JAVA8-Functional programming

1. What is functional programming?

At the heart of functional programming is the use of immutable values and functions when thinking about problems, and functions that process a value and map it to another value.

2. Lambda expression Learning

Important: A lambda expression is an anonymous method that passes behavior like data, and the common structure is as follows:binaryoperator<integer> add = (x, y)->x+y.

3. Flow: Common flow operations

3.1, Collect (ToList ())

// Early Evaluation Method long count = Artists.stream (). Filter (A->a.isfrom ("China"long count2 = Artists.stream () . Filter (B->b.getname (). Equals ("TTG"long count3 = artists.stream ()      . Filter (A- >{     System.out.println (A.getname ());      return a.isfrom ("China");      })      . Count ();

List<string> collected = Stream.of ("A", "B", "C"= jsonarray.tojsonstring (collected); boolean isequal = Collected.equals (Arrays.aslist ("A", "B", "C"));

3.2. Map

        // 2.map        list<string> str = stream.of ("A", "B", "C")                , s.touppercase ())                . Collect ( Collectors.tolist ());         = jsonarray.tojsonstring (str);         boolean issame = Realstr.equals (Arrays.aslist ("A", "B", "C"));

3.3. Filter

        // 3.filter        List<object> str2 = Stream.of ("abc", "1abc", "ABC1")                , Isdight (S.charat (0)))                . Collect (Collectors.tolist ());         = Jsonarray.tojsonstring (STR2);

3.4, FlatMap

// The Flatmap:flatmap method can replace a value with a stream and then concatenate multiple streams into a stream List<string> STR3 = Stream.of (Arrays.aslist ("A", "B", "C"), Arrays.aslist ("D", "E"))                  Stringlist.stream ())                . Collect (Collectors.tolist ());   = Jsonarray.tojsonstring (STR3);

3.5, Max and Min

// Max min list<track> tracks = Arrays.aslist ( "Bakai", 524),    new track ("Violets For Your Furs ", 378),    new track (" Time Is ", 451=                 tracks.stream (). Min ( Comparator.comparing (track >track.getlength ()))    . get ();

3.6. Integration + General mode

  //Reduce//1. Accumulation        intCOUNT4 = Stream.of). Reduce (0, (acc,res)->acc+res); //IntegrationAlbum Album =NULL; Set<String> Orgin =Album.getmusicians (). Filter (ArtistArtist.getname (). StartsWith ("the"). Map (artist-artist.getnationality ()). Collect (Collectors.toset ());        System.out.println (COUNT4); intTotalmembers = 0;  for(Artist artist:artists) {Stream<Artist> Members =artist.getmembers (); Totalmembers+=Members.count (); }    }

JAVA8-Functional programming