Java diagnostic commands

jmap
jmap is a command-line utility that is included as part of the Java™ Development Kit (JDK). This utility prints memory-related statistics for a running JVM or core file.
jstat
The jstat utility uses the built-in instrumentation in the HotSpot JVM to provide information about performance and resource consumption of running applications.
HPROF: Heap Profiler
HPROF is a simple profiler agent that is shipped with JDK Version 5.0. It is a dynamically-linked library that interfaces to the JVM by using the Java Virtual Machine Tools Interface (JVM TI). It writes out profiling information either to a file or to a socket in ASCII or binary format. This information can be further processed by a profiler front-end tool.
HAT: Heap Analysis Tool
The Heap Analysis Tool (HAT) helps debug unintentional object retention. This term is used to describe an object that is no longer needed but is kept alive due to references through some path from a live object. HAT provides a convenient means to browse the object topology in a heap snapshot that is generated using HPROF. The tool allows a number of queries, including “show me all reference paths from the rootset to this object".
Diagnostic Tool for Java Garbage Collector
The Diagnostic Tool for Java Garbage Collector is a diagnostic tool for optimizing parameters affecting the garbage collector when using the IBM® Java virtual machine (JVM).
HeapAnalyzer
HeapAnalyzer finds a possible Java heap leak area through its heuristic search engine and analysis of the Java heap dump in Java applications.
HeapRoots
HeapRoots is a tool for debugging memory leaks in Java applications through analysis of "heap dumps."

Parent topic: Tools for troubleshooting