Java list< object > Goto Set, Map (Advanced)

 Packagecom.demo.entity; Public classBook {Private intID; PrivateString name;  PublicBook () {} PublicBook (intID, String name) {         This. ID =ID;  This. Name =name; }     Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; } @Override PublicString toString () {return"book{" + "id=" + ID + ", name= '" + name + ' \ ' + '} '; }}

Main

 PackageCom.demo;ImportCom.demo.entity.Book;ImportJava.util.*;Importjava.util.stream.Collectors; Public classMain {Private StaticList<string> SimpleList =NewArraylist<>(); Private StaticList<book> normallist =NewArraylist<>(); Static{Simplelist.add ("Apple"); Simplelist.add ("Apple"); Simplelist.add ("Banana"); Simplelist.add ("Orange"); Normallist.add (NewBook (1, "Apple")); Normallist.add (NewBook (2, "Banana")); Normallist.add (NewBook (3, "Orange")); Normallist.add (NewBook (4, "Pig")); }     Public Static voidMain (string[] args) {System.out.println ("----------------Simple List---------------"); Simplelist.foreach (eSystem.out.println (e)); System.out.println ("----------------simple list turn set---------------"); Set<String> Simpleset =NewHashset<>(SimpleList); Simpleset.foreach (e-System.out.println (e)); System.out.println ("----------------General List---------------"); Normallist.foreach (e-System.out.println (e)); System.out.println ("----------------normal list to set---------------"); Set<String> Normalset =Normallist.stream (). Map (Book::getname). Collect (Collectors.toset ()); Normalset.foreach (e-System.out.println (e)); System.out.println ("----------------normal list to list---------------"); List<Integer> list =Normallist.stream (). Map (Book::getid). Collect (Collectors.tolist ()); List.foreach (e-System.out.println (e)); System.out.println ("----------------normal list to map---------------"); Map<Integer,Book> Normalmap = Normallist.stream (). Collect (Collectors.tomap (Book::getid, (b)b)); Normalmap.foreach (ID, book)-{System.out.println (id+ "::" +Book );    }); }}

Run results

----------------Simple List---------------appleapplebananaorange----------------Simple list turn set---------------bananaorangeapple---- ------------General List---------------book{id=1, name= ' Apple '}book{id=2, name= ' Banana '}book{id=3, name= ' Orange '}book{ id=4, name= ' Pig '}---------------- Normal list to set---------------Appleorangebananapig----------------General List---------------1234----------------General list to map---- -----------1::book{id=1, name= ' Apple '}2::book{id=2, name= ' Banana '}3::book{id=3, name= ' Orange '}4::book{id=4, Name= ' Pig '}

Java list< object > Goto Set, Map (Advanced)