IndexOutOfBoundsException in ALERT Track constructor

[mathieuouillon]

The ALERT reconstruction engine crashes with an IndexOutOfBoundsException when processing certain events. The error occurs in Track.<init> at line 61 of Track.java, called from ALERTEngine.processDataEvent at line 349 of ALERTEngine.java. It appears the code attempts to access index 0 of an empty list without checking if the list is populated.

Stack Trace

2026-04-05 12:35:59.690: Error in 129.57.138.234%7440_java:clas12-3:ALERT (ID: 56909):
Error processing input event

    java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
        at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)
        at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
        at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
        at java.base/java.util.Objects.checkIndex(Objects.java:385)
        at java.base/java.util.ArrayList.get(ArrayList.java:427)
        at org.jlab.rec.ahdc.Track.Track.<init>(Track.java:61)
        at org.jlab.service.alert.ALERTEngine.processDataEvent(ALERTEngine.java:349)
        at org.jlab.clas.reco.ReconstructionEngine.filterEvent(ReconstructionEngine.java:368)
        at org.jlab.clas.reco.ReconstructionEngine.execute(ReconstructionEngine.java:407)
        at org.jlab.clara.sys.ServiceEngine.executeEngine(ServiceEngine.java:227)
        at org.jlab.clara.sys.ServiceEngine.execute(ServiceEngine.java:153)
        at org.jlab.clara.sys.Service.lambda$execute$2(Service.java:178)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
        at java.base/java.lang.Thread.run(Thread.java:1583)

Environment

• CJ 13.8.2
• timestamp: 04/04/2026-07:00:00