JRE consists of the following components:

• Deployment technologies, including deployment, Java Web Start and Java Plug-in.
• User interface toolkits, including Abstract Window Toolkit (AWT), Swing, Java 2D, Accessibility, Image I/O, Print Service, Sound, drag and drop (DnD) and input methods.
• Integration libraries, including Interface Definition Language (IDL), Java Database Connectivity (JDBC), Java Naming and Directory Interface (JNDI), Remote Method Invocation (RMI), Remote Method Invocation Over Internet Inter-Orb Protocol (RMI-IIOP) and scripting.
• Other base libraries, including international support, input/output (I/O), extension mechanism, Beans, Java Management Extensions (JMX), Java Native Interface (JNI), Math, Networking, Override Mechanism, Security, Serialization and Java for XML Processing (XML JAXP).
• Lang and util base libraries, including lang and util, management, versioning, zip, instrument, reflection, Collections, Concurrency Utilities, Java Archive (JAR), Logging, Preferences API, Ref Objects and Regular Expressions.
• Java Virtual Machine (JVM), including Java HotSpot Client and Server Virtual Machines.

JRE 1.0 has evolved with a variety of class and package additions to the core libraries, and it has grown from a few hundred classes to several thousand in Java 2 Platform, Standard Edition (J2SE). Entirely new APIs have been introduced, and many of the original version 1.0 APIs have been deprecated. There has been a significant degree of criticism because of these massive additions.