Class ExactConversionsSupport

java.lang.Object
java.lang.runtime.ExactConversionsSupport
public final class ExactConversionsSupport extends Object
A testing conversion of a value is exact if it yields a result without loss of information or throwing an exception. Otherwise, it is inexact. Some conversions are always exact regardless of the value. These conversions are said to be unconditionally exact.

For example, a conversion from int to byte for the value 10 is exact because the result, 10, is the same as the original value. In contrast, if the int variable i stores the value 1000 then a narrowing primitive conversion to byte will yield the result -24. Loss of information has occurred: both the magnitude and the sign of the result are different than those of the original value. As such, a conversion from int to byte for the value 1000 is inexact. Finally a widening primitive conversion from byte to int is unconditionally exact because it will always succeed with no loss of information about the magnitude of the numeric value.

The methods in this class provide the run-time support for the exactness checks of testing conversions from a primitive type to primitive type. These methods may be used, for example, by Java compiler implementations to implement checks for instanceof and pattern matching runtime implementations. Unconditionally exact testing conversions do not require a corresponding action at run time and, for this reason, methods corresponding to these exactness checks are omitted here.

The run time conversion checks examine whether loss of information would occur if a testing conversion would be to be applied. In those cases where a floating-point primitive type is involved, and the value of the testing conversion is either signed zero, signed infinity or NaN, these methods comply with the following:

  • Converting a floating-point negative zero to an integer type is considered inexact.
  • Converting a floating-point NaN or infinity to an integer type is considered inexact.
  • Converting a floating-point NaN or infinity or signed zero to another floating-point type is considered exact.
Implementation Note:
Some exactness checks describe a test which can be redirected safely through one of the existing methods. Those are omitted too (i.e., byte to char can be redirected to isIntToCharExact(int), short to byte can be redirected to isIntToByteExact(int) and similarly for short to char, char to byte and char to short to the corresponding methods that take an int).
See Java Language Specification:
5.7.1 Exact Testing Conversions
5.7.2 Unconditionally Exact Testing Conversions
15.20.2 The instanceof Operator
Since:
23

  • Method Details

    • isIntToByteExact

      public static boolean isIntToByteExact(int n)
      Exactness method from int to byte
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isIntToShortExact

      public static boolean isIntToShortExact(int n)
      Exactness method from int to short
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isIntToCharExact

      public static boolean isIntToCharExact(int n)
      Exactness method from int to char
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isIntToFloatExact

      public static boolean isIntToFloatExact(int n)
      Exactness method from int to float
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isLongToByteExact

      public static boolean isLongToByteExact(long n)
      Exactness method from long to byte
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isLongToShortExact

      public static boolean isLongToShortExact(long n)
      Exactness method from long to short
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isLongToCharExact

      public static boolean isLongToCharExact(long n)
      Exactness method from long to char
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isLongToIntExact

      public static boolean isLongToIntExact(long n)
      Exactness method from long to int
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isLongToFloatExact

      public static boolean isLongToFloatExact(long n)
      Exactness method from long to float
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isLongToDoubleExact

      public static boolean isLongToDoubleExact(long n)
      Exactness method from long to double
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isFloatToByteExact

      public static boolean isFloatToByteExact(float n)
      Exactness method from float to byte
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isFloatToShortExact

      public static boolean isFloatToShortExact(float n)
      Exactness method from float to short
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isFloatToCharExact

      public static boolean isFloatToCharExact(float n)
      Exactness method from float to char
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isFloatToIntExact

      public static boolean isFloatToIntExact(float n)
      Exactness method from float to int
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isFloatToLongExact

      public static boolean isFloatToLongExact(float n)
      Exactness method from float to long
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isDoubleToByteExact

      public static boolean isDoubleToByteExact(double n)
      Exactness method from double to byte
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isDoubleToShortExact

      public static boolean isDoubleToShortExact(double n)
      Exactness method from double to short
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isDoubleToCharExact

      public static boolean isDoubleToCharExact(double n)
      Exactness method from double to char
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isDoubleToIntExact

      public static boolean isDoubleToIntExact(double n)
      Exactness method from double to int
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isDoubleToLongExact

      public static boolean isDoubleToLongExact(double n)
      Exactness method from double to long
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type

    • isDoubleToFloatExact

      public static boolean isDoubleToFloatExact(double n)
      Exactness method from double to float
      Implementation Requirements:
      relies on the notion of representation equivalence defined in the specification of the Double class.
      Parameters:
      n - value
      Returns:
      true if and only if the passed value can be converted exactly to the target type