Java8 new features: Using lambda to process list collections

Java 8 is a new lambda expression that allows us to work with lists in simple, efficient code.

1. Traverse

 Public Static void Main (string[] args) {        List<User> userlist = Lists.newarraylist ();          New User (1L, "Zhang San",);         New User (2L, "John Doe", +);         New User (3L, "Harry", +);        Userlist.add (user1);        Userlist.add (user2);        Userlist.add (User3);         {            System.out.println (User.getname ());        });    

Operation Result:

2. List to map

  Public Static voidMain (string[] args) {List<User> userlist = Lists.newarraylist ();//storing Apple object collectionsUser user1=NewUser (1L, "Zhang San", 24); User User2=NewUser (2L, "John Doe", 27); User User3=NewUser (3L, "Harry", 21);        Userlist.add (user1);        Userlist.add (User2);        Userlist.add (USER3); //ID key, switch to mapMap<long,user> UserMap = Userlist.stream (). Collect (Collectors.tomap (User::getid, A, a, K1, K2),K1));    System.out.println (UserMap); }

Operation Result:

3. Group list: Object elements in list, grouped by an attribute

   Public Static voidMain (string[] args) {List<User> userlist = Lists.newarraylist ();//storing Apple object collectionsUser user1=NewUser (1L, "Zhang San", 24); User User2=NewUser (2L, "John Doe", 27); User User3=NewUser (3L, "Harry", 21); User User4=NewUser (4L, "Zhang San", 22); User User5=NewUser (5L, "John Doe", 20); User User6=NewUser (6L, "Harry", 28);        Userlist.add (user1);        Userlist.add (User2);        Userlist.add (USER3);        Userlist.add (USER4);        Userlist.add (USER5);        Userlist.add (USER6); //group UserList According to the namemap<string, list<user>> groupBy =Userlist.stream (). Collect (Collectors.groupingby (user::getname));    System.out.println (GroupBy); }

Operation Result:

4, Filter: Filter out the set of eligible elements

  Public Static voidMain (string[] args) {List<User> userlist = Lists.newarraylist ();//storing Apple object collectionsUser user1=NewUser (1L, "Zhang San", 24); User User2=NewUser (2L, "John Doe", 27); User User3=NewUser (3L, "Harry", 21); User User4=NewUser (4L, "Zhang San", 22); User User5=NewUser (5L, "John Doe", 20); User User6=NewUser (6L, "Harry", 28);        Userlist.add (user1);        Userlist.add (User2);        Userlist.add (USER3);        Userlist.add (USER4);        Userlist.add (USER5);        Userlist.add (USER6); //Remove the user named Zhang Sanlist<user> filterlist = Userlist.stream (). Filter (User-User.getname (). Equals ("Zhang San") . Collect (Collectors.tolist ()); Filterlist.stream (). ForEach (User-{System.out.println (User.getname ());    }); }

Operation Result:

5. Sum: Sums the data in the collection according to a property

  Public Static voidMain (string[] args) {List<User> userlist = Lists.newarraylist ();//storing Apple object collectionsUser user1=NewUser (1L, "Zhang San", 24); User User2=NewUser (2L, "John Doe", 27); User User3=NewUser (3L, "Harry", 21); User User4=NewUser (4L, "Zhang San", 22); User User5=NewUser (5L, "John Doe", 20); User User6=NewUser (6L, "Harry", 28);        Userlist.add (user1);        Userlist.add (User2);        Userlist.add (USER3);        Userlist.add (USER4);        Userlist.add (USER5);        Userlist.add (USER6); //Remove the user named Zhang San        intTotalage =Userlist.stream (). Maptoint (User::getage). sum (); System.out.println ("And:" +totalage); }

Operation Result:

Java8 new features: Using lambda to process list collections