byte b; // ... int i = b & 0xff;
To get the effect of a 16bit unsigned use char.
To get the effect of a 32bit unsigned:
int i; // ... long l = i & 0xffffffffL;If you have an extensive amount of unsigned work to do, especially 64bit 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 64bit unsigned, consider that addition and subtraction give you the same results whether you consider the operands signed or unsigned. When you multiply two unsigned 64bit operands together you get a 128bit result which won’t fit in a long anyway, so 64bit unsigned multiply is not useful. To implement an unsigned 64bit 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  8bit  16bit  32bit  64bit  
=  load  
=  store  
+  addition/subtraction  
*  multiplication  
/  division  
%  remainder  
== !=  equality  
< <= > >=  comparison  
&  ~ !  bitwise  
>>> >> <<  shift 
For large unsigned numbers, look into BigInteger and a BigDecimal.
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.common18.ST.toLZHexString and com.mindprod.common18.ST.toHexString might be useful.
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:
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