Java virtual machine (JVM)
Java Virtual Machine (JVM) is a software that is required for the execution of Java programs and is part of the Java Runtime Environment( JRE). Unlike Java programs themselves, the JVM is not platform-independent, but is a native program for the target platform. Java programs can be executed on any system for which a JVM conforming to the specifications is available.
After the source code has been converted into bytecode, it can be passed to the JVM. This looks for the entry point of the program (in the case of Java the main() method) and begins there with the execution. For this the program block to be executed is first compiled for the target system and then called. The compilation is done as Just In-time Compilation( JIT compilation).
The most serious disadvantage of this procedure is generally the increased resource requirement, which cannot be avoided due to the JVM to be executed and constant compilation processes. Optimizations in this area and the constant performance growth of the hardware let it step however in most application areas ever further into the background.
The second main task of the JVM, simplifies programming considerably compared to older languages such as C++ in particular: the management of the memory areas used. Java programmers are completely freed from the task of explicitly reserving and releasing memory areas. In addition to shorter development times, this results in more stable software that is less susceptible to memory leaks and security vulnerabilities such as buffer overflows. The most important function in this context is garbage collection. Automatic memory management works more reliably and securely, but not as efficiently as one implemented manually (and without errors). Therefore, there are definitely use cases in which Java is less suitable as a programming language than, for example, C++.