Java.Random.IO中的ReadLong和WriteLong方法

Question

I am trying to write Long using Java command for Random File IO as follows:

fstreamOut = new FileOutputStream(new File("C:\\Basmah","dataOutput.7"),true);
DataOutputStream out=new DataOutputStream(fstreamOut);
Long p= Long.parseLong(longNumberInString );  // Number of digits for this long key are 7-15
              out.writeLong(p);                  

The problem is that when I write 7-15 digit number using writeLong ; it writes 8 bytes in file. Then I am trying to read the same record into my program and decode it

Long l=in.readLong();

but I dont get the same number as I wrote ; Instead Iget EOF exception.

Answer 1

A long id 64-bit long. That makes 8 bytes. The DataOutputStream's writeLong method writes the binary representation of the long, not the textual one. Without knowing the code used to read the long value, it's impossible to tell why it doesn't work.

Answer 2

The code given in your example and comment should work. The fact that it doesn't suggests that something else is going on here:

• Maybe the writing and reading is happening on different files.
• Maybe the file being written is not flushed / closed before you attempt to read it.
• Maybe something else is overwriting the file.
• Maybe the snippets of code you have provided are different enough to the real code to make a difference.

In the code that attempts to read the file, print what you get when you call f.length() .