unsigned : Java Glossary

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unsigned
in Java bytes, shorts, ints and longs are all considered signed. The only unsigned type is the 16-bit char. To use the sign bit as an additional data bit you have to promote to the next bigger data type with sign extension then mask off the high order bits. i.e. To get the unsigned equivalent of a byte:
byte b;
// ...
int i = b & 0xff;

To get the effect of a 16-bit unsigned use char.

To get the effect of a 32-bit unsigned:

int i;
// ...
long l = i & 0xffffffffL;
If you have an extensive amount of unsigned work to do, especially 64-bit unsigned, you might find the WBEM classes useful.

Here is haw to handle unsigned short:

// combining two unsigned shorts into an unsigned int.
short ush = 4;
short usl = 9999;
int ucombined = ( ush & 0xffff ) << 16 | ( usl & 0xffff );

For 64-bit unsigned, consider that addition and subtraction give you the same results whether you consider the operands signed or unsigned. When you multiply two unsigned 64-bit operands together you get a 128-bit result which won’t fit in a long anyway, so 64-bit unsigned multiply is not useful. To implement an unsigned 64-bit division, you could handle it 32 bits as a time, much the way you handled decimal division in grade 4. Check the signs first, if they are 0 just use ordinary division.

You could store a signed or unsigned number in byte, char, int or long.

Sometimes you get the same result in terms of bits whether you treat quantities as signed or unsigned.

Does Signed/Unsigned Matter?
Operator 8-bit 16-bit 32-bit 64-bit
= load
= store
+- addition/subtraction
* multiplication
/ division
% remainder
== != equality
< <= > >= comparison
& | ~ ! bitwise
>>> >> << shift

For large unsigned numbers, look into BigInteger and a BigDecimal.

Displaying Hex

Java’s Integer.toString interprets the value as unsigned. To display unsigned longs, use  Long.toHexString. Writing a base 10 unsigned converter would be a challenge. You also might find com.mindprod.common17.ST.toLZHexString and com.mindprod.common17.ST.toHexString might be useful.

Gotchas

Working with a mixture of constants and bytes, it is easy to trip up when int constants don’t sign extend and (byte) constants do. Consider this example:

Why?

Learning More

Oracle’s Javadoc on Integer.toHexString : available:
Oracle’s Javadoc on Long.toHexString : available:

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