The combination of the Java Virtual Machine (Java interpreter), the core class library and supporting files, all of which are required to run a Java program. See Java and Java Virtual Machine ...

Java code that is 100% compliant with the Java specification. A pure Java program does not rely on specific hardware features and will run in any machine under the Java Virtual Machine.

That has changed somewhat. Among other innovations, Visual Studio Code now has good support for editing, running, and debugging Java code through a set of Java-specific extensions.