How to cast an Object to an int in java?

Question

How can I cast an Object to an int in java?

Answer 1

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.

Answer 2

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.

Answer 3

You can't. An int is not an Object.

Integer is an object though, but I doubt that's what you mean.

Answer 4

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

Answer 5

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.

Answer 6

If you're sure that this object is an Integer :

int i = (Integer) 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.

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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.

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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

Answer 7

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

Answer 8

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

Answer 9

int i = (Integer) object; //Type is Integer.

int i = Integer.parseInt((String)object); //Type is String.

Answer 10

@Deprecated
public static int toInt(Object obj)
{
    if (obj instanceof String)
    {
         return Integer.parseInt((String) obj);
    } else if (obj instanceof Integer)
    {
         return ((Integer) 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.

Answer 11

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.

Answer 12

first check with instanceof keyword . if true then cast it.