Summary

Add a square root method to BigDecimal.

Problem

BigDecimal does not have a sqrt method.

Solution

Add a sqrt method to BigDecimal.

Specification

/**
+     * Returns an approximation to the square root of {@code this}
+     * with rounding according to the context settings.
+     *
+     * <p>The preferred scale of the returned result is equal to
+     * {@code floor(this.scale()/2.0)}. The value of the returned
+     * result is always within one ulp of the exact decimal value for
+     * the precision in question.  If the rounding mode is {@link
+     * RoundingMode#HALF_UP HALF_UP}, {@link RoundingMode#HALF_DOWN
+     * HALF_DOWN}, or {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
+     * result is within one half an ulp of the exact decimal value.
+     *
+     * <p>Special case:
+     * <ul>
+     * <li> The square root of {@code ZERO} is {@code ZERO}
+     * </ul>
+     *
+     * @param mc the context to use.
+     * @return the square root of {@code this}.
+     * @throws ArithmeticException if {@code this} is less than zero.
+     * @throws ArithmeticException if an exact result is requested
+     * ({@code mc.getPrecision()==0}) and there is no finite decimal
+     * expansion of the exact result
+     * @throws ArithmeticException if
+     * {@code (mc.getRoundingMode()==RoundingMode.UNNECESSARY}) and
+     * the exact result cannot fit in {@code mc.getPrecision()}
+     * digits.
+     * @since  9
+     */
+    BigDecimal sqrt(MathContext mc) {