Solved

Bitwise Copy

Posted on 2000-05-15
4
246 Views
Last Modified: 2006-11-17
Hi,
I have an int i=0xffffffff which I want to copy to a long l , so that the result is l=0x00000000ffffffff; , Can you pls tell me how to do it.

thanks in advance
regards
mak
0
Comment
Question by:makrand
  • 2
  • 2
4 Comments
 
LVL 16

Accepted Solution

by:
imladris earned 100 total points
ID: 2811699
There should be no special handling required:

int i=0xffffffff;
long l=i;

Since l is a "wider" type than i, it can be assigned without any trouble at all.
0
 

Author Comment

by:makrand
ID: 2811903
When u check the binary value of it using
Long.toBinaryString(longVal) and
Integer.toBinaryString(intVal), you will notice the diffrence
0
 
LVL 16

Expert Comment

by:imladris
ID: 2812385
Yes, you are quite right. I apologize. The reason for the behaviour you see is that integers (and longs) are signed quantites. The value 0xffffffff represents -1 in an integer. When it is converted to a long, the sign bit is extended leftward (i.e. if the topmost bit is 0 the top 4 bytes of the long are set to 0, but if the top bit is 1 the top 4 bytes of the long are set to 1). Thus the long becomes 0xffffffffffffffff which also represents -1.

To force the long to contain 0xffffffff you will need to mask the top 4 bytes to 0:

long l=i&0xffffffffL;

Make sure you add the L to the constant which will cause the constant to be long (i.e. 8 bytes). This will cause the variable i to be widened (and sign extended) (in order to do the bitwise operation), then top 4 bytes will by masked off.

Without the trailing L, the bitwise operation would occur first (having no effect) and then the result would be widened (leaving you with the sign extension again.
0
 

Author Comment

by:makrand
ID: 2818431
Thanks very much, I was not getting the exact way to do a bitwise operation, I was doing something like this

private static long getBinaryLongValue(int val)
{
String s = Integer.toBinaryString(val);
long l = Long.parseLong(s,2);
return l;  
             
}
0

Featured Post

Free Tool: Postgres Monitoring System

A PHP and Perl based system to collect and display usage statistics from PostgreSQL databases.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
fibonacci ten numbers 4 45
hibernate example for saving data 19 54
jsp insert to database example 2 46
Fast way to search item into Java Array (Rhino compatible) 2 31
INTRODUCTION Working with files is a moderately common task in Java.  For most projects hard coding the file names, using parameters in configuration files, or using command-line arguments is sufficient.   However, when your application has vi…
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.

860 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question