Java compact1, compact2, compact3 java.math Enum RoundingMode（JDK8）

Enum Constant Detail

• UP

  public static final RoundingMode UP

  Rounding mode to round away from zero. Always increments the digit prior to a non-zero discarded fraction. Note that this rounding mode never decreases the magnitude of the calculated value.

  Example:

  Rounding mode UP Examples

  Input Number	Input rounded to one digit with UP rounding
  5.5	6
  2.5	3
  1.6	2
  1.1	2
  1.0	1
  -1.0	-1
  -1.1	-2
  -1.6	-2
  -2.5	-3
  -5.5	-6

• DOWN

  public static final RoundingMode DOWN

  Rounding mode to round towards zero. Never increments the digit prior to a discarded fraction (i.e., truncates). Note that this rounding mode never increases the magnitude of the calculated value.

  Example:

  Rounding mode DOWN Examples

  Input Number	Input rounded to one digit with DOWN rounding
  5.5	5
  2.5	2
  1.6	1
  1.1	1
  1.0	1
  -1.0	-1
  -1.1	-1
  -1.6	-1
  -2.5	-2
  -5.5	-5

• CEILING

  public static final RoundingMode CEILING

  Rounding mode to round towards positive infinity. If the result is positive, behaves as for RoundingMode.UP; if negative, behaves as for RoundingMode.DOWN. Note that this rounding mode never decreases the calculated value.

  Example:

  Rounding mode CEILING Examples

  Input Number	Input rounded to one digit with CEILING rounding
  5.5	6
  2.5	3
  1.6	2
  1.1	2
  1.0	1
  -1.0	-1
  -1.1	-1
  -1.6	-1
  -2.5	-2
  -5.5	-5

• FLOOR

  public static final RoundingMode FLOOR

  Rounding mode to round towards negative infinity. If the result is positive, behave as for RoundingMode.DOWN; if negative, behave as for RoundingMode.UP. Note that this rounding mode never increases the calculated value.

  Example:

  Rounding mode FLOOR Examples

  Input Number	Input rounded to one digit with FLOOR rounding
  5.5	5
  2.5	2
  1.6	1
  1.1	1
  1.0	1
  -1.0	-1
  -1.1	-2
  -1.6	-2
  -2.5	-3
  -5.5	-6

• HALF_UP

  public static final RoundingMode HALF_UP

  Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. Behaves as for RoundingMode.UP if the discarded fraction is ≥ 0.5; otherwise, behaves as for RoundingMode.DOWN. Note that this is the rounding mode commonly taught at school.

  Example:

  Rounding mode HALF_UP Examples

  Input Number	Input rounded to one digit with HALF_UP rounding
  5.5	6
  2.5	3
  1.6	2
  1.1	1
  1.0	1
  -1.0	-1
  -1.1	-1
  -1.6	-2
  -2.5	-3
  -5.5	-6

• HALF_DOWN

  public static final RoundingMode HALF_DOWN

  Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. Behaves as for RoundingMode.UP if the discarded fraction is > 0.5; otherwise, behaves as for RoundingMode.DOWN.

  Example:

  Rounding mode HALF_DOWN Examples

  Input Number	Input rounded to one digit with HALF_DOWN rounding
  5.5	5
  2.5	2
  1.6	2
  1.1	1
  1.0	1
  -1.0	-1
  -1.1	-1
  -1.6	-2
  -2.5	-2
  -5.5	-5

• HALF_EVEN

  public static final RoundingMode HALF_EVEN

  Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as for RoundingMode.HALF_UP if the digit to the left of the discarded fraction is odd; behaves as for RoundingMode.HALF_DOWN if it's even. Note that this is the rounding mode that statistically minimizes cumulative error when applied repeatedly over a sequence of calculations. It is sometimes known as "Banker's rounding," and is chiefly used in the USA. This rounding mode is analogous to the rounding policy used for float and double arithmetic in Java.

  Example:

  Rounding mode HALF_EVEN Examples

  Input Number	Input rounded to one digit with HALF_EVEN rounding
  5.5	6
  2.5	2
  1.6	2
  1.1	1
  1.0	1
  -1.0	-1
  -1.1	-1
  -1.6	-2
  -2.5	-2
  -5.5	-6

• UNNECESSARY

  public static final RoundingMode UNNECESSARY

  Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary. If this rounding mode is specified on an operation that yields an inexact result, an ArithmeticException is thrown.

  Example:

  Rounding mode UNNECESSARY Examples

  Input Number	Input rounded to one digit with UNNECESSARY rounding
  5.5	throw ArithmeticException
  2.5	throw ArithmeticException
  1.6	throw ArithmeticException
  1.1	throw ArithmeticException
  1.0	1
  -1.0	-1
  -1.1	throw ArithmeticException
  -1.6	throw ArithmeticException
  -2.5	throw ArithmeticException
  -5.5	throw ArithmeticException

Method Detail

• values

  public static RoundingMode[] values()

  Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

  for (RoundingMode c : RoundingMode.values())
      System.out.println(c);
  

  Returns:

  an array containing the constants of this enum type, in the order they are declared

• valueOf

  public static RoundingMode valueOf(String name)

  Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

  Parameters:

  name - the name of the enum constant to be returned.

  Returns:

  the enum constant with the specified name

  Throws:

  IllegalArgumentException - if this enum type has no constant with the specified name

  NullPointerException - if the argument is null

• valueOf

  public static RoundingMode valueOf(int rm)

  Returns the RoundingMode object corresponding to a legacy integer rounding mode constant in BigDecimal.

  Parameters:

  rm - legacy integer rounding mode to convert

  Returns:

  RoundingMode corresponding to the given integer.

  Throws:

  IllegalArgumentException - integer is out of range