Java read write binary file

I don't see that mentioned in the initial post, but assuming that is the case as it would get much more complex if the header has optional args and different sizes. Once you have the info, there can be a header class in which you assign the contents of the buffer that you've already read. And then parse the records in a similar fashion. As other people mention DataInputStream and Buffers are probably the low-level API's you are after for dealing with binary data in java.

I don't know of any Java versions off hand, but taking that approach declaratively specifying the struct in code would probably be the right way to go. With a suitable fluent interface in Java it would probably be quite similar to a DSL. Which might be the kind of thing you are looking for. I have no idea whether it works or is any good, but it looks like a sensible place to start. I would create an object that wraps around a ByteBuffer representation of the data and provide getters to read directly from the buffer.

In this way, you avoid copying data from the buffer to primitive types. Furthermore, you could use a MappedByteBuffer to get the byte buffer. If your binary data is complex, you can model it using classes and give each class a sliced version of your buffer. Also useful are the methods for reading unsigned values from byte buffers. I've written up a technique to do this sort of thing in java - similar to the old C-like idiom of reading bit-fields. Note it is just a start but could be expanded upon.

In the past I used DataInputStream to read data of arbitrary types in a specified order. As of 1. Buffer family might be the way to go, but it seems that the your code might actually be more complicated. These classes do have support for handling endian issues.

A while ago I found this article on using reflection and parsing to read binary data. In this case, the author is using reflection to read the java binary. But if you are reading the data into a class file, it may be of some help.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Active 7 years ago. Viewed 2k times. Improve this question. What's the 'rubbish' you're seeing? Do you realize that 10 is "ten million onehundredandonethousand and ten"?

Add a comment. Active Oldest Votes. Improve this answer. As i say to newbiedoodle what can i do in order to write this binary code and to just be this Yes but with Filewriter every zero and one will be counted as byte and not as bit.. Panagiotis You can't have it both ways. Either you save it as binary and you can't read it as text or you save it as text. And by the way the actual file size ie actual space taken up on your HD is likely to be the same anyway due to the way file tables work unless you're saving thousands of numbers — ControlAltDel.

For the actual size yes you are right I have a table which contains paths for each letter.. If you want to directly read the binary as a String and you don't need to do manipulation, use a FileWriter.

If you want to write binary numbers, prefix the number with 0b or write the decimal equivalent, so the compiler reads it in binary. Show 4 more comments. Nic Nic 5, 8 8 gold badges 47 47 silver badges 66 66 bronze badges.

So what can i do in order to write this binary code and to just be this Panagiotis I have answered this — ControlAltDel. Community Bot 1 1 1 silver badge. Panagiotis Whoops.

Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses. Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked 0. Related Hot Network Questions. That is, we start with two questions:. And we find the answers to these by searching through the java. Because we are performing binary output, we need to use some subclass of OutputStream.

This class has the right kind of constructors, but it only contains write methods for writing int s and byte s, and we need to be able to write String s and double s as well as int s. These kinds of methods are found in DataOutputStream Fig.

However, note that the writeChar takes an int parameter, which indicates that the character is written in binary format rather than as a ASCII or Unicode character. To construct a stream to use in writing employee records, we want to join together a DataOutputStream and a FileOutputStream.

This enables the program to write data to the DataOutputStream , which will pass them through the FileOutputStream to the file itself. That settles the first question. To develop the output algorithm, we need some kind of loop that involves calls to the appropriate methods.

In this case, because we are generating random data, we can use a simple for loop to generate, say, five records of employee data. We need one write statement for each of the elements in the employee record: The name String , age int , and pay rate double :. Within the loop body we have one output statement for each data element in the record. The names of the methods reflect the type of data they write. Thus, we use writeInt to write an int and writeDouble to write a double. There is no DataOutputStream.

Instead, String s are written using the writeUTF method.