Map of Guava Learning

Guava Chinese is the meaning of pomegranate, this project is an open source project of Google, contains many Google Core Java Common library.

Currently mainly includes:

• Com.google.common.annotations
• Com.google.common.base
• Com.google.common.collect
• Com.google.common.io
• Com.google.common.net
• Com.google.common.primitives
• Com.google.common.util.concurrent
  Online API Doc:http://tool.oschina.net/apidocs/apidoc?api=guava

The following person classes are available:

 Public  class  person {    PrivateString name;Private intAge Public  Person(String name,intAge) { This. name = name; This. Age = Age; } PublicStringGetName() {returnName } Public int Getage() {returnAge }@Override     PublicStringtoString() {return "person{"+"Name= '"+ name +' \ '+", age="+ Age +'} '; }}

1 A unique key after converting list to Map1.1 conversion

 Public  class testmap {     Public Static void Main(String args[]) {list<person> persons = Arrays.aslist (NewPerson ("Zhang", the),NewPerson ("Wang", -),NewPerson ("Lee", -)        );/** * The converted map has a unique key * /map<string, person> map = maps.uniqueindex (persons,NewFunction<person, string> () {@Override             PublicStringApply(Person person) {returnPerson.getname ();    }        }); }}

1.2 The converted key is not unique

 Public  class testmap {     Public Static void Main(String args[]) {list<person> persons = Lists.newarraylist (NewPerson ("Zhang", the),NewPerson ("Zhang", -),NewPerson ("Lee", -)        );/** * The converted map has duplicate keys */multimap<string, person> Multimap = multimaps.index (persons,NewFunction<person, string> () { PublicStringApply(Person person) {returnPerson.getname ();    }        }); }}

2 Convert set to map

 Public  class testmap {     Public Static void Main(String args[]) {set<person> persons = Sets.newhashset (NewPerson ("Zhang", the),NewPerson ("Zhang", -),NewPerson ("Lee", -)        );/** * The value of set is key to calculate a value * /Map<person, string> map = maps.asmap (persons,NewFunction<person, string> () { PublicStringApply(Person person) {returnPerson.getname ();    }        }); }}

3 Convert the value of map

 Public  class testmap {     Public Static void Main(String args[]) {list<person> persons = Lists.newarraylist (NewPerson ("Zhang", the),NewPerson ("Wang", the),NewPerson ("Lee", -)        ); map<string, person> map = maps.uniqueindex (persons,NewFunction<person, string> () { PublicStringApply(Person person) {returnPerson.getname (); }        });/** * Use key and value as input to calculate a new value */map<string, integer> map2 = maps.transformentries (map,NewMaps.entrytransformer<string, Person, integer> () {@Override             PublicIntegerTransformentry(String s, person person) {returnPerson.getage (); }        });/** * Use function to calculate a new value */map<string, double> map3 = maps.transformvalues (map,NewFunction<person, double> () {@Override             PublicDoubleApply(Person person) {return(Double) Person.getage ();    }        }); }}

4 Filter the map to match the criteria in the map

 Public  class testmap {     Public Static void Main(String args[]) {list<person> persons = Lists.newarraylist (NewPerson ("Zhang", the),NewPerson ("Wang", the),NewPerson ("Lee", -)        ); map<string, person> map = maps.uniqueindex (persons,NewFunction<person, string> () { PublicStringApply(Person person) {returnPerson.getname ();        }        }); Map = maps.filterentries (map,NewPredicate<map.entry<string, person>> () {@Override             Public Boolean Apply(map.entry<string, person> stringpersonentry) {returnStringpersonentry.getkey ()! =NULL&& stringpersonentry.getvalue ()! =NULL;        }        }); Map = Maps.filterkeys (map,NewPredicate<string> () {@Override             Public Boolean Apply(String s) {returns! =NULL&& s.length () >2;        }        }); Map = maps.filtervalues (map,NewPredicate<person> () {@Override             Public Boolean Apply(Person person) {returnPerson! =NULL&& person.getage () > the; }        }); for(Map.entry<string, Person> entry:map.entrySet ()) {System.out.println (Entry.getkey () +" "+ Entry.getvalue ()); }    }}

Map of Guava Learning