Unsigned byte in Java

Java does not have unsigned data types. Your options are:

• Use a wider datatype such as short, char or int
• Use a byte and “manually” interpret it as unsigned (described below)

An unsigned byte

A byte is always signed in Java, but nothing prevents you from viewing a byte simply as 8 bits and interpret those bits as a value between 0 and 255.

Keep in mind that there’s nothing you can do to force your interpretation upon someone else’s method. If a method accepts a byte, then that method accepts a value between −128 and 127 unless explicitly stated otherwise.

Here are a couple of useful conversions / manipulations.

Printing an unsigned byte

Use Byte.toUnsignedInt and print the resulting int:

byte b = (byte) 0b10010110; // -106 signed, or 150 unsigned

System.out.println("Value of my unsigned byte: " + Byte.toUnsignedInt(b));  // 150

Converting from int to unsigned byte

Casting to byte throws away all but the lowest 8 bits.

int i = 150;        // 00000000 00000000 00000000 10010110
byte b = (byte) i;  //                            10010110

System.out.println(b);                      // -106
System.out.println(Byte.toUnsignedInt(b));  //  150

Converting from unsigned byte to int

Use Byte.toUnsignedInt to avoid sign extension.

byte b = (byte) 0b10010110;           // -106 or 150

int signed = b;                       // -106 (with sign extension)
int unsigned = Byte.toUnsignedInt(b); //  150 (without sign extension)

Or, equivalently:

int unsigned = b & 0xff;

Parsing an unsigned byte

byte b = (byte) Integer.parseInt("150");

System.out.println(Byte.toUnsignedInt(b)); // 150

Or, using Guava:

byte b = UnsignedBytes.parseUnsignedByte("150");

Compare unsigned bytes

Convert to int and compare.

int cmp = Integer.compare(Byte.toUnsignedInt(b1), Byte.toUnsignedInt(b2))
// cmp = -1  =>  b1 < b2
// cmp =  0  =>  b1 = b2
// cmp =  1  =>  b1 > b2

Or, using Guava

int cmp = UnsignedBytes.compare(b1, b2);

Arithmetics

The 2-complement representation “just works” for addition, subtraction and multiplication.

// two unsigned bytes
byte b1 = (byte) 200;
byte b2 = (byte) 15;

byte sum  = (byte) (b1 + b2);  // 215
byte diff = (byte) (b1 - b2);  // 185
byte prod = (byte) (b2 * b2);  // 225

Division requires conversion of operands, and then convertion of result back to byte.

byte ratio = (byte) (Byte.toUnsignedInt(b1) / Byte.toUnsignedInt(b2));