方法

compare

/*** 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)&gt;0) &amp;&amp; (compare(y, z)&gt;0))</tt> implies* <tt>compare(x, z)&gt;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.*/int compare(T o1, T o2);

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jdk Comparator接口

方法

compare

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