330 Java Tips.pdf - FTP Server

String, text, numbers, I/O II part
Check out the % (modulus) operator, it computes the remainder.
public int modMethod(int div){
if(div%2==0){
return 1;
} else{
return 0;
}
}
Q: How can I round a number to specified precision?
I have a double field that I would like to round to 2 places of precision, however, it
seems like the documentation on the round function only rounds to
closest integers. So that I would not be able say .3658585859 = .37 as
I would like.
Answer: can you scale the number up and then down again when you are finished?
e.g. 0.3658585859 * 100 = 36.58585859
round(36.58585859) = 37
37 / 100 = 0.37
I understand that bitwise operations change the 0/1 bits of a number. Question is
why?
I suppose it's interesting that you can manipulate numbers this way, but I can't think
of a practical use for doing that.
Can anyone help me understand when are bitwise operations used and why you
would use them?
Answer: Bitwise manipulation is often used where memory consumption is critical,
and a piece of information may be encoded in less that one byte, for instance. In
communication software and protocols, information may be interpreted as a stream
of bits where the information is encoded at the bit-level, and you use bitwise
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
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