It appears we are assuming that Integers and Longs can be compared to one another just because they Implement Comparable is a bad assumption, This probably isn't what was expected. These objects implement Comparable, but they throw exceptions when specific requirements are not met. I can't say that its a very elegant solution on Sun's part.
Ouch <snip from Integer>:
/**
* Compares this <code>Integer</code> object to another object.
* If the object is an <code>Integer</code>, this function behaves
* like <code>compareTo(Integer)</code>. Otherwise, it throws a
* <code>ClassCastException</code> (as <code>Integer</code>
* objects are only comparable to other <code>Integer</code>
* objects).
*
* @param o the <code>Object</code> to be compared.
* @return the value <code>0</code> if the argument is a
* <code>Integer</code> numerically equal to this
* <code>Integer</code>; a value less than <code>0</code>
* if the argument is a <code>Integer</code> numerically
* greater than this <code>Integer</code>; and a value
* greater than <code>0</code> if the argument is a
* <code>Integer</code> numerically less than this
* <code>Integer</code>.
* @exception <code>ClassCastException</code> if the argument is not an
* <code>Integer</code>.
* @see java.lang.Comparable
* @since 1.2
*/
public int compareTo(Object o) {
return compareTo((Integer)o);
}
Mark R. Diggory wrote:
I looked over the code and the default comparator uses the default "compare" method of the object. All ints and longs are wrapped in a "Long" before being added to the Frequency table. I suspect that the Long objects being added cannot be compared to the Character objects without throwing an error?
The other thought is that the NaturalComparator is not added to default TreeMap when its created.
Frequency.NaturalComparator
http://jakarta.apache.org/commons/math/xref/org/apache/commons/math/stat/Frequency.html#401
public int compare(Object o1, Object o2) { return ((Comparable)o1).compareTo(o2); }
Shing Hing Man wrote:
Deal all, It would be appreciated if someone could clarify the following on org.apache.commons.math.stat.univariate.Frequency.
My version of org.apache.commons.math is dated 10
August, 2004.
The following snippet piece of code is from
http://jakarta.apache.org/commons/math/userguide/stat.html#1.3%20Frequency%20distributions
Frequency f = new Frequency(); f.addValue(1); f.addValue(new Integer(1)); // (*) f.addValue(new Long(1)); f.addValue(2); f.addValue(new Integer(-1)); System.out.println(f.getCount(1)); // displays 3 System.out.println(f.getCumPct(0)); // displays 0.2 System.out.println(f.getPct(new Integer(1))); // displays 0.6 System.out.println(f.getCumPct(-2)); // displays 0 System.out.println(f.getCumPct(10)); // displays 1
When I run it, I got the following exception at line (*).
Exception in thread "main" java.lang.IllegalArgumentException: Value not comparable to existing values.
It looks as though the default comparator can not compare primitive type int with Integer object. I thought this piece of code is supposed to demonstrate the otherwise.
Thanks in advice for your help !
Shing
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