Runtime Environment

The Java™ runtime environment provides runtime support for Java applications.

The runtime environment includes a Java Virtual Machine (VM), which interprets Java bytecode at run time. Although the runtime environment is included with the IBM SDK, it is also available as a separate package on Linux® and Windows operating systems. There are a number of tools included with the runtime environment that are installed into the install_dir/jre/bin directory, unless otherwise specified.

Contents of the runtime environment

Core Classes
These classes are the compiled class files for the platform and must remain compressed for the compiler and interpreter to access them. Do not modify these classes; instead, create subclasses and override where you need to.
Trusted root certificates
From certificate signing authorities. These certificates are used to validate the identity of signed material.
Runtime environment tools
ControlPanel (Java Control Panel)
AIX® and Linux operating systems only, except Linux on IBM Z®. Configures your Runtime Environment.
ikeycmd (iKeyman command-line utility)
Allows you to manage keys, certificates, and certificate requests from the command line. For more information see the accompanying Security documentation.
ikeyman (iKeyman GUI utility)
Allows you to manage keys, certificates, and certificate requests. For more information see the accompanying Security documentation, which includes the iKeyman User Guide. There is also a command-line version of this utility.
Note: The GUI version of this utility is not supported on the z/OS operating system.
jaaslogon (Windows only)
A Windows service that enables JAAS Active Login applications to change their effective user at run time using the JAAS Active Login API.
java (Java Interpreter)
Runs Java classes. The Java Interpreter runs programs that are written in the Java programming language.
javacpl (Java Control Panel)
Windows operating systems only. Configures your Runtime Environment.
javaw (Java Interpreter)
Runs Java classes in the same way as the java command does, but does not use a console window.
javaws (Java Web Start)
AIX, Linux (IA® 32-bit, PPC32, and PPC64), and Windows operating systems only. Enables the deployment and automatic maintenance of Java applications. For more information, see Running Web Start (AIX, Linux, and Windows only).
jcontrol (Java Control Panel)
AIX and Linux operating systems only, except Linux on IBM Z. Configures your Runtime Environment.
jextract
Linux and AIX operating systems only. Packages system dumps with executable files and libraries, to create an archive file. This file can be used by the dump viewer tool (jdmpview) to get more information than from a system dump alone. For more information, see Dump extractor (jextract).
keytool (Key and Certificate Management Tool)
Manages a keystore (database) of private keys and their associated X.509 certificate chains that authenticate the corresponding public keys.
kinit
Obtains and caches Kerberos ticket-granting tickets.
klist
Displays entries in the local credentials cache and key table.
ktab
Manages the principal names and service keys stored in a local key table.
pack200
Transforms a JAR file into a compressed pack200 file using the Java gzip compressor.
policytool (Policy File Creation and Management Tool)
Creates and modifies the external policy configuration files that define the Java security policy for your installation. From Version 8, the graphical user interface of this tool has a slightly different look and feel. See Accessibility issues with the policytool graphical user interface (GUI) utility.
rmid (RMI activation system daemon)
Starts the activation system daemon so that objects can be registered and activated in a Java Virtual Machine (JVM).
rmiregistry (Java remote object registry)
Creates and starts a remote object registry on the specified port of the current host.
tnameserv (Common Object Request Broker Architecture (CORBA) transient naming service)
Starts the CORBA transient naming service.
unpack200
Transforms a packed file produced by pack200 into a JAR file.