Memory Analyzer https://www.eclipse.org/mat/
Hang threads in Java Platform, Enterprise Edition applications (https://www.ibm.com/support/knowledgecenter/en/SSEQTP_9.0.5/com.ibm.websphere.base.doc/ae/ctrb_hangdetection.html)
WSVR0605W: Thread threadname has been active for hangtime and may be hung. There are totalthreads threads in total in the server that may be hung.
Where threadname is the name that appears in the JVM thread dump, hangtime is the approximate elapsed time since the thread was activated, and totalthreads is the overall rating of the system thread.
IBM Heap Analyzer https://www.ibm.com/support/pages/ibm-heapanalyzer
IBM Thread and Monitor Dump Analyzer for Java (TMDA) https://www.ibm.com/support/pages/ibm-thread-and-monitor-dump-analyzer-java-tmda
IBM Pattern Modeling and Analysis Tool for Java Garbage Collector (PMAT) https://www.ibm.com/support/pages/ibm-pattern-modeling-and-analysis-tool-java-garbage-collector-pmat
Check when GC is occurring + standard output, etc.