jstack

jstack is a command line tool used for collecting thread information from Java applications. It is included in the JDK (Java Development Kit) and is used for diagnosing and troubleshooting issues related to thread performance, deadlocks, and hangs in Java applications.

The tool allows you to capture a snapshot of all the threads running in a Java application at a specific point in time. It provides information about the state of each thread, such as the thread ID, name, priority, stack trace, and more.

jstack can be particularly useful when an application is unresponsive or consuming excessive CPU. By collecting thread information, it helps to identify which threads are active, what they are doing, and whether there are any bottlenecks or issues causing performance problems.

The tool can also identify deadlocks, which occur when two or more threads are waiting for each other's resources, causing a deadlock situation where none of the threads can proceed.

jstack provides various options to customize its behavior, allowing you to choose the format of the generated stack trace, specify the output file, and even attach to a running Java process.

The output generated by jstack can be analyzed manually to gain insights into the state of the threads and identify potential issues. It is often used in combination with other tools and debugging techniques to troubleshoot complex problems in Java applications.

Overall, jstack is an invaluable tool for Java developers and system administrators to diagnose and resolve performance issues related to threads in Java applications. Its ability to provide detailed information about thread behavior makes it an essential tool in Java application troubleshooting.