Java was released in the year of 1995 with the philosophy "write once, run anywhere." Java is most popular and preferred programming language and theoretically, Java programs can be executed on any machine that supports or features Java Java Runtime Environment (JRE). But in practice or real-time, the execution of Java codes needs certain caveats (predetermined conditions and limitations). Java is a powerful and versatile programming language which will run on several platforms. Nowadays, latest versions of the Java virtual machine operate on a bunch of various electronic systems, as well as computers and smartphones.
Java is a high level object oriented programming language, that represents logical computer concepts in a way that's easier for humans to comprehend than high-level machine language or programming language. Be that as it may, this implies that in order to run Java codes on a machine or computer, the code should be compiled into machine readable language or code and interpreted by a computer or other machines. To accomplish its goal of "Write once, run anywhere," Java features both - a Java compiler which converts Java code into machine readable code and then the Java Virtual Machine interprets the code to execute on the computer or on the device which it runs on.
Individual computers typically use completely different machine languages, therefore if you compile a Java program to one particular machine language, then the compiled program would not be able to run on other computers or devices. In order to overcome this drawback, the Java Virtual Machine (JVM) is a simulated machine that has multiple implementations for every other device that supports Java programming language. Once Java code is compiled into JVM bytecode, the bytecode then runs in line with the JVM. The JVM then passes the particular process work to the processor in its own language. The JVM is part of the Java Runtime Environment (JRE).
To understand the core of concepts of Java, it is recommended to take up Java course to become programmer.