CODEWITHSUNDEEP
java
John ch
John ch

Reputation: 1

Is type casting possible between wrapper classes in Java?

Is type casting possible between wrapper classes in Java?

The code here is what I tried:

public class Test
{
    public static void main(String[] args)
    {
      Double d = 100.04;  
      Long l = (long) d.doubleValue(); //explicit type casting required  
      int i = (int) l;                 //explicit type casting required  
      System.out.println("Double value " + d);
      System.out.println("Long value " + l);
      System.out.println("Int value " + i);
    }
}

Why isn't Long casted to int in this program?

Upvotes: 0

Views: 6674

Answers (2)

Amit Bhati
Amit Bhati

Reputation: 5649

 Long l = (long)d.doubleValue();  //explicit type casting required  
 int i = (int)l;     //Not valid, because here you are casting a Wrapper Long

In above line, casting of l is not possible to int because Wrapper classes are only by Autoboxing and Unboxing. Refer: https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html. Wrapper class is casted only to its corresponding primitive type.

 long l = (long)d.doubleValue();  //explicit type casting required  
 int i = (int)l;     //valid, because here you are casting primitive to    primitive

In above lines casting of l is possible to int because long is primitive type and int is also a primitive type. Here primitive narrowing casting will take place as casting from long to int may result in loss of some precision.

Upvotes: 2

M A
M A

Reputation: 72844

The Java Language Specification does not allow casting from a reference type to a primitive if it is not by unboxing conversion:

The compile-time legality of a casting conversion is as follows:

  • An expression of a primitive type may undergo casting conversion to another primitive type, by an identity conversion (if the types are the same), or by a widening primitive conversion, or by a narrowing primitive conversion, or by a widening and narrowing primitive conversion.

  • An expression of a primitive type may undergo casting conversion to a reference type without error, by boxing conversion.

  • An expression of a reference type may undergo casting conversion to a primitive type without error, by unboxing conversion.

  • An expression of a reference type may undergo casting conversion to another reference type if no compile-time error occurs given the rules in §5.5.1.

So the only primitive type to which a Long can be cast is long. If you declare the variable of type long (the primitive type), the cast will compile:

long l = (long) d.doubleValue();
int i = (int) l;

Upvotes: 1

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