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When the value to be represented is too small to encode normally, it is encoded in denormalized form, indicated by an exponent value of Float.MIN_EXPONENT - 1 or Double.MIN_EXPONENT - 1. Denormalized floating-point numbers have an assumed 0 in the ones' place and have one or more leading zeros in the represented portion of their mantissa. These leading zero bits no longer function as significant bits of precision; consequently, the total precision of denormalized floating-point numbers is less than that of normalized floating-point numbers. Note that even using normalized numbers where precision is required can pose a risk. See rule NUM04-J. Do not use floating-point numbers if precise computation is required for more information.

Using denormalized numbers can severely impair the precision of floating-point calculations; as a result, denormalized numbers must not be used.

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The following code tests whether a float value is denormalized in FP-strict mode or for platforms that lack extended range support. Testing for denormalized numbers in the presence of extended range support is platform-dependent; see rule NUM06-J. Use the strictfp modifier for floating-point calculation consistency across platforms for additional information.

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