MAX_VALUE and Casting

[Cory Max]

    
System.out.println("int maxvalue = " + Integer.MAX_VALUE);
int i = Integer.MAX_VALUE;
System.out.println("int maxvalue" + i);

System.out.println("long maxvalue = " + Long.MAX_VALUE);
i = (int)Long.MAX_VALUE;
System.out.println("long maxvalue cast to an int " + i);

System.out.println("double maxvalue = " + Double.MAX_VALUE);
i = (int)Double.MAX_VALUE;
System.out.println("double maxvalue cast to an int " + i);

Output:

[CODE]
int maxvalue = 2147483647
int maxvalue2147483647
long maxvalue = 9223372036854775807
long maxvalue cast to an int -1
double maxvalue = 1.7976931348623157E308
double maxvalue cast to an int 2147483647
/CODE]

Why when you cast a double to an int you get -1 (because it is too big), but when you cast a double, you get the max value for integer?

Thanks again,

Cory

[Prasad Tamirisa]

Doesn't it mean that, it is out of range.

The maximum value of double will defnately be out of range of integer..!

[Chandra Bhatt]

Strange!!!


Eager to know the reason.




@cmbhatt

[Henry Wong]

The explicit cast from long to int is different from the explicit cast from a double to int.

For double to int, it actually has to convert the bits. Examine the value as a double and then convert it to the nearest int value.

For long to int, it just assumes that you know what you are doing and truncates the 4 high bytes. And believe it or not, if you take only the 4 low bytes of a Long.MAX_VALUE, you get the bit pattern for -1.

Henry

[Cory Max]

And believe it or not, if you take only the 4 low bytes of a Long.MAX_VALUE, you get the bit pattern for -1.

I think I must be misunderstanding something. Wouldn't the 4 low bytes of a Long.MAX_VALUE be 32 1's? The first one being a sign bit then the remaining 31 being 2147483647?

[Henry Wong]

I think I must be misunderstanding something. Wouldn't the 4 low bytes of a Long.MAX_VALUE be 32 1's? The first one being a sign bit then the remaining 31 being 2147483647?

The low 4 bytes of Long.MAX_VALUE is indeed 32 1's. And ....

11111111 11111111 11111111 11111111 == -1

Remember that Java uses 2's complement to represent integers.

Henry