BigDecimal类的用法-创新互联
算术运算
BigDecimalpowabsnegatepow
BigDecimalpublic
1， public BigDecimal add(BigDecimal augend)
BigDecimal:
result.intValue/intCompact = this.intValue/intCompact + augend. intValue/intCompact result.scale = max(this.scale, augend.scale) result.precision = 0
2， public BigDecimal add(BigDecimal augend, MathContext mc)
MathContextRounding
BigDecimalpublicnegate
public BigDecimal subtract(BigDecimal subtrahend, MathContext mc) {
if (mc.precision == 0)
return subtract(subtrahend);
// share the special rounding code in add()
return add(subtrahend.negate(), mc);
}result.intValue/intCompact = this.intValue/intCompact * multiplicand. intValue/intCompact result.scale = sum(this.scale, multiplicand.scale) result.precision = 0
mutiplymultiplyAndRound
result.intValue/intCompact = this.intValue/intCompact divisor. intValue/intCompact
result.scale = this.scale - divisor.scale
BigDecimal5public
1， public BigDecimal divide(BigDecimal divisor)
MathContext mc = new MathContext( (int)Math.min(this.precision() +
(long)Math.ceil(10.0*divisor.precision()/3.0),
Integer.MAX_VALUE),
RoundingMode.UNNECESSARY);
BigDecimal quotient;
try {
quotient = this.divide(divisor, mc);
} catch (ArithmeticException e) {
throw new ArithmeticException("Non-terminating decimal expansion; " +
"no exact representable decimal result.");
}MathContextMathContextprecision
Math.min(this.precision() + (long)Math.ceil(10.0*divisor.precision()/3.0),Integer.MAX_VALUE)
RoundingModeUNNECESSARY
precisionprecisionRoundingModeRounding
2， public BigDecimal divide(BigDecimal divisor, MathContext mc)
longBigIntegerdivideAndRound
private static BigDecimal divideAndRound(long ldividend, long ldivisor, int scale, int roundingMode, int preferredScale)
longquotientremainder
long q = ldividend / ldivisor; long r = ldividend % ldivisor;
qsign = ((ldividend < 0) == (ldivisor < 0)) ? 1 : -1;
remainder0rounding
if (r != 0) {
boolean increment = needIncrement(ldivisor, roundingMode, qsign, q, r);
return valueOf((increment ? q + qsign : q), scale);
}remainder0scale
private static BigDecimal divideAndRound(BigInteger bdividend, BigInteger bdivisor, int scale, int roundingMode, int preferredScale)
BigIntegerlongBigIntegerlong
quotientremainderlongBigIntegerMutableBigIntegerdivide
MutableBigInteger mdividend = new MutableBigInteger(bdividend.mag); MutableBigInteger mq = new MutableBigInteger(); MutableBigInteger mdivisor = new MutableBigInteger(bdivisor.mag); MutableBigInteger mr = mdividend.divide(mdivisor, mq);
0
qsign = (bdividend.signum != bdivisor.signum) ? -1 : 1;
longBigInteger
public
1， public BigDecimal pow(int n)
unscaled valuescaleBigDecimal
unscaled valueBigIntegerpowscalethis.scale *n
if (n < 0 || n > 999999999)
throw new ArithmeticException("Invalid operation");
// No need to calculate pow(n) if result will over/underflow.
// Don't attempt to support "supernormal" numbers.
int newScale = checkScale((long)scale * n);
return new BigDecimal(this.inflated().pow(n), newScale);n
2， public BigDecimal pow(int n, MathContext mc)
BigDecimalroundingX3.274-1996
int mag = Math.abs(n);
// ready to carry out power calculation...
BigDecimal acc = ONE; // accumulator
boolean seenbit = false; // set once we've seen a 1-bit
for (int i=1;;i++) { // for each bit [top bit ignored]
mag += mag; // shift left 1 bit
if (mag < 0) { // top bit is set
seenbit = true; // OK, we're off
acc = acc.multiply(lhs, workmc); // acc=acc*x
}
if (i == 31)
break; // that was the last bit
if (seenbit)
acc=acc.multiply(acc, workmc); // acc=acc*acc [square]
// else (!seenbit) no point in squaring ONE
}
// if negative n, calculate the reciprocal using working precision
if (n < 0) // [hence mc.precision>0]
acc=ONE.divide(acc, workmc);mag += magn
if(mag <0) 1BigDecimalseenbit
1 = 2^0*1i=31
n<01
125
1， 5101000…i=29
2， mag <0 => seenbit = true, acc = 1*12 = 12(12^1)
3， seenbit = true => acc = 12 * 12 = 144(12^2)
4， i= 30, mag 01000…
5， mag>0 => seenbittrue
6， seenbit =true => acc = acc * acc = 144* 144(12^4)
7， i=31mag1000…
8， mag<0=>seenbit = true,acc = acc * 12 = 144*144*12(12^5)
9， i = 31 =>
doRound
setScale
setScaleBigDecimalBigDecimalintVal, intCompact,precision,scalescaleunscaled value
BigDecimal
public BigDecimal setScale(int newScale, int roundingMode)
unscaled value
1， intCompactunscaled value
scaleLong.MAX_VALUEdivideAndRound
2， intValunscaled value
intCompactBigIntegerlong
compareTo
compareToBigDecimal
if (scale == val.scale) {
long xs = intCompact;
long ys = val.intCompact;
if (xs != INFLATED && ys != INFLATED)
return xs != ys ? ((xs > ys) ? 1 : -1) : 0;
}BigDecimalunscaled valuescalescaleunscaled valueintCompactlong
int xsign = this.signum(); int ysign = val.signum(); if (xsign != ysign) return (xsign > ysign) ? 1 : -1;
if (xsign == 0) return 0;
00
int cmp = compareMagnitude(val);
compareMagnitude
long xae = (long)this.precision() - this.scale; // [-1] long yae = (long)val.precision() - val.scale; // [-1] if (xae < yae) return -1; if (xae > yae) return 1;
precision – scale
sdiffscalescaleBigIntegercompareMagnitude
for (int i = 0; i < len1; i++) {
int a = m1[i];
int b = m2[i];
if (a != b)
return ((a & LONG_MASK) < (b & LONG_MASK)) ? -1 : 1;
}intLONG_MASK0.
return (xsign > 0) ? cmp : -cmp;
equals
equalsArrayListcontainsBigDecimalequals
if (scale != xDec.scale) return false;
BigDecimalscaleBigDecimalBigDecimal(“0”)BigDecimal(“0.0”)
BigDecimal a = new BigDecimal("0.0");
BigDecimal b = BigDecimal.ZERO;
System.out.print(a.equals(b));//falsecompareToequals
BigDecimalBigDecimal
BigDecimalunscaled valuescaleBigDecimalBigIntegerint
– doubleDoubletoString
BigIntegerLongunscaled valuescalescaleMathContextroundingMathContextX3.274-1996
doRoundsetScalecompareToequalsdoRoundsetScalecompareToequalsequalscompareTo0
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本文标题：BigDecimal类的用法-创新互联
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