Is there an advantage in using byte instead of int beyond the space savings? In my program, I'll never need close to the max value of a byte, let alone int, so it seems like a waste to make my primitives ints.
I need to send a byte array across a network. I know how to do this. (server->client)
byte[] myArray = new byte[]{0,1,2,3,4,5,6,7,8,9}; DataOutputStream.write(myArray);
... and I know how to receive it.
byte[] myArray = new byte[10]; DataInputStream.read(myArray);
When I send over one of these arrays, it ends up stopping storing values in the array when only about half the array is received, even though the array is sent from the server all at once. This results in the receiver's array, in this case, being something like {1,2,3,4,0,0,0,0,0,0}.
I can easily solve this - and already have - by simply adding a loop onto it and waiting for the bytes to all be received, as the method returns the amount of bytes actually read.
I am simply wondering if there is a better solution to this, as the current solution isn't that elegant. Did I do something wrong to cause only a part of the array to be sent first? Would it be better to use DataInputStream.readByte() to read off the bytes one by one rather than an array at once, and then store them in an array afterward? Would this cause a performance decrease as each byte is read individually? (I'm sending an array of several million bytes)
I am new to Android. I have byte array of size 10. I am passing the Decimal values (131 - 140) to byte array. But while printing I get Negative (-) values with decreasing order .
How can I get same value as positive values?
Or How can I store positive value e.g. 131 as byte array element.
Please not my requirement is array must be ByteArray only
I have a checksum function that is suppose to read IPV4 packet and return a short integer value. The IPV4 packets are stored in a byte array. I am having trouble storing the first 8 bits and second 8 bits of the short integer into the byte arrays especially when they have leading 1s. For example, if my checksum returns 5571 (binary = 0001 0101 1100 0011) The first 8 bits is suppose to represent 195 but when I try to assign a larger integer type to a btye the information gets sign extended. The 195 turns into -61. I tried using bit addition like array[10] = array[10] & 0xff, but the result remains the same.
public static short checksum(byte [] a, int length) { short sum = 0; long data; int i = 0; while(length > 1) { data = (((a[i] << 8) & 0xff00) | ((a[i + 1]) & 0xff)); sum += data;
I am reading a book on Java and we are at a point where it is explaining type conversion in expressions. One of the examples shared has a byte being multiplied by itself and then assigned back to itself ...
byte b; b = 10; b = (byte) (b * b);
this is all good and dandy (that is, the code functions properly).
However, I am confused why I need to typecast here! Without the cast, the compiler screams, "Type mismatch: cannot convert from int to byte." Yet I haven't converted to an int?? It appears there was an implicit conversion.
The final value, 100, is clearly within byte's range of -127 to +127 isn't it? So I am lost as to what is the issue here.
I'm trying to create Web Services with Eclipse (Java Runtime 7 (also tried 8) Tomcat 7 (also tried 8).Web Service with parameter "byte[]" and return value "byte[]" works fine.Web Service with parameter "myOwnClass" and return value "myOwnClass" works also fine.But if I have a "byte[]" element in "myOwnClass" and I run my Client test program I get the following error:
AxisFault faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException faultSubcode: faultString: java.lang.NumberFormatException: For input string: "MTExMTExMTExMQ=="
Why? I don't have any numeric element (such as int ...) in my class members!?
I have a msg object that contains an ArrayList<Integer> collection. However, in order to send the elements in the array over the udp socket, it needs to be sent as a byte[] array. So why am I using ArrayList<Integer> over byte array in first place? Well when I receive data from socket from embedded c program, I need to get an unsigned representation of the data, and thus I need to store it in integers, since bytes in Java are unsigned and unsigned chars in c that are greater than 127 will yield incorrect values in java. But when I send an ack back over the socket, I need to send the data back as bytes. So I convert the ArrayList<Integer> to a byte array:
Java Code: byte[] data = msg.toByteArray(); DatagramPacket response = new DatagramPacket(data, data.length, packet.getAddress(), packet.getPort()); public class Gprs { ... public byte[] toByteArray(){
[Code] ....
The problem is I get an "Cannot cast from Integer to byte" when trying to cast the integer to byte: data[i] = (byte)m_data.get(i);
okay so it says that java int short and byte variables are the same thing. They take whole numbers. But what is the point of byte and short to even exist if int covers it all? Is the short and byte just for fun?
byte b = 100; it works (implicit conversion of implicit int literal 100 to byte.
But if you have a methodvoid bla(byte b){}
And want to invoke it with a literal (which is an int by default):bla(8) then there is no implicit conversion.
Is the byte b = 100; just an exception in Java? And is it the rule that one has to explicitely cast (narrow) integer literals when passing to smaller-than-int types?
I've a small question relating to type promotion I can't find an answer for on the web. Basically in your code if you have :
byte b = 0; b = b + 1;
The compiler will complain about the result being an int which cannot be assigned to a byte. That I understand, as b on the right hand side of the expression is promoted to an int and the result of the addition is an int. However the following does compile :
byte b = 0; b++;
Does the post increment not carry out the post increment as "give me the value of b and then add 1 to b" where I would have expected 'add 1 to b' to do the same integer promotion as the previous example ? The compiler will also allow the following
I'm trying to save a picture from byte arrays using RandomAccessFile. The file appears but doesn't open (like its corrupted).
I'm using the bittorent protocol which gives a SHA-1 hash that I compare all the bytes with to verify the data. All the bytes pass the hash check and all the hashes are checked. So I'm pretty sure I'm getting all the bytes correctly.
Is there anything I can do that could tell what's going wrong?
public RUBTClient(final TorrentInfo2 tInfo, final String outFileName) { ... this.outFileName = outFileName; File destined = new File(outFileName); try { destined_file = new RandomAccessFile(destined, "rw"); destined_file.setLength(tInfo.file_length); } catch (FileNotFoundException e1) {
I and a friend are working with a project to create a file system, who manages a secondary memory simulated as a byte array in Java. We want the file system to be a hierarchical tree structure like in UNIX.
We have come quite far, but the paths are not handled correct. I seem to have mistaken the relative folder ./ for the root folder, but it should mean "working directory folder", ie, where I stand now. That is, if I stand in /dir1 as my "working directory" and make mkdir ./dir2 then should dir2 end up as subfolder in dir1. But with me it appears in the root.
I am trying to write a specific byte sequence to a specific memory location on a removable storage drive. Does Java allow me a way to do this? I know the dangers in accessing memory, but the memory location of the data that will be written will never change.
my first assignment is to convert a md5 string to password of the user, the MD5 function is available, i just need to call it and print the result. Here is my code. I can't call the md5 because of the String[] and String is different in main and md5 function,modify the code so it can run properly, also the input has to be entered from command line.
import java.security.*; public class PasswordCracker { public static void main (String[] args){ String password; md5(args) System.out.printf(""+password+"");
I'm trying to create a booklist in java using swings but I'm facing a problem. I don't know how to add a search function to my list. I need a search box with the book names.
where I have to write a Java program that asks for user input regarding a book and provides information based on that input like the number of pages required, number of words on the final page and if the final page is more than half full, etc. We are told that each page should have 250 words maximum to use for our calculations. The problem I am having here is that when the total number of words is a multiple of 250 the output tells me that there are 0 words on the last page when in fact there are 250. I've tried messing around with mod functions in this format ((x+a)%250)+y which is what the professor told us to use instead of creating an if-statement for this case but I haven't been able to crack it. I don't think I fully understand how the mod function cycle could work for this case.
import javax.swing.JOptionPane; public class CorreiaFranciscaA1Q1 { public static void main(String[] args) { String ManuscriptTitle = JOptionPane.showInputDialog ("Please enter a book title."); String AuthorName = JOptionPane.showInputDialog ("Please enter the author name."); String TotalWords = JOptionPane.showInputDialog ("Please enter the number of words.");
[code]....
Above if totalWords is a multiple of 250 like 17500 then wordsFinalPage will give us 0 and I need it to give 250. How can I do that without using an if statement but instead using a mod function?
Using JPA 2.1, I have been trying without luck to call a function that returns a REF CURSOR containing RECORD TYPES. Is there a way of doing this?
One Example of trying:
Query query = em.createNativeQuery("select my_package.my_function from dual"); Object a = query.getSingleResult();
I have also tried to use the StoredProcedureQuery though this does not look like it can return the functions value.
Produced
org.springframework.orm.jpa.JpaSystemException: No Dialect mapping for JDBC type: -10; nested exception is org.hibernate.MappingException: No Dialect mapping for JDBC type: -10 at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:244)
