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structure/package data types..

Posted on 2005-04-13
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Last Modified: 2013-12-03
hi,

working on java 1.5 for windows platform.

I have a base class CMainBase and have 4 classes derived from it , cboolean,

cintvalue, cstring and cother.

every data type(boolean, intvalue, string, other) has some attribute(s ) associated with it.

read-only,
read-write,
execute-only,
hidden.

these attribute, can be any or combination for each datatype (string,

boolean, other, value). The length of each attribute is 1 byte.

I am planning to make a structure containing alll these types like:

public abstract class CMainBase {

class attrib{
byte read-only;
byte read-write;
byte execute-only;
byte hidden;
}
}

and then use the same. Is this the right way to proceed ?? How to use this

class to package all the attribtutes so that overall length should not exceed 1 byte ?? i mean to say looking at the value i can deduce the attributes present for a datatype.

All suggestion are welcome.  

Regards,
rdh

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Question by:rohitdivas
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4 Comments
 
LVL 15

Expert Comment

by:aozarov
ID: 13774048
You can have one int variable (e.g int attributes)
and then have constants like:
public int READ = 1;
public int WRITE = 2;
public int EXECUTE = 4;
...

(each value is bigger then its previous one by multiply of 2).
Then you can assing to a type something like this:

intvalue intVal = ..
intVal.setAttributes( READ | WRITE); // or READ + WRITE;
which means that this value has RW attibutes.
If you want to check if this value has WRITE persmissions then you can do something like this:

if ((intVal & WRITE) > 0) ... // then this value has write persmissions.
There are many examples of the JDK for such technique (e.g. http://www.docjar.org/html/api/java/awt/Font.java.html)
0
 
LVL 15

Expert Comment

by:aozarov
ID: 13774085
For the Font class it is they way its store its style atributes (PLAIN , BOLD, ITALIC)
or FlowLayout with its alignment attributes: http://www.docjar.org/html/api/java/awt/FlowLayout.java.html
0
 

Author Comment

by:rohitdivas
ID: 13779109
The combination of all of them should not exceed 1 byte.  but here it is exceeding.

i need to achieve the functionality provided by enum data type (and enum is not provided in java) .  The method suggested by you will work, but  i am in search of alternatives methods.

rdh
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LVL 15

Accepted Solution

by:
aozarov earned 600 total points
ID: 13781044
You can still use byte and apply the same technique (as long as you have less then 8 combinations).
public byte READ = (byte) 1;
public byte WRITE = (byte) 2;
public byte EXECUTE = (byte) 4;
public byte HIDDEN = (byte) 8;

There is enum in Java 5.0 http://java.sun.com/j2se/1.5.0/docs/guide/language/enums.html
Though they will not be one byte only (they are treated as objects).

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