Compares its two arguments for order. Returns a negative integer,
zero, or a positive integer as the first argument is less than, equal
to, or greater than the second.<p>
In the foregoing description, the notation
<tt>sgn(</tt><i>expression</i><tt>)</tt> designates the mathematical
<i>signum</i> function, which is defined to return one of <tt>-1</tt>,
<tt>0</tt>, or <tt>1</tt> according to whether the value of
<i>expression</i> is negative, zero or positive.<p>
The implementor must ensure that <tt>sgn(compare(x, y)) ==
-sgn(compare(y, x))</tt> for all <tt>x</tt> and <tt>y</tt>. (This
implies that <tt>compare(x, y)</tt> must throw an exception if and only
if <tt>compare(y, x)</tt> throws an exception.)<p>
The implementor must also ensure that the relation is transitive:
<tt>((compare(x, y)>0) && (compare(y, z)>0))</tt> implies
<tt>compare(x, z)>0</tt>.<p>
Finally, the implementor must ensure that <tt>compare(x, y)==0</tt>
implies that <tt>sgn(compare(x, z))==sgn(compare(y, z))</tt> for all
<tt>z</tt>.<p>
It is generally the case, but <i>not</i> strictly required that
<tt>(compare(x, y)==0) == (x.equals(y))</tt>. Generally speaking,
any comparator that violates this condition should clearly indicate
this fact. The recommended language is "Note: this comparator
imposes orderings that are inconsistent with equals."
@param o1 the first object to be compared.
@param o2 the second object to be compared.
@return a negative integer, zero, or a positive integer as the
first argument is less than, equal to, or greater than the
second.
@throws NullPointerException if an argument is null and this
comparator does not permit null arguments
@throws ClassCastException if the arguments' types prevent them from
being compared by this comparator.
Compares its two arguments for order. Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.<p>
In the foregoing description, the notation <tt>sgn(</tt><i>expression</i><tt>)</tt> designates the mathematical <i>signum</i> function, which is defined to return one of <tt>-1</tt>, <tt>0</tt>, or <tt>1</tt> according to whether the value of <i>expression</i> is negative, zero or positive.<p>
The implementor must ensure that <tt>sgn(compare(x, y)) == -sgn(compare(y, x))</tt> for all <tt>x</tt> and <tt>y</tt>. (This implies that <tt>compare(x, y)</tt> must throw an exception if and only if <tt>compare(y, x)</tt> throws an exception.)<p>
The implementor must also ensure that the relation is transitive: <tt>((compare(x, y)>0) && (compare(y, z)>0))</tt> implies <tt>compare(x, z)>0</tt>.<p>
Finally, the implementor must ensure that <tt>compare(x, y)==0</tt> implies that <tt>sgn(compare(x, z))==sgn(compare(y, z))</tt> for all <tt>z</tt>.<p>
It is generally the case, but <i>not</i> strictly required that <tt>(compare(x, y)==0) == (x.equals(y))</tt>. Generally speaking, any comparator that violates this condition should clearly indicate this fact. The recommended language is "Note: this comparator imposes orderings that are inconsistent with equals."
@param o1 the first object to be compared. @param o2 the second object to be compared. @return a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. @throws NullPointerException if an argument is null and this comparator does not permit null arguments @throws ClassCastException if the arguments' types prevent them from being compared by this comparator.