How does JIT compiler impact performance or memory usage?

The Just-In-Time (JIT) compiler plays a significant role in the performance and memory usage of Java applications. By compiling bytecode into native machine code at runtime, the JIT compiler optimizes execution speed and system resource usage.

When Java code is first executed, it runs via the Java Virtual Machine (JVM), which interprets the bytecode. However, as the same sections of code are repeatedly executed, the JIT compiler kicks in, converting high-frequency bytecode into optimized machine code. This process enhances performance by reducing interpretation overhead and allowing for optimization techniques, such as inlining methods and removing dead code.

Although the JIT compilation process requires memory for storing the compiled code, it typically results in overall memory savings over time as execution overhead decreases, especially for long-running applications. Thus, while JIT compilers can initially use more memory, they ultimately lead to better resource usage and increased speed.