Summary
-------

Add a companion set of absolute value methods for `int` and `long` which throw an exception on the most negative value, whose absolute value is not representable in the same format.

Problem
-------

It is surprising, but true that Math.abs(Integer.MIN_VALUE) equals Integer.MIN_VALUE, a negative value; the some relationship holds for Long.MIN_VALUE. Having absolute value methods which threw exceptions for these exceptional cases would help remove bugs for an easy to overlook case.

Solution
--------

Add `absExact` methods for `int` and `long` to `java.lang.Math` and `java.lang.StrictMath`.

Specification
-------------

Equivalent methods are added to `java.lang.Math` and `java.lang.StrictMath`:

         /**
    +     * Returns the mathematical absolute value of an {@code int} value
    +     * if it is exactly representable as an {@code int}, throwing
    +     * {@code ArithmeticException} if the result overflows the
    +     * positive {@code int} range.
    +     *
    +     * <p>Since the range of two's complement integers is asymmetric
    +     * with one additional negative value, the mathematical absolute
    +     * value of {@link Integer#MIN_VALUE} overflows the positive
    +     * {@code int} range, so an exception is thrown for that argument.
    +     *
    +     * @param  a  the argument whose absolute value is to be determined
    +     * @return the absolute value of the argument, unless overflow occurs
    +     * @throws ArithmeticException if the argument is {@link Integer#MIN_VALUE}
    +     * @see Math#abs(int)
    +     * @since 15
    +     * @see Math#absExact(long)
    +     */
    +    public static int absExact(int a)
    
         /**
    +     * Returns the mathematical absolute value of an {@code long} value
    +     * if it is exactly representable as an {@code long}, throwing
    +     * {@code ArithmeticException} if the result overflows the
    +     * positive {@code long} range.
    +     *
    +     * <p>Since the range of two's complement integers is asymmetric
    +     * with one additional negative value, the mathematical absolute
    +     * value of {@link Long#MIN_VALUE} overflows the positive
    +     * {@code long} range, so an exception is thrown for that argument.
    +     *
    +     * @param  a  the argument whose absolute value is to be determined
    +     * @return the absolute value of the argument, unless overflow occurs
    +     * @throws ArithmeticException if the argument is {@link Long#MIN_VALUE}
    +     * @see Math#abs(long)
    +     * @since 15
    +     */
    +    public static long absExact(long a)