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Integer type ranges are defined by the JLS, §4.2.1, "Integral Types and Values", [JLS 2005] and are also described in rule " NUM00-J. Detect or prevent integer overflow."

The table below presents the rules for narrowing primitive conversions of integer types. In the table, for an integer type T, n represents the number of bits used to represent the resulting type T (precision).

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Note that conversions from float to double or double to float can also lose information about the overall magnitude of the converted value. See rule "NUM06-J. Use the strictfp modifier for floating-point calculation consistency across platforms" for additional information.

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double i = Double.MIN_VALUE;
double j = Double.MAX_VALUE;
if ((i < Float.MIN_VALUE) || (i > Float.MAX_VALUE) ||
    (j < Float.MIN_VALUE) || (j > Float.MAX_VALUE)) {
  throw new ArithmeticException ("Value is out of range");    
}

float b = (float) i;
float c = (float) j;
//other operations

Exceptions

NUM12-EX0: Java's narrowing conversions are both well-defined and portable; knowledgeable programmers can intentionally apply such conversions in contexts where their output is both expected and reasonable. Consequently, narrowing conversions are permitted when the code contains comments that document both the use of narrowing conversions and that the potential for truncation has been anticipated. A suitable comment might read: "// Deliberate narrowing cast of i; possible truncation OK"

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