String to byte conversion

Question

How can I convert a string to byte? For example, Byte.parseByte("255"); causes NumberFormatException since (for some weird reason) byte is signed in java so the maximum value it can have is 127.

So I need a function such that

public static byte toByte(String input) {
...
}

And for example toByte("255"); should return -1(ie bits: 11111111)

Something like implementation of 2s complement

"for some weird reason byte is signed". As opposed to it being unsigned for some weird reason? — DJClayworth, Dec 20 '11 at 14:09
Its unsiged in c,c++,delphi,c#,... I think it doesnt make sense because byte is used mainly for binary data so should have no sign. If there is a need for memory-space-efficient number then there is `short` — Caner, Dec 20 '11 at 14:17
Yea, not including an unsigned byte type is one of the mysteries that eludes me in Java. — Perception, Dec 20 '11 at 14:22
A very similar question has been asked before and several good answers were provided. See: ["What is the best way to work around the fact that ALL Java bytes are signed?"](http://stackoverflow.com/questions/11088/what-is-the-best-way-to-work-around-the-fact-that-all-java-bytes-are-signed) — Jason Braucht, Jan 06 '12 at 15:11

score 8 · Accepted Answer · answered Dec 20 '11 at 14:04

8

Use Integer.parseInt("255") and cast the resulting int to a byte:

byte value = (byte)Integer.parseInt("255");

answered Dec 20 '11 at 14:04

Jesper

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2

Dam my timid nature! that should be my answer! – thecoshman Dec 20 '11 at 14:25

score 1 · Answer 2 · edited May 31 '15 at 08:07

1

   public static void main(String[] args) {    
     String s = "65";
     byte b = Byte.valueOf(s);
     System.out.println(b);

     // Causes a NumberFormatException since the value is out of range
     System.out.println(Byte.valueOf("129"));
  }

edited May 31 '15 at 08:07

mpromonet

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answered May 29 '15 at 19:21

Abdullah Babu Kalam

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score 1 · Answer 3 · answered May 29 '15 at 19:29

1

byte value = (byte)Integer.parseInt("255");

answered May 29 '15 at 19:29

Richard Ayoade

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3

score 0 · Answer 4 · answered Dec 20 '11 at 14:15

I am thinking of the following implementation!

public static byte toByte(String input) {
    Integer value = new Integer(input);

    // Can be removed if no range checking needed.
    // Modify if different range need to be checked.
    if (value > 255 || value < 0)
        throw new NumberFormatException("Invalid number");

    return value.byteValue();
}

String to byte conversion

4 Answers4