Java performance monitoring is essential for ensuring that Java applications run smoothly, efficiently, and meet performance requirements. Poorly performing Java applications can have a significant negative impact on various areas of business, from customer satisfaction to employee productivity. There are several types of Java monitoring tools available, including basic JVM monitoring tools, profiling tools, application performance monitoring (APM) solutions, metrics and analytics platforms, logging and log analysis tools, memory analysis tools, thread analysis tools, and real-time monitoring and alerting tools. To improve Java application performance, developers can optimize their Java code by avoiding recursion, leveraging StringBuilder, using stack allocations instead of heap allocations, choosing the right garbage collector, and identifying and fixing slow critical regions. Additionally, a good monitoring tool provides actionable real-time insight into how an application is performing, including observability into JVMs running the application, detailed insights into slow transactions, and proactive alerting if issues arise.