"Multithreading" lets a thread return a value

Many times, we use threads to handle some business and want to get results, when we can use callable.

The following example simulates using a thread query db to get a list.

Example

Thread that returns a list data

 Packagecom.nicchagil.study.thread.cnblogs.No02 A thread that can return a value;Importjava.util.ArrayList;ImportJava.util.HashMap;Importjava.util.List;ImportJava.util.Map;Importjava.util.concurrent.Callable;ImportJava.util.concurrent.TimeUnit; Public classQuerydatathreadImplementsCallable<list<map<string, object>>> {        Privatemap<string, object> param =NULL;  PublicQuerydatathread (map<string, object>param) {        Super();  This. param =param; } @Override PublicList<map<string, object>> call ()throwsException {/*get result set after simulating query db*/System.out.println ("Param" +param); Map<string, object> map1 =NewHashmap<string, object>(); Map1.put ("id", "1001"); Map1.put ("Name", "Nick Huang."); Map<string, object> map2 =NewHashmap<string, object>(); Map2.put ("id", "1002"); Map2.put ("Name", "Darren Lin"); List<map<string, object>> list =NewArraylist<map<string, object>>();        List.add (MAP1);                List.add (MAP2); /*set a short sleep to see the effect*/        Try{TimeUnit.SECONDS.sleep (3); } Catch(interruptedexception e) {e.printstacktrace (); }                returnlist; }    }

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Starts the thread and waits for the result to be returned

 Packagecom.nicchagil.study.thread.cnblogs.No02 A thread that can return a value;ImportJava.util.HashMap;Importjava.util.List;ImportJava.util.Map;Importjava.util.concurrent.ExecutionException;ImportJava.util.concurrent.ExecutorService;Importjava.util.concurrent.Executors;Importjava.util.concurrent.Future; Public classCall { Public Static voidMain (string[] args) {List<map<string, object>> list =NULL; Try{List=query (); } Catch(Exception e) {//TODO auto-generated Catch blockE.printstacktrace (); }                if(List! =NULL&& list.size () > 0) {             for(Map<string, object>map:list) {System.out.println ("ID:" + map.get ("id") + ", Name:" + map.get ("name"))); }        }    }        /*** Business methods for simulating queries*/     Public Staticlist<map<string, object>> query ()throwsinterruptedexception, executionexception {executorservice es=Executors.newcachedthreadpool (); /*simulating query Parameters*/Map<string, object> param =NewHashmap<string, object>(); Param.put ("username", "Derick"); Future<list<map<string, object>>> future = Es.submit (Newquerydatathread (param)); List<map<string, object>> list =NULL; Try{List=Future.get (); } finally{es.shutdown (); }                returnlist; }}

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More?

Threads that query user data

 Packagecom.nicchagil.study.thread.cnblogs.No02 A thread that can return a value. No002 multiple queries;Importjava.util.ArrayList;ImportJava.util.HashMap;Importjava.util.List;ImportJava.util.Map;Importjava.util.concurrent.Callable;ImportJava.util.concurrent.TimeUnit; Public classQuerydatathreadImplementsCallable<list<map<string, object>>> {        Privatemap<string, object> param =NULL;  PublicQuerydatathread (map<string, object>param) {        Super();  This. param =param; } @Override PublicList<map<string, object>> call ()throwsException {/*get result set after simulating query db*/System.out.println ("Query user param" +param); Map<string, object> map1 =NewHashmap<string, object>(); Map1.put ("id", "1001"); Map1.put ("Name", "Nick Huang."); Map<string, object> map2 =NewHashmap<string, object>(); Map2.put ("id", "1002"); Map2.put ("Name", "Darren Lin"); List<map<string, object>> list =NewArraylist<map<string, object>>();        List.add (MAP1);                List.add (MAP2); /*set a short sleep to see the effect*/        Try{TimeUnit.SECONDS.sleep (3); } Catch(interruptedexception e) {e.printstacktrace (); }                returnlist; }    }

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Thread that queries the address data

 Packagecom.nicchagil.study.thread.cnblogs.No02 A thread that can return a value. No002 multiple queries;ImportJava.util.HashMap;ImportJava.util.Map;Importjava.util.concurrent.Callable;ImportJava.util.concurrent.TimeUnit; Public classQueryextdatathreadImplementsCallable<map<string, object>> {        Privatemap<string, object> param =NULL;  PublicQueryextdatathread (map<string, object>param) {        Super();  This. param =param; } @Override PublicMap<string, object> call ()throwsException {/*get result set after simulating query db*/System.out.println ("Query address param" +param); Map<string, object> map =NewHashmap<string, object>(); Map.put ("1001", "Hz"); Map.put ("1002", "PL"); /*set a short sleep to see the effect*/        Try{TimeUnit.SECONDS.sleep (3); } Catch(interruptedexception e) {e.printstacktrace (); }                returnmap; }    }

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Calls the thread that queries the user data and address data concurrently, merges the data, and returns

 Packagecom.nicchagil.study.thread.cnblogs.No02 A thread that can return a value. No002 multiple queries;ImportJava.util.HashMap;Importjava.util.List;ImportJava.util.Map;Importjava.util.concurrent.ExecutionException;ImportJava.util.concurrent.ExecutorService;Importjava.util.concurrent.Executors;Importjava.util.concurrent.Future; Public classCall { Public Static voidMain (string[] args) {List<map<string, object>> list =NULL; Try{List=query (); } Catch(Exception e) {//TODO auto-generated Catch blockE.printstacktrace (); }                if(List! =NULL&& list.size () > 0) {             for(Map<string, object>map:list)            {System.out.println (map); }        }    }        /*** Business methods for simulating queries*/     Public Staticlist<map<string, object>> query ()throwsinterruptedexception, executionexception {executorservice es=Executors.newcachedthreadpool (); /*simulating query Parameters*/Map<string, object> param =NewHashmap<string, object>(); Param.put ("username", "Derick"); Future<list<map<string, object>>> userfuture = Es.submit (Newquerydatathread (param)); Future<map<string, object>> addressfuture = Es.submit (Newqueryextdatathread (param)); List<map<string, object>> userlist =NULL; Map<string, object> addressmap =NULL; Try{userlist=Userfuture.get (); Addressmap=Addressfuture.get (); } finally{es.shutdown (); }                /*Merging Business Data*/        if(UserList! =NULL&& userlist.size () > 0) {             for(Map<string, object>map:userlist) {Map.put ("Address", Addressmap.get (Map.get ("id")))); }        }                returnuserlist; }}

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Reference API

Callable<v>

Future<v>

Executorservice.submit (java.util.concurrent.Callable)

Interruptedexception

Executionexception

"Multithreading" lets a thread return a value