In Java, bytecode refers to the compiled code that is generated by the Java compiler from the source code written by the developer. Bytecode is a highly optimized, platform-independent format that can be executed by any Java Virtual Machine (JVM), regardless of the underlying hardware and operating system.
Bytecode is essentially a set of instructions that the JVM can understand and execute. When a Java program is compiled, the source code is translated into bytecode which is then saved in a .class file. The bytecode is not machine code specific, which means it can run on any platform that has a JVM installed.
The advantage of using bytecode is that it makes Java highly portable and enables “write once, run anywhere” (WORA) capabilities. Since bytecode is not machine code specific, developers can create Java programs on one platform and run them on any platform that has a compatible JVM installed, without having to recompile the code.
When a Java program is executed, the JVM reads the bytecode and translates it into machine code that can be executed by the host operating system. This process is called just-in-time (JIT) compilation, and it allows the JVM to optimize the bytecode for the specific hardware and operating system on which the code is running, resulting in improved performance.