add ("FDAGRRGD"); Ts.add ("a"); Ts.add ("Gedsad"); SYSTEM.OUT.PRINTLN (TS);//If there is a comparator, reversal//length reversal treeset<string> td = New Treeset<string> ( Collections.reverseorder (New Comparabyleng ())), Td.add ("ad"), Td.add ("Xad"); Td.add ("FDAGRRGD"); Td.add ("a"); Td.add ("Gedsad"); SYSTEM.OUT.PRINTLN (TD);//replaceall/reverse method List<string> al = new arraylist<string> (); Al.add ("ads"); Al.add ("DS"); Al.add ("s"); Collections.reverse (AL); System.out.println (AL); Collections.replaceall (AL, "s", "Y");//actually-&GT Set (IndexOf ("s"), "Y") System.out.println (AL);}}

Other methods
1、fill(List<? super T> list, T obj)
Replaces all elements in the specified list with the specified element.

Collections.fill (list, "ASD");

2、shuffle(List<?> list)
To displace a specified list using the default random source

Collections.shuffle (list); random

More ways to look at API documentation ...

To convert a non-synchronous collection to a synchronous collection

static <T> Collection<T>	synchronizedCollection(Collection<T> c) Returns the synchronization (thread-safe) collection that the specified collection supports.
static <T> List<T>	synchronizedList(List<T> list) Returns a list of synchronized (thread-safe) support for the specified list.
static <K,V> Map<K,V>	synchronizedMap(Map<K,V> m) Returns the synchronized (thread-safe) mappings supported by the specified mappings.
stat IC <T> set<t> synchronizedset (set<t> s) Returns the synchronous (thread-safe) set supported by the specified set.
stat IC <K,V> sortedmap<k,v>	synchronizedsortedmap (sortedmap<k,v> m) Returns a synchronous (thread-safe) ordered map supported by the specified ordered map.
static <T> SortedSet<T>	synchronizedSortedSet(SortedSet<T> s) Returns a synchronous (thread-safe) ordered set supported by the specified ordered set.

Conversion principle:

List List = new ArrayList (); List = Mycollections.synlist (list);//Returns a synchronized ListClass mycollections{public list synlist (List list) {return new MyList ( list);} Private class MyList implements List{private List list;private static Final Object lock = new Object ();p ublic MyList () {su per ();//TODO auto-generated constructor stub}public MyList (List list) {super (); this.list = List;} Public boolean Add (Object obj) {synchronized (lock) {return list.add (obj);}} public boolean remove (Object obj) {synchronized (lock) {return list.remove (obj);}}}

Java Learning Lesson 43rd-Collection Framework Tools class (I)