JREstä

JREstä refers to the Java Runtime Environment. It is a software layer that allows computer programs written in the Java programming language to be executed. The JRE includes the Java Virtual Machine (JVM), which is the core component responsible for interpreting and executing Java bytecode. It also contains various class libraries and support files that are necessary for Java applications to run.

Essentially, the JRE acts as an intermediary between the compiled Java code and the underlying operating system and hardware. This abstraction is a key reason for Java's "write once, run anywhere" philosophy. Developers can compile their Java code on one platform, and as long as a compatible JRE is installed on another platform, the application can run without modification.

The JRE is distinct from the Java Development Kit (JDK). The JDK includes the JRE along with development tools such as compilers, debuggers, and other utilities necessary for writing and building Java applications. Users who only need to run Java applications, rather than develop them, typically only require the JRE. Oracle, the current steward of Java, provides the JRE for various operating systems. Updates to the JRE often address security vulnerabilities and introduce performance improvements.