Byte and char !!!

Hi!
What is the diference between an byte and char in Java! Could I use char instead of byte and reverse?
Thanks.

TYPE BYTE BITS SIGN RANGE
byte 1 8 SIGNED -128 to 127
char 2 16 UNSIGNED \u0000 to \uFFFF
Both the date types can be interchanged
Have a look at this
class UText
     public static void main(String[] args)
          byte c1;
          char c2= 'a';
          c1 = (byte) c2;
          c2 = (char) c1;
          System.out.println(c1 +" "+c2);
But It Leads to confusion while interchanging because of its SIGN. And the range of byte is very less.So its better to prefer char.

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Mixing byte and char input

Hi,
I have a setup where I wish to arbitarily read bytes or chars from the same underlying input stream, under jdk 1.3.x.
As far as I can see, InputStreamReader will always always over-read from the underlying stream (to the tune of 8k, if it can) and never replace the data it didn't use. This could be removing data that should have been read as binary data, and thus corrupting the stream.
Given that there's no way, it seems, of detecting the number of bytes per character for a given encoding, the only solution that I can think of is to provide an intermediate buffering stream that drip feeds the reader a conservative number of bytes. This obviously has profound efficiency implications if the reader has to re-fill() itself that often.
Has anyone else sucessfully dealt with this problem?

I'm still not
sure I understand the problem. Is it that the char
reader will keep reading past the chars removing the
binary data from what is left to be read and
preventing it from being read by a 'binary' reader?Yes - InputStreamReader, one of two ways to ensure that byte to char conversion is done properly pre-1.4, will use a fixed buffer size of 8192 bytes to read from the underlying stream.
It seems that you may need to read in everything as
binary data and delegate chars off to another Reader
as you come across them. Of course you will have to
know when the data should be interpreted as chars and
when it should not. Only acheivable insofar as the underlying mechanism will be told by clients what to read(i.e. readLine() / readBytes(), or something).
Some sort of home-rolled throttle between the underlying stream and the reader seems to be the only option, but this will be really clunky.
There will have to be some sort
of separator between the types. Am I understanding
that this will be used with several different
protocols?Yes, potentially a large number (this will, eventually, be a port of the Indy set of components for Delphi, http://www.nevrona.com/indy, FYI).

Oracle Best practices for changing Byte to Char on Varchar2 columns

Dear Team,
Application Team wanted to change Byte to Char on Varchar2 columns to accommodate Multi byte character on couple of production tables.
Wanted to know is it safe to have mixture of BYTE and CHAR semantics in the same table i have read on the couple of documents that It's good practice to avoid using a mixture of BYTE and CHAR semantics columns in the same table.
What happens if we have mixture of BYTE and CHAR semantics columns in the same table?
Do we need to gather stats & rebuild indexes on the table after these column changes .
Thanks in Advance !!!
SK

Application Team wanted to change Byte to Char on Varchar2 columns to accommodate Multi byte character on couple of production tables.
Wanted to know is it safe to have mixture of BYTE and CHAR semantics in the same table i have read on the couple of documents that It's good practice to avoid using a mixture of BYTE and CHAR semantics columns in the same table.
No change is needed to 'accommodate Multibyte characters'. That support has NOTHING to do with whether a column is specified using BYTE or CHAR.
In 11g the limit for a VARCHAR2 column is 4000 bytes, period. If you specify CHAR and try to insert 1001 characters that each take 4 bytes you will get an exception since that would require 4004 bytes and the limit is 4000 bytes.
In practice the use of CHAR is mostly a convenience to the developer when defining columns for multibyte characters. For example for a NAME column you might want to make sure Oracle will allocate room for 50 characters REGARDLESS of the actual length in bytes.
If you provide a name of 50 one byte characters then only 50 bytes will be used. Provide a name of 50 four byte characters and 200 bytes will be used.
So if that NAME column was defined using BYTE how would you know what length to use for the column? Fifty BYTES will seldom be long enough and 200 bytes SEEMS large since the business user wants a limit of FIFTY characters.
That is why such columns would typically use CHAR; so that the length (fifty) defined for the column matches the logical length of the number of characters.
What happens if we have mixture of BYTE and CHAR semantics columns in the same table?
Nothing happens - Oracle could care less.
Do we need to gather stats & rebuild indexes on the table after these column changes .
No - not if you by 'need' you mean simply because you made ONLY that change.
But that begs the question: if the table already exists, has data and has been in use without their being any problems then why bother changing things now?
In other words: if it ain't broke why try to fix it?
So back to your question of 'best practices'
Best practices is to set the length semantics at the database level when the database is first created and to then use that same setting (BYTE or CHAR) when you create new objects or make DDL changes.
Best practices is also to not fix things that aren't broken.
See the 'Length Semantics' section of the globalization support guide for more best practices
http://docs.oracle.com/cd/E11882_01/server.112/e10729/ch2charset.htm#i1006683

Using byte or char array?

I am trying to use byte[] or char[] to read from a socket. I used byte[] and char[], both works fine. However, I know byte is 8 bits and char is 16 bits. Does it matter which one I used?
Thanks.

When you deal with streams of plain bytes you should use input/outputstreams, not readers or writers that are meant for character streams. The inputstream equivalent to BufferedReader is BufferedInputStream and there is a method for reading a full byte[] there...
But using a "bigger" data type than you need will not cause you big problems.

Form English Char ( Single Byte ) TO Double Byte ( Japanese Char )

Hello EveryOne !!!!
I need Help !!
I am new to Java ,.... I got assignment where i need to Check the String , if that string Contains Any Non Japanse Character ( a~z , A~Z , 0 -9 ) then this should be replaced with Double Byte ( Japanese Char )...
I am using Java 1.2 ..
Please guide me ...
thanks and regards
Maruti Chavan

hello ..
as you all asked Detail requirement here i an pasting C code where 'a' is passed as input character ..after process it is giving me Double Byte Japanese "A" .. i want this to be Done ..using this i am able to Convert APLHA-Numeric from singale byte to Doubel Byte ( Japanse ) ...
Same program i want to Java ... so pleas guide me ..
#include <stdio.h>
int main( int argc, char *argv[] )
char c[2];
char d[3];
strcpy( c, "a" ); // a is input char
d[0] = 0xa3;
d[1] = c[0] + 0x80;
printf( ":%s:\n", c ); // Orginal Single byte char
printf( ":%s:\n", d ); // Converted Double Byte ..
please ..
thax and regards
Maruti Chavan

NLS_LENGTH_SEMENTICS from BYTE TO CHAR

Hi,
For supporting multibyte character, we need to change NLS_LENGTH_SEMENTICS parameter from BYTE to CHAR. But this parameter setting will effect for new database tables created thereafter. To change the storage characteristics for existing database tables we explicitly executed Alter statements for database tables for columns having datatype as Varchar2 and Char.
Problem:
======
Since the number of database tables in PRODUCTION are very high and contains approx. 600 million of records spread over 400 database tables, we are not in a position to afford the time which will be spent in altering these database tables in PRODUCTION.
We ran the test by alter script in System Test environment and alteration of database tables covering 150 tables and 200 million of records was carried out in almost 16-20 hrs.
APPROACHES WE HAVE IN MIND
==========================
1. Alter all the table columns (We tried the same and taking too much time)
2. Export /Import with NLS_LENGTH_SEMENTICS set as CHAR(We discuss with our DBA about this approach and found that it will also take too much time and there is RISK of data inconsistency)
3. Drop the index of the table, run alter script for changing storage type BYTE to CHAR , and rebuild the index (this is also taking too much time).
All above approaches are very costly in terms of time, that we cannot afford.
If any one having better solution then please suggest.
thanks in advance
Syed

Hi
We are also facing a similar problem
We ran alter table scripts and now compiling the objects
and that is taking lot of time.
we have around 4000 invalids that by parallel recomp came down to 2000 but still these 2000 which are mostly packages .. are giving a hard time.
if anyone has faced/found a similar issue/solution pls post. or maildirectly to me.
Sunil Choudhary

Change NLS_LENGTH_SEMANTICS from BYTE to CHAR on Oracle 9i2 problem!

Hi,
I have created a new database on Oracle 9i 2, I did not find the correct pfile parameter for the NLS_LENGTH_SEMANTICS setting.
So have created a standart UTF8 database and now I am trying to change the standard NLS_LENGTH_SEMANTICS=BYTE to CHAR. When I execute the following command in SQL PLUS "ALTER SYSTEM SET NLS_LENGTH_SEMANTICS=CHAR SCOPE=BOTH"
The system is tells me that command is successfully executed.
But when I look at the NLS_DATABASE_PARAMETERS table I do not see any change for the NLS_LENGTH_SEMANTICS parameter.
I have also restarted the instance but still everything is the same as it was before.
Do you know what I am doing wrong?
Regards
RobH

Hi,
Yeah you are right, the nls_session_parameters "NLS_LENGTH_SEMANTICS" for the app user is set to CHAR.
This means that NLS_DATABASE_PARAMETERS is from the SYS or SYSTEM user view?
Thanks a lot
Regards
RobH

Using bytes or chars for String phonetic algorithm?

Hi all. I'm working on a phonetic algorithm, much like Soundex.
Basically the program receives a String, read it either char by char or by chunks of chars, and returns its phonetic version.
The question is which method is better work on this, treating each String "letter" as a char or as a byte?
For example, let's assume one of the rules is to remove every repeated character (e.g., "jagged" becomes "jaged"). Currently this is done as follows:
public final String removeRepeated(String s){
                char[] schar=s.toCharArray();
          StringBuffer sb =new StringBuffer();
          int lastIndex=s.length()-1;
          for(int i=0;i<lastIndex;i++){
               if(schar!=schar[i+1]){
                    sb.append(schar[++i]);//due to increment it wont work for 3+ repetions e.g. jaggged -> jagged
          sb.append(schar[lastIndex]);
          return sb.toString();
Would there be any improvement in this computation:public final String removeRepeated(String s){
          byte[] sbyte=s.getBytes();
          int lastIndex=s.length()-1;
          for(int i=0;i<lastIndex;i++){
               if(sbyte[i]==sbyte[i+1]){
                    sbyte[++i]=32; //the " " String
          return new String(sbyte).replace(" ","");
Well, in case there isn't much improvement from the short(16-bit) to the byte (8-bit) computation, I would very much appreciate if anyone could explain to me how a 32-bit/64-bit processor handles such kind of data so that it makes no difference to work with either short/byte in this case.

You may already know that getBytes() converts the string to a byte array according to the system default encoding, so the result can be different depending on which platform you're running the code on. If the encoding happens to be UTF-8, a single character can be converted to a sequence of up to four bytes. You can specify a single-byte encoding like ISO-8859-1 using the getBytes(String) method, but then you're limited to using characters that can be handled by that encoding. As long as the text contains only ASCII characters you can get away with treating bytes and characters as interchangeable, but it could turn around and bite you later.
Your purpose in using bytes is to make the program more efficient, but I don't think it's worth the effort. First, you'll be constantly converting between {color:#000080}byte{color}s and {color:#000080}char{color}s, which will wipe out much of your efficiency gain. Second, when you do comparisons and arithmetic on {color:#000080}byte{color}s, they tend to get promoted to {color:#000080}int{color}s, so you'll be constantly casting them back to {color:#000080}byte{color}s, but you have to watch for values changing as the JVM tries to preserve their signs.
In short, converting the text to bytes is not going to do anywhere near enough good to justify the extra work it entails. I recommend you leave the text in the form of {color:#000080}char{color}s and concentrate on minimizing the number of passes you make over it.

Byte to Chars converter

Hi,
I'm looking for a converter from byte array to char for different encodings (ANSI, UTF-8 and UTF-16BE, UTF-16LE encodings).
I strongly believe there is a library/class that can do this.
Thanks in advance.
Lubos

Well the problem is that I have to count the number of bytes and look for a special characters (like Form Feed).
The only possibility I've found is to write my own parser..
I've tried the InputStreamReader and implement my own implementation of InputStream for counting the bytes, but it seems the method read(byte[]) is not called every time..

How to find out if colums is defined as VARCHAR2 in bytes or char?

Hello,
I'd like to know if it is possible to find out if a colum table (or view) is defined as a VARCHAR2 in bytes or in CHAR on Oracle 10g.
When I do a desc, it shows only VARCHAR2 with its length but not if it is bytes or char. How can I know for sure?
Thanks,

SQL> create table t
id    varchar2 (10 char),
id2   varchar2 (10 byte)
Table created.
SQL> select column_name, data_type, char_used
from cols
where table_name = 'T'
COLUMN_NAME                                   DATA_TYPE       CHAR_USED
ID                                            VARCHAR2        C
ID2                                           VARCHAR2        B
2 rows selected.

Trying to understand the details of converting an int to a byte[] and back

I found the following code to convert ints into bytes and wanted to understand it better:
public static final byte[] intToByteArray(int value) {
return new byte[]{
(byte)(value >>> 24), (byte)(value >> 16 & 0xff), (byte)(value >> 8 & 0xff), (byte)(value & 0xff) };
}I understand that an int requires 4 bytes and that each byte allows for a power of 8. But, sadly, I can't figure out how to directly translate the code above? Can someone recommend a site that explains the following:
1. >>> and >>
2. Oxff.
3. Masks vs. casts.
thanks so much.

By the way, people often introduce this redundancy (as in your example above):
(byte)(i >> 8 & 0xFF)When this suffices:
(byte)(i >> 8)Since by [JLS 5.1.3|http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#25363] :
A narrowing conversion of a signed integer to an integral type T simply discards all but the n lowest order bits, where n is the number of bits used to represent type T.Casting to a byte is merely keeping only the lower order 8 bits, and (anything & 0xFF) is simply clearing all but the lower order 8 bits. So it's redundant. Or I could just show you the more simple proof: try absolutely every value of int as an input and see if they ever differ:
   public static void main(String[] args) {
      for ( int i = Integer.MIN_VALUE;; i++ ) {
         if ( i % 100000000 == 0 ) {
            //report progress
            System.out.println("i=" + i);
         if ( (byte)(i >> 8 & 0xff) != (byte)(i >> 8) ) {
            System.out.println("ANOMOLY: " + i);
         if ( i == Integer.MAX_VALUE ) {
            break;
   }Needless to say, they don't ever differ. Where masking does matter is when you're widening (say from a byte to an int):
   public static void main(String[] args) {
      byte b = -1;
      int i = b;
      int j = b & 0xFF;
      System.out.println("i: " + i + " j: " + j);
   }That's because bytes are signed, and when you widen a signed negative integer to a wider integer, you get 1s in the higher bits, not 0s due to sign-extension. See [http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#5.1.2]
Edited by: endasil on 3-Dec-2009 4:53 PM

I pull fiftyfour bytes of data from MicroProcessor's EEPROM using serial port. It works fine. I then send a request for 512 bytes and my "read" goes into loop condition, no bytes are delivered and system is lost

I pull fiftyfour bytes of data from MicroProcessor's EEPROM using serial port. It works fine. I then send a request for 512 bytes and my "read" goes into loop condition, no bytes are delivered and system is lost

Hello,
You mention that you send a string to the microprocessor that tells it how many bytes to send. Instead of requesting 512 bytes, try reading 10 times and only requesting about 50 bytes at a time.
If that doesn�t help, try directly communicating with your microprocessor through HyperTerminal. If you are not on a Windows system, please let me know. Also, if you are using an NI serial board instead of your computer�s serial port, let me know.
In Windows XP, go to Start, Programs, Accessories, Communications, and select HyperTerminal.
Enter a name for the connection and click OK.
In the next pop-up dialog, choose the COM port you are using to communicate with your device and click OK.
In the final pop
-up dialog, set the communication settings for communicating with your device.
Type the same commands you sent through LabVIEW and observe if you can receive the first 54 bytes you mention. Also observe if data is returned from your 512 byte request or if HyperTerminal just waits.
If you do not receive the 512 byte request through HyperTerminal, your microprocessor is unable to communicate with your computer at a low level. LabVIEW uses the same Windows DLLs as HyperTerminal for serial communication. Double check the instrument user manual for any additional information that may be necessary to communicate.
Please let me know the results from the above test in HyperTerminal. We can then proceed from there.
Grant M.
National Instruments

Convert.ToByte and logical masks, from VB to LabVIEW

Hi guys,
I have to write a VI communicating via RS232 with a microcontroller for a PWM application. A colleague has given me the GUI he has developpd in VB and I would like to integrate it into my LabVIEW programme by converting the VB code into Labview code. Here's the code:
Private Sub LoadButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles loadButton.Click
        Dim bufLen As Integer = 12      // Buffer length
        Dim freq As Integer = 0      // frequency
        Dim pWidth As Integer = 0      // pulse width
        Dim dac As Integer = 0       // Value used in oscillator setting for generating pulse frequency
        Dim addr As Integer = 0      // Address of the pulse width in the pulse generator.
        Dim rTime As Integer = 0      // duration of machining/pulse train in ms.
        Dim returnValue As Byte = 0      // A variable for storing the value returned by the
//microcontroller after it receives some data
        Dim buffer(bufLen) As Byte       // creates an array of bytes with 12 cells => buffer size = 8 x12 = 96 bits
// can you explain a bit please I know you're converting the entered values into byte and put them one by one in a specific order. This order is how the
//microcontroller expects them
            addr = (Floor((pWidth - Tinh) / Tinc)) // Formula from hardware, calculates address setting for pulse generator to set pulse width.
            buffer(0) = Convert.ToByte(Floor(3.322 * (Log10(freq / 1039)))) // Caluclates OCT value for use in setting oscillator for pulse freq.
            dac = (Round(2048 - ((2078 * (2 ^ (10 + buffer(0)))) / freq))) // Calculates DAC value for use in setting oscillator for pulse freq.
            buffer(1) = Convert.ToByte((dac And &HF00) >> 8)                         //
// &H is the vb.net to tell it its hex code, F00 gives the top 4 bits from a 12 bit value.
            buffer(2) = Convert.ToByte(dac And &HFF) // For values that are larger than 256 (8bits) the value needs to be split across 2 bytes (16 bits) this gets the //bottom 8 bits. &H is the vb.net to tell it its Hex.
            buffer(3) = Convert.ToByte((addr And &HFF0000) >> 16) // This value may be so large it requires 3 bytes (24bits). This gets the top 8 bits.
            buffer(4) = Convert.ToByte((addr And &HFF00) >> 8) // This gets the middle 8 bits.
            buffer(5) = Convert.ToByte(addr And &HFF)// This gets the bottom 8 bits.
            buffer(6) = Convert.ToByte((rTime And &HFF0000) >> 16) //This value may also be 3 bytes long.
            buffer(7) = Convert.ToByte((rTime And &HFF00) >> 8)
            buffer(8) = Convert.ToByte(rTime And &HFF)
            buffer(9) = Convert.ToByte(2.56 * ocpBox.Value) // The ocp pulse period is formed of 256 steps or counts, so if a percentage is requested, this formula gives the number of steps/counts required to set the pulse width
            buffer(10) = Convert.ToByte(tempBox.Value)
            If (tempCheck.Checked = True) Then
                buffer(11) = 1
            Else
                buffer(11) = 0
            End If
            freq = ((2 ^ buffer(0)) * (2078 / (2 - (dac / 1024))))
            pWidth = Tinh + ((((Convert.ToInt32(buffer(3))) << 16) Or ((Convert.ToInt32(buffer(4))) << 8) Or (Convert.ToInt32(buffer(5)))) * Tinc)
            ' Connect to device
            serialPort1.Write(1) // Sends the number 1. This tells the microcontroller we are about to start sending data. It should respond with a zero if it is ready
//and the connection is good.
The line "serialPort1.Write(buffer, 0, bufLen)" sends the buffered data where the variables are: buffer = the buffered data; 0 = the position in the buffer to start from; bufLen = the position in the buffer to stop sending data.
What's the best way to deal with the Convert.ToBytes and the logical masks And ??
Thanks in advance for your time and consideration,
regards
Alex
Solved!
Go to Solution.

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Byte or CHAR? - as Unit

Hi all,
DB - 9.2
Which is the better option to keep unit as Byte or CHAR while using the VARCHAR2 datatype?
Suppose unit is selected as Byte then is it not cumbersome to calculate the max. no. of characters could be stored in the field?

Hi!
I'd propose CHAR, because with BYTE it is dependent of the character set how many characters you can store in your field. This means -> calculate :)
Best regards,
Daniel

Link between documentation for chars value and chars

Hi,
we need to find out sap transaction or report for link between documentation of chars value and chars.
we know for specific chars through CT04 and going to VALUES sub-tab then selecting perticular chars value and clicking on the documentation for value.

Go to transaction CT10 and select display option 'Allowed values'. You will have the characteristics along with their values.

Byte and char !!!

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