Java : MathContext with Examples

final var three = new BigDecimal(3);
System.out.println(three); // 3
System.out.println(three.scale()); // 0

// １０÷３
System.out.println(BigDecimal.TEN.divide(three, RoundingMode.CEILING)); // 4

{
    final var mc = new MathContext(3, RoundingMode.CEILING);
    System.out.println(mc); // precision=3 roundingMode=CEILING
    System.out.println(BigDecimal.TEN.divide(three, mc)); // 3.34
}

{
    final var mc = new MathContext(3, RoundingMode.FLOOR);
    System.out.println(mc); // precision=3 roundingMode=FLOOR
    System.out.println(BigDecimal.TEN.divide(three, mc)); // 3.33
}

static final MathContext DECIMAL128

A MathContext object with a precision setting matching the precision of the IEEE 754-2019 decimal128 format, 34 digits, and a rounding mode of HALF_EVEN.

// precision=34 roundingMode=HALF_EVEN
System.out.println(MathContext.DECIMAL128);

static final MathContext DECIMAL32

A MathContext object with a precision setting matching the precision of the IEEE 754-2019 decimal32 format, 7 digits, and a rounding mode of HALF_EVEN.

// precision=7 roundingMode=HALF_EVEN
System.out.println(MathContext.DECIMAL32);

static final MathContext DECIMAL64

A MathContext object with a precision setting matching the precision of the IEEE 754-2019 decimal64 format, 16 digits, and a rounding mode of HALF_EVEN.

// precision=16 roundingMode=HALF_EVEN
System.out.println(MathContext.DECIMAL64);

static final MathContext UNLIMITED

A MathContext object whose settings have the values required for unlimited precision arithmetic.

// precision=0 roundingMode=HALF_UP
System.out.println(MathContext.UNLIMITED);

// １０÷３
final var three = new BigDecimal(3);
System.out.println(three); // 3

// ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.
//BigDecimal.TEN.divide(three, MathContext.UNLIMITED);

MathContext (int setPrecision)

Constructs a new MathContext with the specified precision and the HALF_UP rounding mode.

final var mc = new MathContext(16);
System.out.println(mc); // precision=16 roundingMode=HALF_UP

MathContext (int setPrecision, RoundingMode setRoundingMode)

Constructs a new MathContext with a specified precision and rounding mode.

final var mc = new MathContext(8, RoundingMode.CEILING);
System.out.println(mc); // precision=8 roundingMode=CEILING

MathContext (String val)

Constructs a new MathContext from a string.

final var mc = new MathContext("precision=32 roundingMode=FLOOR");
System.out.println(mc); // precision=32 roundingMode=FLOOR

boolean equals (Object x)

Compares this MathContext with the specified Object for equality.

final var mc1 = new MathContext(8, RoundingMode.CEILING);
final var mc2 = new MathContext(8, RoundingMode.CEILING);

System.out.println(mc1 != mc2); // true
System.out.println(mc1.equals(mc2)); // true

final var mc3 = new MathContext(8, RoundingMode.FLOOR);
final var mc4 = new MathContext(4, RoundingMode.FLOOR);

System.out.println(mc1.equals(mc3)); // false
System.out.println(mc1.equals(mc4)); // false
System.out.println(mc3.equals(mc4)); // false

int getPrecision ()

Returns the precision setting.

final var mc = new MathContext(32);
System.out.println(mc); // precision=32 roundingMode=HALF_UP
System.out.println(mc.getPrecision()); // 32

System.out.println(MathContext.DECIMAL64); // precision=16 roundingMode=HALF_EVEN
System.out.println(MathContext.DECIMAL64.getPrecision()); // 16

RoundingMode getRoundingMode ()

Returns the roundingMode setting.

final var mc = new MathContext(8, RoundingMode.FLOOR);
System.out.println(mc); // precision=8 roundingMode=FLOOR
System.out.println(mc.getRoundingMode()); // FLOOR

System.out.println(MathContext.DECIMAL64); // precision=16 roundingMode=HALF_EVEN
System.out.println(MathContext.DECIMAL64.getRoundingMode()); // HALF_EVEN

int hashCode ()

Returns the hash code for this MathContext.

final var mc1 = new MathContext(8, RoundingMode.CEILING);
final var mc2 = new MathContext(8, RoundingMode.CEILING);

System.out.println(mc1 != mc2); // true
System.out.println(mc1.hashCode()); // -1237294828
System.out.println(mc2.hashCode()); // -1237294828

final var mc3 = new MathContext(8, RoundingMode.FLOOR);
final var mc4 = new MathContext(4, RoundingMode.FLOOR);

System.out.println(mc3.hashCode()); // -321581207
System.out.println(mc4.hashCode()); // -321581211

String toString ()

Returns the string representation of this MathContext.

final var mc = new MathContext(8, RoundingMode.FLOOR);

final var str1 = mc.toString();
System.out.println(str1); // precision=8 roundingMode=FLOOR

final var str2 = MathContext.DECIMAL64.toString();
System.out.println(str2); // precision=16 roundingMode=HALF_EVEN