String, text, numbers, I/O II part

manipulation to extract the pieces of information encoded in the bytes. There are

other situations where bitwise manipulation is used, as well.

by Greger Ohlson

 Why cannot I cast from double to java.lang.Object?

Q: I m trying to build a vector, however, one of the objects that I m passing to the

vector is of type double. How do I cast the double as an object so that I may insert

the value into a vector? Does this make sense? Here is the following snippet of code

I was trying to use:

myVector.add (1, (Object)myDouble);

Of course when I try to compile I get the following message:

Invalid cast from double to java.lang.Object

Could someone please explain why? I realize that Object is the mother of all objects

and therefore ANY reference data type "is an" Object. So therefore I shouldn t have

to cast the double, right? Help, I m a beginner!

Answer: A double is not a reference type, but a primitive one. Hence, it doesn t

inherit from Object (or anything else, for that matter). To put primitives (byte, short,

int, long, float, double, boolean, char) into something that requires an Object, use

Java s wrapper classes.

The wrapper classes are Double, Integer, Long, Boolean, etc., and are basically an

object "wrapped" around a primitive type. You make a Double object by:

Double d = new Double (myDouble);

and to get the actual value back,

double z = d.doubleValue();

It works the same way for all the rest of the primitive/wrapper pairs.

by Trevor Hill

Q: is there a mod (x, y) function that returns the remainder when x is divided by

y? Something equivalent to fmod(x,y) in C?

Answer: a = x%y;

I m having trouble figuring out how to convert characters to their ASCII value in

java

Q: I m having trouble figuring out how to convert characters to their ASCII

value in java. Is there a class like NumberFormat that will do it?

Answer: I can t see any problem here:

char ch =  A ; // character  A 

int i = (int)ch; // ASCII value for  A  (=>65)

Yes. And just be aware that ASCII only runs from 0 through 127. Anything

higher needs to be addressed differently, since Java is using Unicode values.

 Q: I m writing a program that makes I/O on a (huge) file.

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