[jboss-jira] [JBoss JIRA] (DROOLS-5284) MVELTest.testTypeCoercionLongDivByInt fails with IBM JDK 8

Thu Apr 30 03:43:00 EDT 2020

    [ https://issues.redhat.com/browse/DROOLS-5284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14067542#comment-14067542 ] 

Toshiya Kobayashi edited comment on DROOLS-5284 at 4/30/20 3:42 AM:
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First of all, the expression in the unit test is not good. Java cannot compile this because Math.round() can accept only double or float.

{code:java}
15 * Math.round( new BigDecimal("49.4") ) / 100
{code}

Then, MVEL kindly try to find a "BestCandidate" method for this.

https://github.com/mvel/mvel/blob/mvel2-2.4.7.Final/src/main/java/org/mvel2/util/ParseTools.java#L232

So MVEL picks up

{code:java}
public static int java.lang.Math.round(float)
{code}

or

{code:java}
public static long java.lang.Math.round(double)
{code}

(Assuming MVEL can coerce BigDecimal to float or double).

However, these 2 methods has no superiority in terms of scoring for "BestCandidate". Both get score "4".

https://github.com/mvel/mvel/blob/mvel2-2.4.7.Final/src/main/java/org/mvel2/util/ParseTools.java#L312

So the result depends on which method was picked first (The method lists are given by Class.getMethods()).

In case of OpenJDK, Math.round(double) is picked. -> Finally, the expression results in (Long / Long) which returns Double by MathProcessor.

In case of IBM JDK Math.round(float) is picked. -> Finally, the expression results in (Integer / Integer) which returns Integer by IntDiv.

I think I can tweak the selection logic as Double is preferred coercion for BigDecimal.

was (Author: tkobayashi):
First of all, the expression in the unit test is not good. Java cannot compile this because Math.round() can accept only double or float.

{code:java}
15 * Math.round( new BigDecimal("49.4") ) / 100
{code}

Then, MVEL kindly find a "BestCandidate" method for this.

https://github.com/mvel/mvel/blob/mvel2-2.4.7.Final/src/main/java/org/mvel2/util/ParseTools.java#L232

So MVEL picks up

{code:java}
public static int java.lang.Math.round(float)
{code}

or

{code:java}
public static long java.lang.Math.round(double)
{code}