CODEWITHSUNDEEP
javaarraysobjectint
Siva
Siva

Reputation: 355

Accessing integers from an object of class Object

In the code below an integer array is assigned to an object. If that's possible, why can't i access them through obj? The code compiles, but i get a ClassCastException, I have tried casting the object to String, i get the same error 

public class test
{ public static void main(String ab[])
  { 
   Object obj = new int[] {1,2,3,4,5,6,7,8,9,10};
   Integer[] i = (Integer[]) obj;
   for( Integer c : i)    
   System.out.println(c);       
  }
}

Upvotes: 1

Views: 788

Answers (2)

danielR
danielR

Reputation: 297

It is because you are trying to cast an object of type int[] to an object of type Integer[], that is not possible, although an Integer class can hold int types and in later versions of java you can even assign an int to an Integer like this:

Integer a = 2;

they are different.

If you are using java 5 or above you can do something like this:

public class test
{ public static void main(String ab[])
  { 
   Object obj = new Integer[] {1,2,3,4,5,6,7,8,9,10};
   Integer[] i = (Integer[]) obj;
   for( Integer c : i)    
   System.out.println(c);       
  }
}

Upvotes: 1

Jason C
Jason C

Reputation: 40336

An int[] is not the same as an Integer[].

You create an int[]:

Object obj = new int[] {1,2,3,4,5,6,7,8,9,10};

But then you attempt to cast it back to an Integer[], which you cannot do, because it is an int[]. int[] and Integer[] are both Object, but you cannot cast between the two like that, for the same reason that, e.g., this does not work:

Object obj = new String("");
File f = (File)obj; // obj is a String, will throw ClassCastException

Instead, either create an Integer[] to begin with:

Object obj = new Integer[] {1,2,3,4,5,6,7,8,9,10};
Integer[] i = (Integer[]) obj;

Or use an int[]:

Object obj = new int[] {1,2,3,4,5,6,7,8,9,10};
int[] i = (int[]) obj;

The same is true of your attempt to cast an int[] to a String. You can't convert things just by casting them around in Java.

Upvotes: 2

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