The Java Runtime Environment includes a Just-In-Time compiler that improves the efficiency of Java-based programmes at runtime. JIT lowers compilation time by compiling bytecodes with comparable functionality in parallel.
At the start of a java application, a method might be called millions of times. As a result, rather than compiling each method, Java OpenJ9 keeps track of how many times a method is used. The JIT compiler is started when the initiation count exceeds a specified threshold.
JIT stands for Just In Time. JIT compiler is a program which converts the Java ByteCode into processor level instructions.
The JIT compiler runs after the program has begun and compiles the bytecode while the program is running into a quicker and more local processor level directive set.
After you’ve completed writing a Java program, the source code are compiled by the Java compiler into bytecode. Then the bytecode is converted into processor level instructions by the JIT compiler. Thus the JIT compiler acts as a second compiler.
The JIT compiler runs simultaneously with the execution of the program. It compiles the bytecode into platform-specific executable code that is instantly executed.