Java ObjectInputStream throws EOFException while reading a primitive

Question

I'm having hard times understanding the behaviour of Output/Input streams in Java.

ObjectOutputStream implements DataOutput interface so, as DataOutputStream, it has the methods to write primitives.

But reversing the written bytes ObjectInputStream throws EOF.

    byte array[]=new byte[50];
    byte value=2;
    System.out.println(value); //prints 2


    ByteArrayOutputStream os=new ByteArrayOutputStream();
    ObjectOutputStream oss=new ObjectOutputStream(os);
    oss.writeByte(value);

    array = os.toByteArray();

    //get back the original value from the byte array
    ObjectInputStream ois=new ObjectInputStream(new ByteArrayInputStream(array));
    byte result=ois.readByte(); // -> throws EOF Exception (see below)

    System.out.println("Result -> "+result);

Throws this Exception

Exception in thread "main" java.io.EOFException
    at java.io.DataInputStream.readInt(DataInputStream.java:392)
    at java.io.ObjectInputStream$BlockDataInputStream.readInt(ObjectInputStream.java:2827)
    at java.io.ObjectInputStream.readInt(ObjectInputStream.java:971)
    at z.reti.TestOOS.main(TestOOS.java:21)

Same Exception is thrown using other primitives. Replacing the primitive byte with the Byte wrapper class (and using Read/WriteObject) the problem is gone...

Is there a way to use ObjectOutputStream and ObjectInputStream with primitives?

semperfids · Accepted Answer · 2016-01-06 17:16:27Z

2

You are not closing your ObjectOutputStream. Just add oss.close() after you do oss.writeByte(value) and your program should work as expected.

answered Jan 6, 2016 at 17:16

semperfids

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2 Comments

Z856 Over a year ago

that's correct. Why using writeObject the problem didn't appear?

Titus Over a year ago

@Z856 Probably because the stream is flushed in that case

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