Optimizing Java performance involves a combination of code optimization, efficient use of data structures, proper resource management, and tuning the Java Virtual Machine (JVM). Here are some key strategies and best practices for optimizing Java performance:

1. Efficient Code and Algorithms
Choose the Right Data Structures: Use appropriate data structures from the Java Collections Framework based on your needs (e.g., ArrayList vs. LinkedList, HashMap vs. TreeMap).
Optimize Algorithms: Focus on the complexity of algorithms. Use more efficient algorithms for sorting, searching, and other operations when dealing with large datasets.
Avoid Premature Optimization: While it's important to write efficient code, avoid optimizing too early. Focus on writing clear, maintainable code first and optimize only when necessary.
2. Memory Management
Minimize Object Creation: Reuse objects where possible, especially in high-frequency or performance-critical sections of the code.
Garbage Collection Tuning: Understand and tune garbage collection (GC) based on your application's needs. Use JVM options to select appropriate GC algorithms and settings.
Avoid Memory Leaks: Ensure that objects are dereferenced properly when no longer needed. Use tools like VisualVM or YourKit to detect memory leaks.
3. JVM Tuning
Heap Size Adjustment: Set the initial and maximum heap size (-Xms and -Xmx) appropriately to avoid frequent GC pauses or OutOfMemoryError.
JVM Options: Use JVM options for performance tuning, such as enabling the server JVM (-server), setting GC options (-XX:+UseG1GC), or optimizing the Just-In-Time (JIT) compiler (-XX:TieredCompilation).
Class Loading and Compilation: Reduce class loading times by keeping the classpath small and avoiding unnecessary classes. Enable class data sharing (-Xshareclasses).
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