Getting bytes from an image file is not different from getting bytes from an arbitrary file. Would you please help me to write a code to read the data in the following formats: First format for example, separated by lines : store one column of the data in one array 11. Hi, How do I read file into byte array? In that model, there are many files to read. What I don't see is: 1 any use of the array inside your loops. Using the same approach as the community wiki answer, but cleaner and compiling out of the box preferred approach if you don't want to import Apache Commons libs, e. Sorry, but this answer is nonsense. InputStream class which provides the methods for reading from the input stream.
Cool, il try that so. The User class is not difficult to make surely you've done classes before? Here it's casted to an integer. Basically, you've got all the pieces there - why haven't you put them all together? I see you reading data just fine with a loop involving your scanner. If you're trying to create an in-memory file that can be referred to using a File object, you aren't going to be able to do that, either, as explained in , , and many other places. Is the code below good enough? Following line of code can be used: insputStream. Please use code tags when posting code. Note that this approach works whether you can tell the length of your input or not - assuming you have enough memory, of course.
I have a web server which will read large binary files several megabytes into byte arrays. So below code can also be used to convert byte array to String in java. The file starts like this: 1 1 1 881250949 1 2 5 881250949 1 4 2 881250949 ect Why not have a User class with user id and Map as attributes. Then I would like to write the two arrays from the first format to one file with two columns first column for first array and second column for second array. What if the return value is bigger than a maximum integer? So you might be able to read the file all at once, but the underlying hardware is still the deciding factor. You may also find a regular ByteBuffer to be useful, using FileChannel's read ByteBuffer method. File to a byte array and then convert a byte array back to a java.
Help is always available here. Sometimes it becomes necessary to read a file into byte array for certain type of business processing. Basically, you've got all the pieces there - why haven't you put them all together? Through clever use of file. I would not label my own solutions with such a statement. If there's any line you don't ubderstand there you might as well ask Thanks so much for your help.
Help is always available here. Second format for example, separated by spaces : store one column of the data in one array, so there are three arrays 1. To the binary file into byte array we will use the class InputStream of java. All you have to do is to create either a ByteArrayOutputStream or CharArrayWriter, and write your data to it, as you would to any other stream or writer. That is especially important when you have multiple parallel operations as suggested by the question to minimise system load and maximise throughput. It seems there are problems in declaration of dataArray3, calling method readFile2 and in the method itself.
You need to stay up to date with that library, include the dependency in your build scripting etc, communicate it to people using your code etc etc. Means, an ArrayList having 10 elements, if you are inserting at index 5, then you need to shift the indexes above 5 to one more. Using the same approach as the community wiki answer, but cleaner and compiling out of the box preferred approach if you don't want to import Apache Commons libs, e. ReadAllBytes , since I saw in the comments on the top response that includes. As always a simple sample program to profile which is fastest will be most beneficial.
There are times when we need to read file content into a byte array like when we need to send the file content over the network or we need to calculate check sum using file data. Here is the complete code of the program: import java. ComputeHash fs ; return hash; } }. This method reads repeatedly from the file until the requested number of bytes are read. Observe that variable count is never used. What if the return value is bigger than a maximum integer? What I don't see is: 1 any use of the array inside your loops. But insertion and deletion is much faster with LinkedList, because if you know the node, just change the pointers before or after nodes.
All your second set of loops does is increment i and j. Object You have to type cast the elements from the ArrayList to doubles like. When while loop is first time executed, offset is 0, and length is the length of the file, and, becaouse zero is, should be in some case, less then a length of the file, the loop starts to be executed. That's all for this topic How to Convert a File to Byte Array - Java Program. It executes only once, and only once. This approach is clumsy and would only be necessary when you're actually interested in manipulating the image in some way resizing, cropping, colorizing, etc. Browse other questions tagged or.
The file starts like this: 1 1 1 881250949 1 2 5 881250949 1 4 2 881250949 ect I'm not sure how to put them together. What if the return value is bigger than a maximum integer? What I want is to convert java. We can also get the byte array using below code. I'd rather have some extra lines of code than yet another dependency. You cannot do it for File, which is primarily an intelligent file path. There are times when we need to read file content into a byte array like when we need to send the file content over the network or we need to calculate check sum using file data.