[AMQ-4826] Avoid unnecessary remainder operator for floating-point

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 5.9.0
• Fix Version/s: 5.9.1, 5.10.0
• Component/s: Transport

Environment

OS: OpenSUSE 12.2
JDK: Linux ARM Softfloat(jdk-7u45-linux-arm-vfp-sflt.tar.gz)
Hardware: pandaboard

• Assignee: Claus Ibsen
• Reporter: Ryuken SEKI
• Created: 25/Oct/13 08:33
• Updated: 02/Apr/14 23:53
• Resolved: 03/Nov/13 09:59

Description

I installed jdk-7u45-linux-arm-vfp-sflt.tar.gz on my pandaboard, and found that this jdk has a problem of remainder operator for floating point. So, if you starts ActiveMQ in above environment, you might encounter IndexOutOfBoundsException at
org.apache.activemq.transport.failover.FailoverTransport.getConnectList(FailoverTransport.java:779)

This is because
int p = (int) (Math.random() * 100 % l.size());
above p gets larger number than "l.size" contrary to your expectation. This problem doesn't occur in case of x86 Architecture or ARM Hardfloat JDK.

This is a problem of ARM Softfloat JDK, but I think it's better to avoid unnecessary remainder operator for floating-point for safety. So,
int p = ((int) Math.random() * 100) % l.size();
would be better than current one.