JIT compiler, also known as "Just-In-Time" compiler, is an important component of the Java runtime environment, designed to enhance the execution efficiency of Java programs. It operates internally within the Java Virtual Machine (JVM) and converts Java bytecode into native machine code specific to the system. This process occurs at runtime rather than during compilation. The JIT compiler analyzes Java bytecode to identify "hot spots"—code blocks with high execution frequency—and compiles them into native machine code, thereby accelerating program execution. By leveraging runtime-specific information, it dynamically optimizes performance, improving efficiency as the program executes.