Java Collection Framework 03

Use of the Collections tool class

 Public classNewsImplementsComparable {Private intId//News Number    PrivateString title;//News Headlines@Override PublicString toString () {return"News [number =" + ID + ", title =" + title + "]"; }         PublicNews () {//non-parametric construction        Super(); }     PublicNews (intID, String title) {//with parametric construction        Super();  This. ID =ID;  This. title =title; }     Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetTitle () {returntitle; }     Public voidSettitle (String title) { This. title =title; }    //override sorted rule ascending@Override Public intcompareTo (Object o) {News news=(News) o; if(News.getid () = = This. ID) {            return0; }Else if(News.getid () < This. ID) {            return1;//descending return-1;}Else {            return-1;//descending return 1;        }    }}

To create a test class

 Public classCollectionstest { Public Static voidMain (string[] args) {/** Tool class for operation set collections **/        //Create a collectionList<string> list=NewArraylist<string>(); List.add ("B"); List.add ("D"); List.add (C); List.add (A); System.out.println ("no sort = =" +list);//Order of insertion time//to randomly sort a collectioncollections.shuffle (list); //Draw number 136 order must be 631 wrongSystem.out.println ("random sort = = =" +)list); //in ascending order of lettersCollections.sort (list); System.out.println ("Ascending = =" +list); //descending also must be after ascendingcollections.reverse (list); System.out.println ("Descending = =" +list); //The position of the query "B" in the collection must be sorted in ascending order before queryingCollections.sort (list); System.out.println (Collections.binarysearch (list,A)); System.out.println ("****************************"); List<News> news=NewArraylist<news> ();//want to implement the sorting of objectsNews.add (NewNews (3, "News 3")); News.add (NewNews (1, "News 1")); News.add (NewNews (4, "News 4")); News.add (NewNews (2, "News 2"));  for(News news2:news) {System.out.println (NEWS2); }        /** If news does not rewrite the comparable interface in the CompareTo () is compiled error! * We must rewrite CompareTo () to define the rules*/Collections.sort (News); System.out.println ("After the object is sorted ...");  for(News news2:news) {System.out.println (NEWS2); }} @Test Public  voidtest1 () {//Convert a string to a string array by using split () in the String classString[] str1= "A b c D D d". Split (""); //convert an array to a collectionList<string> aslist =arrays.aslist (STR1);        System.out.println (aslist); String[] str2= "C D". Split (""); List<String> aslist2=arrays.aslist (STR2); //last occurrence of positionSystem.out.println (Collections.lastindexofsublist (Aslist, asList2)); //first occurrence of positionSystem.out.println (Collections.indexofsublist (Aslist, asList2)); } @Test Public  voidtest2 () {string[] str1= "A b c D E F". Split (""); //convert an array to a collectionlist<string> list =arrays.aslist (STR1);        SYSTEM.OUT.PRINTLN (list); //the elements in the collection move backward distance a position, and then the overridden element loops forwardCollections.rotate (list, 2);    SYSTEM.OUT.PRINTLN (list); }}

Efficiency comparison of 3.MAP traversal

@Test Public  voidTest () {Map<string, object> map=NewHashmap<string, object>();  for(inti = 0; I <1000000; i++) {Map.put ("Key" +i, "value" +i); }       //gets the current number of millisecondsLong a=System.currenttimemillis (); //traverse map to get a collection of all keys firstSet<string> set =Map.keyset ();  for(String key:set) {map.get (key);//get value based on key       }       //gets the current number of millisecondsLong b=System.currenttimemillis (); System.out.println ("The time to traverse with keyset is:" + (B-a)); //use entry to traverse the most efficientset<entry<string, object>> entryset =Map.entryset ();  for(Entry<string, object>Entry:entryset)      {Entry.getvalue (); }      //gets the current number of millisecondsLong c=System.currenttimemillis (); System.out.println ("The time to traverse with EntrySet is:" + (C-b));}

The sorting of Chinese characters

 Public classListtest { Public Static voidMain (string[] args) {//implement the ordering of all Chinese characters into a language environmentComparator<object> collator=collator.getinstance (Locale.china); ArrayList<String> list=NewArraylist<string>(); List.add (Hello); List.add (Good); List.add ("Ah"); List.add ("It's good"); //Tool Classcollections.sort (list, collator);  for(String string:list) {System.out.println (string); }    }}

Java Collection Framework 03