Java - JRE


Java Runtime Environment (JRE) is a run-time image, which is a complete implementation of the Java SE Platform and contains the runtime executable (mostly the JVM, ie java) in order to run java application.

It can be installed independently or as part of the JDK.


The root directory of a JRE image contains two directories and release files:

  • bin: contains executable binaries, and in particular the java command for launching the run-time system. (On the Windows operating system it also contains the run-time system's dynamically-linked native libraries.)
  • lib: contains a variety of:
    • files
      • .properties and .policy files, most of which may be, though rarely are, edited by developers, deployers, and end users;
      • data files in assorted binary formats, e.g., fonts, color profiles, and time-zone data
      • JAR files, including rt.jar, which contain the run-time system's Java class and resource files.
      • The run-time system's dynamically-linked native libraries on the Linux, macOS, and Solaris operating systems.
    • subdirectories:
      • endorsed directory, which does not exist by default, into which JAR files containing implementations of endorsed standards and standalone technologies may be placed
      • ext directory: JAR files containing extensions or optional packages may be placed
  • Release file: COPYRIGHT, LICENSE and README, and a release file that describes the image in terms of simple key/value property pairs, e.g.,
SOURCE=" .:6432b2dd408c corba:298df76047a5 deploy:37dee16794aa hotspot:4fc288749a23 hotspot/make/closed:cd84f8043a44 hotspot/src/closed:3620a6fb1afe install:2356feb10ea1 jaxp:6da26fc7da9a jaxws:b32d94155990 jdk:5ca18caa6a57 jdk/make/closed:dcbff65c1442 jdk/src/closed:0959720b6927 langtools:d035a731ab59 nashorn:5a2c3b3dd919"

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