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java.math
public enum class: RoundingMode [javadoc | source]
java.lang.Enum
   java.math.RoundingMode
Specifies a rounding behavior for numerical operations capable of discarding precision. Each rounding mode indicates how the least significant returned digit of a rounded result is to be calculated. If fewer digits are returned than the digits needed to represent the exact numerical result, the discarded digits will be referred to as the discarded fraction regardless the digits' contribution to the value of the number. In other words, considered as a numerical value, the discarded fraction could have an absolute value greater than one.

Each rounding mode description includes a table listing how different two-digit decimal values would round to a one digit decimal value under the rounding mode in question. The result column in the tables could be gotten by creating a {@code BigDecimal} number with the specified value, forming a MathContext object with the proper settings ({@code precision} set to {@code 1}, and the {@code roundingMode} set to the rounding mode in question), and calling round on this number with the proper {@code MathContext}. A summary table showing the results of these rounding operations for all rounding modes appears below.

Summary of Rounding Operations Under Different Rounding Modes
Result of rounding input to one digit with the given rounding mode
Input Number {@code UP} {@code DOWN} {@code CEILING} {@code FLOOR} {@code HALF_UP} {@code HALF_DOWN} {@code HALF_EVEN} {@code UNNECESSARY}
5.5 6 5 6 5 6 5 6 throw {@code ArithmeticException}
2.5 3 2 3 2 3 2 2 throw {@code ArithmeticException}
1.6 2 1 2 1 2 2 2 throw {@code ArithmeticException}
1.1 2 1 2 1 1 1 1 throw {@code ArithmeticException}
1.0 1 1 1 1 1 1 1 1
-1.0 -1 -1 -1 -1 -1 -1 -1 -1
-1.1 -2 -1 -1 -2 -1 -1 -1 throw {@code ArithmeticException}
-1.6 -2 -1 -1 -2 -2 -2 -2 throw {@code ArithmeticException}
-2.5 -3 -2 -2 -3 -3 -2 -2 throw {@code ArithmeticException}
-5.5 -6 -5 -5 -6 -6 -5 -6 throw {@code ArithmeticException}

This {@code enum} is intended to replace the integer-based enumeration of rounding mode constants in BigDecimal (BigDecimal#ROUND_UP , BigDecimal#ROUND_DOWN , etc. ).

Field Summary
public  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:
Input Number Input rounded to one digit
with {@code 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
 

public  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:
Input Number Input rounded to one digit
with {@code 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
 

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

Example:
Input Number Input rounded to one digit
with {@code 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
 

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

Example:
Input Number Input rounded to one digit
with {@code 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
 

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

Example:
Input Number Input rounded to one digit
with {@code 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
 

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

Example:
Input Number Input rounded to one digit
with {@code 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
 

public  RoundingMode HALF_EVEN    Rounding mode to round towards the {@literal "nearest neighbor"} unless both neighbors are equidistant, in which case, round towards the even neighbor. Behaves as for {@code RoundingMode.HALF_UP} if the digit to the left of the discarded fraction is odd; behaves as for {@code 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 {@literal "Banker's rounding,"} and is chiefly used in the USA. This rounding mode is analogous to the rounding policy used for {@code float} and {@code double} arithmetic in Java.

Example:
Input Number Input rounded to one digit
with {@code 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
 

public  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 {@code ArithmeticException} is thrown.

Example:
Input Number Input rounded to one digit
with {@code UNNECESSARY} rounding
5.5 throw {@code ArithmeticException}
2.5 throw {@code ArithmeticException}
1.6 throw {@code ArithmeticException}
1.1 throw {@code ArithmeticException}
1.0 1
-1.0 -1
-1.1 throw {@code ArithmeticException}
-1.6 throw {@code ArithmeticException}
-2.5 throw {@code ArithmeticException}
-5.5 throw {@code ArithmeticException}
 

public final  int oldMode     
Method from java.math.RoundingMode Summary:
valueOf
Method from java.math.RoundingMode Detail:
 public static RoundingMode valueOf(int rm) 
    Returns the {@code RoundingMode} object corresponding to a legacy integer rounding mode constant in BigDecimal .