Write input to binaryfile and read it back as int (getting back decimal values)

Question

When writing to a binary file like this:

byte[] content = {1,2,3};
FileOutputStream  output =   new FileOutputStream("data.bin");
DataOutputStream fileName = new DataOutputStream(output);
fileName.writeInt(content.length);
for (int i = 0; i < content.length; i++)
{
fileName.writeInt(content[i]);
System.out.println(content[i]);
}
fileName.close();

When reading it back using FileInputStream/DataInputStream and .readInt() everything is ok. (If i use .skip(4); because the first one seems to contain a value wich is the number of digits written)

However, if the byte[] content is replaced with input using scanner.

java.util.Scanner in = new java.util.Scanner(System.in);
String inputAsString = in.nextLine();
byte[] content = inputAsString.getBytes();

I noticed it is written to the binaryfile in decimal. 1 becomes 49, 2 is 50, 3 is 51 ... My question is how can i read it back to 1, 2, 3 just like the first example with the hardcoded byte array.

Paul Rubel · Accepted Answer · 2012-12-05 15:03:51Z

1

When you read in data from input it's a string. So you're getting ascii/utf-x bytes. So the value you're writing is the byte. You want to turn the input you read into an int:

int toWrite = parseInt(inputAsString);
fileName.writeInt(toWrite);

Note that 51 is ascii value assigned to the character '3'

If you write it out as an int you should be able to read it in as such as well.

answered Dec 5, 2012 at 15:03

Paul Rubel

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1 Comment

Bullen Over a year ago

Thanks Paul! Integer.parseInt(inputAsString);

Yogendra Singh · Accepted Answer · 2012-12-05 16:03:07Z

0

Use in.nextByte() in a loop to read the the entries as byte.

     byte[] bytes = new byte[SIZE];
     int indx = 0;
     while(in.hasNextByte()){
        bytes[indx++] = in.nextByte();
     }

EDIT: If you don't know the size then:

    List<Byte> byteList = new ArrayList<Byte>();
    while(in.hasNextByte()){
       byteList.add(in.nextByte());
    }
    Byte[] bytes = byteList.toArray(new Byte[]{});

edited Dec 5, 2012 at 16:03

answered Dec 5, 2012 at 15:01

Yogendra Singh

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3 Comments

Bullen Over a year ago

Thank you. I guess it is possible to use .length instead of knowing the [SIZE]?

Yogendra Singh Over a year ago

@user1879391: I updated the answer with unknown size reading.

Bullen Over a year ago

Great! Now i have two solutions.

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