Java newbie help (type casting, 64bit unsigned Long)

Hi I am java newbie and need help on my project. I have a few questions. Can you put strings in a hashtable and test for their being their with the appropriate hashtable method? I want to test for equal strings, not the same object. Second question can you use all 64 bits of an unsigned long? java doesn't seem to allow this. Any packages that do?
Thanks,
Dave

Try casting it to Long instead of long. Long (capital L) is an Object, while long (lower case l) is not. You may also check to make sure the value isn't null. I would have thought that autoboxing would have worked here unless the value was null. But I am no expert on autoboxing.
Edit >> Checking for null ain't a bad idea but has nothing to do with the problem - this is a compile time problem. Sorry.
Also>> This code should work:
long cTime=(Long)session.getAttribute("creationtime");Edited by: stevejluke on Jul 1, 2008 11:00 AM

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Java newbie help: Need to change a graphic on screen

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FWIW, the project is being developed with Netbeans.
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Help?!?

FWIW, the project is being developed with Netbeans.
In case you don't know, you can use any editor to develop java code.
What I'm after is how to change a graphic object onscreen from within the code, vs. with a device such as a mouse. I'm trying to emulate an LED indicator.
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What happend?
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Is this not what you wanted?

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else
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Unsigned Long in java

Hi all,
I have a code in C which i want to convert into java.. Iam facing problem because java does not support
unsigned long.The code in c look like this:
WCD.cardno = ( SerBuf[3]* 0x00010000UL+
SerBuf[4]* 0x00000100UL+
SerBuf[5]* 0x00000001UL);
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cardno = (tempBuffer[3]*0x01000000 + tempBuffer[4]*0x00010000 + tempBuffer[5]*0x00000100 +tempBuffer[6]*0x00000001);
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Thanks
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kiranJNI wrote:
Basically how can we achieve unsigned long in java???In your case, this isn't going to be a problem for two reasons.
AFAIK, there aren't any numbers where multiplying them as unsigned numbers is going to be different from multiplying them as signed numbers and still give a valid result. To make this easier, let's work with signed vs unsigned bytes. Negative numbers are those in the range 0x80 to 0xFF; these are the only numbers where the "value" of the byte differs between signed and unsigned. Now think of those numbers as unsigned numbers. The only unsigned numbers you could multiply them by and still remain within the range of a byte are 0 and 1. If you multiply by 2, the result is 0x100, which is larger than what a byte can represent. If the result will remain within the range of the data type, it don't think there are any numbers where signed and unsigned multiplication return a different bit pattern.
Furthermore, your example doesn't even need multiplication. You're multiplying by powers of 2, so all you really need is a series of shifts and adds.

Urgent::Unsigned Long Requirement::Oracle Number(38) to Java conversion

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Currently, I am storing it as follows:
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Currently, I am storing it as follows:
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JAVA primitive data types - Signed/ unsigned etc.

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byte, short, int, long, float, double
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And to answer your first question, byte, short, int, long, float and double are all signed.
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DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
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Could you try using the bpelx:rename extension in an assign activity enables a BPEL process to rename an element through use of XSD type casting.
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A

Do week-long java courses help to understand java & get a job?

i tried searching for this topic before posting, but "courses" "classes" & "instruction" come up with a lot that has nothing to do with the topic at hand. :)
like many others, i'm teaching myself out of a book (Deitel). so far i've been able to understand the material and create programs based on the exercises. however, i'm now into the meat of OOP with superclass, subclasses, how they interact and the like and i'm having a rough go of it. i can diagram and understand the abstract concept, but when i'm faced with an actual program example i have a difficult time following the interactions between classes.
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I took a week long course to learn Java. It worked I did learn the basics of Java but I did already know how to program in C and VB at the time. I found the AWT section of the class to be very valuable,cosidering I mostly write GUI. And the concepts of AWT mostly all apply to swing so that didn't set me back at all. Depending on the school it may help you to understand OOP. But be careful because most schools progress the class at the skill level of the majorty. So if you have 15 people in the class and 9 of them know nothing about programing your probably going to spend the week learning what a variable and a while loop do, you all pay the same tuition and they would rather 6 of you leave then 9 of you leave. If you have some prior programming knowledge I would recomend finding a class that caters to that.

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Hello,
This is my requirement.
I have a method that takes class name as a parameter.
Ex:
Object myMethod(String classname){
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In the above example, how can i dynamically typecast the object with class whose name is passed as the method parameter?

Hello,
This is my requirement.
I have a method that takes class name as a parameter.
Ex:
Object myMethod(String classname){
Object xyz = getObject(); //userdefine method which
returns some object
/*I need to typecast above object with the class
name passed as the method parameter*/
/*How can i type cast this object*/
Object obj = (classname) xyz;
return obj;
In the above example, how can i dynamically typecast
the object with class whose name is passed as the
method parameter?Perhaps a little more background on the project (what you are trying to do) will help the experts here answer?
/*with a class that takes a noarg constructor*/
public Object getObject(String classname) throws Exception
//might want to get a bit more specific with which exceptions it will throw
return Class.forName(classname).newInstance();
}Do I think this sometimes is indicative (perhaps even more often than not), of a possible design flaw? Yes..
It gets a little trickier if you have constructors (you have to create a Class object representing the string with the .forName(..) ..and then use some reflection to determine constructors and then a bit of logic to determine which of those to use...)
~Dave

Type casting in Java

Hi,
Can we do explicit type casting vigorously in a java class? Im in a situation that i've to do explicit casting 40 to 50 times in a class. Is there any overhead for JVM or any performance issue with this?

Why do you cast so often? It's sounds like a weird design. Casting is pretty cheap.
Kaj

Unsigned Long declaration in JAVA ?????

Hi,
Java doesnt allow unsigned declaration.
I have a 'C' program which does the following:
unsigned long someLongInteger; //in C
someLong>>18;
SomeLong<<14;
SomeLong>>=14;
When I did the same thing in JAVA by declaring someLongInteger as long, it gives me a different result.
Is that because it is considering java Long as signed??
Is there any work around this?
I appreciate your reply
Thank you.

Depending on what you are trying to do, the unsigned right shift operator (>>>) may be of use for this situation.
- K
Hi,
Java doesnt allow unsigned declaration.
I have a 'C' program which does the following:
unsigned long someLongInteger; //in C
someLong>>18;
SomeLong<<14;
SomeLong>>=14;
When I did the same thing in JAVA by declaring
someLongInteger as long, it gives me a different
result.
Is that because it is considering java Long as
signed??
Is there any work around this?
I appreciate your reply
Thank you.

Java type casting interesting query

In java semantics
1) float var1=10.5; // is wrong it should be written as
float var1=(float)10.5; //type casting->double to float
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float var1=10.5f; //type casting
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2) byte var2=10; // here int to byte type casting should be there according to previous eg.
But this is correct.
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>
I suspect the reason is, that the compiler can check whether it will fit in the second case.
You can't accidentally type
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64bit unsigned int - j????

I have a 64bit unsigned int in a datastructure generated by a native method.
What would be the best java type to cast it to, before returning the value?
Thanks,
Than

BigInteger is the only java "datatype" that can handle this if you need to access the unsigned value within your Java code. None of the primitive datatypes will work as they are all signed.
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Parsing binary file- unsigned longs

Hello everyone.
I'm currently trying to write a quick parser for a binary file format (ASF). However, java's handling of bit shifting and lack of unsigned types is driving me completely mad.
How can I represent an unsigned long?
How can I set the bits for it anyway? It seems that the shift operator can't shift more than an int's worth (it just loops around and starts adding to the other bits- weird).
Thanks in advance.
Simon

ejp wrote:
But why in the world does the following code also do nothing?
long x = 45 << 32;
Try long x = 45L << 32;
The answer appears to be that java uses ints to represent all constants, but this presents some serious problems- namely- how on earth do you get a number bigger than an int into a long?With 'L'. Same as in C or C++. In Visual Basic it's '&'. There's generally something.Where did that come from? Why have I never seen anything like that before?
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As someone pointed out signed/unsigned is actually the same, so long as you interpret it correctly. So to avoid the total stupidity of using twice as much memory for everything I've decided that I am actually going to use the correct types.They're not the correct types. As I pointed out in an earlier post, your 'unsigned longs' must be coming from C or C++ where they are generally 32 bits, so using a 64-bit Java long is incorrect.Where they came from doesn't matter. The spec doesn't say it's a "long"- it says that this particular value is 64bit, and that all values are unsigned. So I do need a Java long.
WHY IN THE WORLD IS JAVA "INTELLIGENT" WHEN DOING THINGS BITWISE? WHICH BRAIN DEAD IDIOT THOUGHT THAT UP? That is broken and is asking for trouble.It is you who is asking for trouble here. The rules of Java are consistent and in conformity with the practice in other programming languages. You've just overlooked several relevant facts.I think I've worked out where I was going wrong here. When doing something like
int i;
long x;
x = x | i;The i is converted to a long before the bitwise operation, so it's not the bitwise operation that's the problem, it's the conversion between int and long?
It's not Java whose stupidity is the issue here ;-)That wouldn't surprise me.
Thanks.

Type Casting Exception

I have an attribute CategoryId in my VO of type oracle.jbo.domain.Number. I am trying to use the expression of Boolean item in JHS as #{row.CategoryId != 4}
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Java newbie help (type casting, 64bit unsigned Long)

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