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    <p>With the possible exception of "short", which arguably is a bit of a waste of space-- sometimes literally, they're all horses for courses:</p> <ul> <li>Use an <strong>int</strong> when you don't need fractional numbers and you've no reason to use anything else; on most processors/OS configurations, this is the size of number that the machine can deal with most efficiently;</li> <li>Use a <strong>double</strong> when you need fractional numbers and you've no reason to use anything else;</li> <li>Use a <strong>char</strong> when you want to represent a character (or possibly rare cases where you need two-byte unsigned arithmetic);</li> <li>Use a <strong>byte</strong> if either you specifically need to manipulate a <em>signed</em> byte (rare!), or when you need to move around a <em>block</em> of bytes;</li> <li>Use a <strong>boolean</strong> when you need a simple "yes/no" flag;</li> <li>Use a <strong>long</strong> for those occasions where you need a whole number, but where the magnitude could exceed 2 billion (file sizes, time measurements in milliseconds/nanoseconds, in advanced uses for compacting several pieces of data into a single number);</li> <li>Use a <strong>float</strong> for those rare cases where you either (a) are storing a <em>huge number</em> of them and the memory saving is worthwhile, or (b) are performing a <em>massive number of calculations</em>, and can afford the loss in accuracy. For most applications, "float" offers very poor precision, but operations can be twice as fast -- it's worth testing this on your processor, though, to find that it's actually the case! [*]</li> <li>Use a <strong>short</strong> if you really need 2-byte signed arithmetic. There aren't so many cases...</li> </ul> <p>[*] For example, in Hotspot on Pentium architectures, f<a href="http://www.javamex.com/tutorials/math/basic_operations.shtml" rel="noreferrer">loat and double operations generally take exactly the same time</a>, except for division.</p> <p>Don't get too bogged down in the memory usage of these types unless you <em>really</em> understand it. For example:</p> <ul> <li><strong>every object size is rounded to 16 bytes</strong> in Hotspot, so an object with a single byte field will take up precisely the same space as a single object with a long or double field;</li> <li>when passing parameters to a method, <strong>every type takes up 4 or 8 bytes on the stack</strong>: you won't save anything by changing a method parameter from, say, an int to a short! (I've seen people do this...)</li> </ul> <p>Obviously, there are certain API calls (e.g. various calls for non-CPU intensive tasks that for some reason take floats) where you just have to pass it the type that it asks for...!</p> <p>Note that String isn't a primitive type, so it doesn't really belong in this list.</p>
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    1. POWhat is the purpose of long, double, byte, char in Java?
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    1. USNeil Coffey
    1. USNeil Coffey
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    1. POWhat is the purpose of long, double, byte, char in Java?
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    1. CONote that char only represents a character if all characters you use are inside the Basic Multilingual Plane (BMP) of Unicode. Once you leave the BMP, character handling in Java is *very* funky. No necessarily something you need to care about if you only handle western languages, but you should be aware of it.
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    2. COSee e.g. this question & answer for an explanation: http://stackoverflow.com/questions/2533097/java-unicode-encoding
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    3. COThe only advantage I can think of to `byte` and `short` primitives is that the compiler allows them to be stored directly `byte[]` and `short[]` arrays but will not allow an `int` to be stored without a typecast. Is there any other advantage?
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