Return different type of data from a method in java

Question

public static void main String args          myMethod       i am calling static method from main           public static   myMethod           what should be the return type     return value    is String     return index    is int     myMethod   will return String and int value  So take these returning values from main   i came up with following solution    create a class call ReturningValues  public class ReturningValues   private String value  private int index      getters and setters here     and change myMethod   as follows     public static ReturningValues myMethod         ReturningValues rv   new ReturningValues        rv setValue  value        rv setIndex 12       return rv      Now my question is there any easier way to achieve this

User · Accepted Answer

Finally i thought my way is better since when number of return types go higher this kind of a implementation do that in best way   public static ReturningValues myMethod     ReturningValues rv   new ReturningValues    rv setValue  value    rv setIndex 12   return rv

User · Answer

I create various return types using enum  It doesn t defined automatically  That implementation look like factory pattern   public  enum  SmartReturn        IntegerType  DoubleType        SuppressWarnings  unchecked       public  lt T gt  T comeback String value            switch  this                case IntegerType                  return  T  Integer valueOf value               case DoubleType                  return  T  Double valueOf value               default                  return null                      Unit Test   public class MultipleReturnTypeTest       Test   public void returnIntegerOrString          Assert assertTrue SmartReturn IntegerType comeback  1   instanceof Integer        Assert assertTrue SmartReturn DoubleType comeback  1   instanceof Double

User · Answer

This can be one of the solution  But your present solution is good enough  You can also add new variables and still keep it clean  which cannot be done with present code   private static final int INDEX OF STRING PARAM   0  private static final int INDEX OF INT PARAM   1   public static Object   myMethod         Object   values   new Object 2       values INDEX OF STRING PARAM     value       values INDEX OF INT PARAM    12      return values

User · Answer

Generally if you are not sure of what value you will end up returning  you should consider using return-type as super-class of all the return values  In this case  where you need to return String or int  consider returning Object class which is the base class of all the classes defined in java    But be careful to have instanceof checks where you are calling this method  Or else you may end up getting ClassCastException   public static void main String args              Object obj   myMethod       i am calling static method from main   which return Object     if obj instanceof String          Do something      else obj instance of Integer          do something else

User · Answer

public ArrayList divineCast String object              try                       Integer result   Integer parseInt object               ArrayList lt Integer gt  generic   new   ArrayList lt Integer gt                 generic add result               return generic                    catch Exception e                          not a Integer                   try                       Float result   Float parseFloat object               ArrayList lt Float gt  generic   new   ArrayList lt Float gt                 generic add result               return generic                    catch Exception e                          not a Float                   try                       Double result   Double parseDouble object               ArrayList lt Double gt  generic   new   ArrayList lt Double gt                 generic add result               return generic                    catch Exception e                          not a double                   try                       Boolean result   Boolean parseBoolean object               ArrayList lt Boolean gt  generic   new   ArrayList lt Boolean gt                 generic add result               return generic                    catch Exception e                          not a Boolean                   try                       String result   String valueOf object               ArrayList lt String gt  generic   new   ArrayList lt String gt                 generic add result               return generic                    catch Exception e                          not a String                   return null           Then you can call then function as so  String test1    0 90854938   String test2    true   System out println divineCast test1  get 0    System out println divineCast test1  get 0  getClass     System out println divineCast test2  get 0    System out println divineCast test2  get 0  getClass       Java doesn t force you to declare the type of ArrayList you are returning in the function declaration  so you can return an ArrayList of any type

User · Answer

No  Java methods can only return one result  void  a primitive  or an object   and creating a struct-type class like this is exactly how you do it   As a note  it is frequently possible to make classes like your ReturningValues immutable like this   public class ReturningValues       public final String value      public final int index       public ReturningValues String value  int index            this value   value          this index   index            This has the advantage that a ReturningValues can be passed around  such as between threads  with no concerns about accidentally getting things out of sync

User · Answer

ruchira ur solution it self is best But i think if it is only about integer and  a string we can do it in much easy and simple way     class B          public String myfun                      int a 2              Integer    you could use scanner or pass parameters   i have simply assigned         String b  hi          String         return Integer toString a      b    returnig string and int with     in middle                           class A           public static void main String args              B obj new B        obj of class B with myfun   method           String returned   obj myfun   split                      splitting integer and string values with     and storing them in array            int b1 Integer parseInt returned 0      converting first value in array to integer              System out println returned 0      printing integer             System out println returned 1      printing String           i hope it was useful

User · Answer

I just want to put my view   So you need to create a generic Return type and implemented by different types of concret return types  The Service class can create different types of objects concrete class and return as a generic type   public interface GenericReturnType      public static RETURN TYPE enum          MACHINE  PERSON                public RETURN TYPE getReturnType       public class PersonReturnType implements GenericReturnType         CONSTRUCTORS            GETTRE AND SETTER         public RETURN TYPE getReturnType            return PERSON            public String getAddress            return something           public class MachineReturnType implements GenericReturnType         CONSTRUCTORS            GETTRE AND SETTER         public RETURN TYPE getReturnType            return MACHINE            public String getManufatureName            return something            public class TestService      public GenericReturnType getObject    some input              GenericReturnType obj           if    some code                  obj   new  PersonReturnType                   some code                      if    some code                  obj   new  MachineReturnType                   some code                      return obj           public class TestDriver      TestService service   new TestService        GenericReturnType genObj   TestService getObject    some input          if genObj getReturnType      RETURN TYPE MACHINE              SOME CODE               if genObj getReturnType      RETURN TYPE PERSON              SOME CODE

User · Answer

you can have the return as an object  You create that object  on fly  in your   function  if int    return new object       int nr        same for string  But I am concerned that is an expensive solution

User · Answer

Method overloading can come in handy here Like    lt code gt  public class myClass        int add int a  int b                  return  a   b              String add String a  String b                 return  c   d              public static void main String args                   myClass ob1   new myClass           ob1 add 2  3             will return 5         ob1 add  Hello      World               will return Hello  World

User · Answer

I know this is late but I thought it d be helpful to someone who ll come searching for an answer to this  You can use a Bundle to return multiple datatype values without creating another method  I tried it and worked perfectly       In Your MainActivity where you call the method    Bundle myBundle   method    String myString   myBundle getString  myS    String myInt   myBundle getInt  myI         Method    public Bundle method         mBundle   new Bundle        String typicalString    This is String       Int typicalInt   1      mBundle putString  myS   typicalString       mBundle putInt  myI   typicalInt       return mBundle      P S  I m not sure if it s OK to implement a Bundle like this  but for me  it worked out perfectly

User · Answer

The class you re looking for already exists   Map Entry   public static Entry lt Integer String gt  myMethod        return new SimpleEntry lt  gt  12   value        And later   Entry lt Integer String gt  valueAndIndex   myMethod    int index   valueAndIndex getKey    String value   valueAndIndex getValue      It s just a simple two-field data structure that stores a key and value   If you need to do any special processing  store more than two fields  or have any other fringe case  you should make your own class  but otherwise  Map Entry is one of the more underutilized Java classes and is perfect for situations like these

User · Answer

the approach you took is good   Just Implementation may need to be better  For instance ReturningValues should be well defined and Its better if you can make ReturningValues as immutable      this approach is better public static ReturningValues myMethod         ReturningValues rv   new ReturningValues  value   12       return rv      public final class ReturningValues       private final String value      private final int index        public ReturningValues String value  int index          this value   value        this index   index               Or if you have lots of key value pairs you can use HashMap then   public static Map lt String Object gt  myMethod       Map lt String Object gt  map   new HashMap lt String Object gt       map put VALUE   value      map put INDEX  12     return Collections unmodifiableMap map      try to use this

[java] Return different type of data from a method in java?

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