Though Java can be used in handheld units, when someone talks of a Java calculator, they usually mean a desktop simulator of an electronic handheld calculator. You click the buttons. The simulated calculator has the advantage of a big screen for displaying results, debugging information and graphs. By using double, you can get about 14 significant digits.
You can put mathematical expressions in ordinary Google search boxes and have Google evaluate them for you.
It is highly convenent to have a handheld calculator available when you are programming. You use it to check calculations, interconvert decimal ⇔ hex ⇔ binary ⇔ octal, to interconvert various forms of 24bit colour names, to estimate results, to check your trigonometry with actual examples, interconvert metric ⇔ English/US/Imperial measure… Most calculators do not support the programmers’ functions with buttons, though the advanced ones allow you to download applications to handle base conversion.
$28.95recommend electronic⇒Texas Instruments TI36X Scientific Calculator  
asin  B00000JBNM  

This is solar powered scientific calculator that does the necessary programmer and scientific/mathematical tasks you would want including hex, binary, octal and bitwise logical functions. It is not programmable, though it can do some statistical functions. It calculates accurate to 12 digits and displays up to 10. That will display 32bit ints quantities, but not 64bit longs. It is quite inexpensive, and known for unusual durability. You can read the manual online to learn precisely what it can do. Compare it with its brothers to be sure you have the best fit. Be careful, just because another calculator is more expensive does not mean it has all the same programmer features.  
 
Greyed out stores probably do not have the item in stock 
available on the web at: 
http://mindprod.com/jgloss/calculator.html  
optional Replicator mirror

J:\mindprod\jgloss\calculator.html  
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