Java Class Library

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The Java Class Library (JCL) is a set of dynamically loadable libraries that Java Virtual Machine (JVM) languages can call at run time. Because the Java Platform is not dependent on a specific operating system, applications cannot rely on any of the platform-native libraries. Instead, the Java Platform provides a comprehensive set of standard class libraries, containing the functions common to modern operating systems.

JCL serves three purposes within the JVM:

• Like other standard code libraries, they provide the programmer a well-known set of useful facilities, such as container classes and regular expression processing.
• The library provides an abstract interface to tasks that would normally depend heavily on the hardware and operating system, such as network access and file access.
• Some underlying platforms may not support all of the features a Java application expects. In these cases, the library implementation can either emulate those features or provide a consistent way to check for the presence of a specific feature.