Reading integer values from binary file using Java

Question

I am trying to write values greater than 256 using DataOupPutStream.write() method. When i try reading the same value using DataInputStream.read() it will return 0. So, i used DataOutputStream.writeInt() and DataInputStream.readInt() methods to write and retrieve values greater than 256 and it is working fine.

Refer the below code snippet i would like to know the behaviour of the compiler as what it does in the in.readInt() inside the while statement.

FileOutputStream fout = new FileOutputStream("T.txt");
BufferedOutputStream buffOut = new BufferedOutputStream(fout);
DataOutputStream out = new DataOutputStream(fout);

Integer output = 0;
out.writeInt(257);
out.writeInt(2);
out.writeInt(2123);
out.writeInt(223);
out.writeInt(2132);
out.close();

FileInputStream fin = new FileInputStream("T.txt");
DataInputStream in = new DataInputStream(fin);

while ((output = in.readInt()) > 0) {
    System.out.println(output);
}

The Output when i ran this snippet is :

Exception in thread "main" java.io.EOFException
    at java.io.DataInputStream.readInt(Unknown Source)
    at compress.DataIOStream.main(DataIOStream.java:34)
257
2
2123
223
2132

But when i ran in debug mode i get the following output :

2123
223
2132
Exception in thread "main" java.io.EOFException
    at java.io.DataInputStream.readInt(Unknown Source)
    at compress.DataIOStream.main(DataIOStream.java:34)

download.oracle.com/javase/6/docs/api/java/io/…

Prince John Wesley
– Prince John Wesley

2011-05-26 08:34:07 +00:00
Commented May 26, 2011 at 8:34 — Prince John Wesley
– Prince John Wesley, Commented May 26, 2011 at 8:34

Peter Lawrey · Accepted Answer · 2011-05-26 08:40:49Z

8

The readInt() method is a method like any other. You are getting an EOFException because that's what the Javadoc for readInt() says will happen when you reach the end of the file.

When I run

DataOutputStream out = new DataOutputStream(new FileOutputStream("T.txt"));
out.writeInt(257);
out.writeInt(2);
out.writeInt(2123);
out.writeInt(223);
out.writeInt(2132);
out.close();

DataInputStream in = new DataInputStream(new FileInputStream("T.txt"));
try {
    while (true) 
        System.out.println(in.readInt());
} catch (EOFException ignored) {
    System.out.println("[EOF]");
}
in.close();

I get this in normal and debug mode.

edited May 26, 2011 at 8:40

answered May 26, 2011 at 8:31

Peter Lawrey

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6 Comments

rozar Over a year ago

Thanks Peter..EOFException is fine. But the results differ in the debug mode and in the run mode.

Peter Lawrey Over a year ago

When you write to System.out and System.err (when exception are written) the order of the output is not consistent/always the same. Using debug is enough to change the order of the output.

rozar Over a year ago

yeah.. But in the Debug mode the values read is also different. Suppose if i remove the while clause in my code snippet and replace with 5 System.out.println(in.readInt());

Peter Lawrey Over a year ago

@rozar, The while clause makes no difference. It is more likely that the debug is correct and you are doing something wrong.

rozar Over a year ago

@Peter, Thanks for your reply and i really appreciate it. Can you find any mistakes in my code snippet above except the EOFexception handling.

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