How to cast an Object to an int

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How can I cast an Object to an int in java

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Scenario 1  simple case  If it s guaranteed that your object is an Integer  this is the simple way   int x    Integer yourObject      Scenario 2  any numerical object  In Java Integer  Long  BigInteger etc  all implement the Number interface which has a method named intValue  Any other custom types with a numerical aspect should also implement Number  for example  Age implements Number   So you can   int x     Number yourObject  intValue      Scenario 3  parse numerical text  When you accept user input from command line  or text field etc   you get it as a String  In this case you can use Integer parseInt String string    String input   someBuffer readLine    int x   Integer parseInt input     If you get input as Object  you can use  String input  or  if it can have an other textual type  input toString     int x   Integer parseInt input toString       Scenario 4  identity hash  In Java there are no pointers  However Object has a pointer-like default implementation for hashCode    which is directly available via System identityHashCode Object o   So you can   int x   System identityHashCode yourObject     Note that this is not a real pointer value  Objects  memory address can be changed by the JVM while their identity hashes are keeping  Also  two living objects can have the same identity hash   You can also use object hashCode    but it can be type specific   Scenario 5  unique index  In same cases you need a unique index for each object  like to auto incremented ID values in a database table  and unlike to identity hash which is not unique   A simple sample implementation for this   class ObjectIndexer        private int index   0       private Map lt Object  Integer gt  map   new WeakHashMap lt  gt          public int indexFor Object object            if  map containsKey object                 return map get object             else               index                map put object  index               return index                       Usage   ObjectIndexer indexer   new ObjectIndexer    int x   indexer indexFor yourObject         1 int y   indexer indexFor new Object         2 int z   indexer indexFor yourObject         1   Scenario 6  enum member  In Java enum members aren t integers but full featured objects  unlike C C    for example   Probably there is never a need to convert an enum object to int  however Java automatically associates an index number to each enum member  This index can be accessed via Enum ordinal    for example   enum Foo   BAR  BAZ  QUX            Object baz   Foo BAZ  int index     Enum baz  ordinal       1

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For Example Object variable  hastaId  Object hastaId   session getAttribute  hastaID        For Example Cast an Object to an int hastaID  int hastaID Integer parseInt String valueOf hastaId

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int   getAdminIDList String tableName  String attributeName  int value  throws SQLException       ArrayList list   null      Statement statement   conn createStatement        ResultSet result   statement executeQuery  SELECT admin id FROM     tableName     WHERE     attributeName          value             while  result next              list add result getInt 1              statement close        int id     new int list size         for  int i   0  i  lt  id length  i              try               id i      Integer  list get i   intValue              catch NullPointerException ne              catch ClassCastException ch               return id       enter code here   This code shows why ArrayList is important and why we use it  Simply casting int from Object  May be its helpful

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first check with instanceof keyword   if true then cast it

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Answer   int i     Integer   yourObject    If  your object is an integer already  it will run smoothly  ie   Object yourObject   1      cast here   or  Object yourObject   new Integer 1       cast here   etc   If your object is anything else  you would need to convert it   if possible   to an int first   String s    1   Object yourObject   Integer parseInt s       cast here   Or  String s    1   Object yourObject   Integer valueOf  s        cast here

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Refer This code     public class sample      public static void main String   args           Object obj new Object        int a 10 b 0      obj a      b  int obj       System out println  Object   obj   nB   b

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int i    Integer  object    Type is Integer   int i   Integer parseInt  String object     Type is String

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so divide1 me getValue   2   int divide1    Integer  me getValue   2

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If the Object was originally been instantiated as an Integer  then you can downcast it to an int using the cast operator  Subtype    Object object   new Integer 10   int i    Integer  object    Note that this only works when you re using at least Java 1 5 with autoboxing feature  otherwise you have to declare i as Integer instead and then call intValue   on it   But if it initially wasn t created as an Integer at all  then you can t downcast like that  It would result in a ClassCastException with the original classname in the message  If the object s toString   representation as obtained by String valueOf   denotes a syntactically valid integer number  e g  digits only  if necessary with a minus sign in front   then you can use Integer valueOf   or new Integer   for this   Object object    10   int i   Integer valueOf String valueOf object      See also    Inheritance and casting tutorial

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Finally  the best implementation for your specification was found   public int tellMyNumber Object any        return 42

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Can t be done  An int is not an object  it s a primitive type  You can cast it to Integer  then get the int    Integer i    Integer  o     throws ClassCastException if o getClass      Integer class   int num   i    Java 1 5 or higher

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I guess you re wondering why C or C   lets you manipulate an object pointer like a number  but you can t manipulate an object reference in Java the same way   Object references in Java aren t like pointers in C or C       Pointers basically are integers and you can manipulate them like any other int   References are intentionally a more concrete abstraction and cannot be manipulated the way pointers can

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You can t  An int is not an Object   Integer is an Object though  but I doubt that s what you mean

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If you re sure that this object is an Integer    int i    Integer  object    Or  starting from Java 7  you can equivalently write   int i    int  object    Beware  it can throw a ClassCastException if your object isn t an Integer and a NullPointerException if your object is null   This way you assume that your Object is an Integer  the wrapped int  and you unbox it into an int   int is a primitive so it can t be stored as an Object  the only way is to have an int considered boxed as an Integer then stored as an Object     If your object is a String  then you can use the Integer valueOf   method to convert it into a simple int    int i   Integer valueOf  String  object     It can throw a NumberFormatException if your object isn t really a String with an integer as content     Resources     Oracle com - Autoboxing Oracle com - Primitive Data types   On the same topic     Java  What s the difference between autoboxing and casting  Autoboxing  So I can write  Integer i   0  instead of  Integer i   new Integer 0   Convert Object into primitive int

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Deprecated public static int toInt Object obj        if  obj instanceof String                 return Integer parseInt  String  obj         else if  obj instanceof Number                 return   Number  obj  intValue          else                String toString   obj toString             if  toString matches  -  d                              return Integer parseInt toString                       throw new IllegalArgumentException  This Object doesn t represent an int              As you can see  this isn t a very efficient way of doing it  You simply have to be sure of what kind of object you have  Then convert it to an int the right way

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I use a one-liner when processing data from GSON   int i   object    null   Double valueOf object toString    intValue     0

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If you mean cast a String to int  use Integer valueOf  123     You can t cast most other Objects to int though  because they wont have an int value  E g  an XmlDocument has no int value

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You have to cast it to an Integer  int s wrapper class   You can then use Integer s intValue   method to obtain the inner int

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Assuming the object is an Integer object  then you can do this    int i     Integer  obj  intValue      If the object isn t an Integer object  then you have to detect the type and convert it based on its type

[java] How to cast an Object to an int

Scenario 1: simple case

Scenario 2: any numerical object

Scenario 3: parse numerical text

Scenario 4: identity hash

Scenario 5: unique index

Scenario 6: enum member

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