Contents - Cultural View

Java Class Library 156
[15] "Freetype font rasteriser" (http:/ / mail. openjdk. java. net/ pipermail/ font-scaler-dev/ 2007-August/ 000011. html). 2007-08-07. . Retrieved
2007-11-24.
[16] phoneme.dev.java.net/ (https:/ / phoneme. dev. java. net/ )
[17] graphics-rasterizer project page (http:/ / openjdk. java. net/ projects/ graphics-rasterizer/ )
[18] Graham, Jim (2007-10-03). "Open Source rasterizer" (http:/ / mail. openjdk. java. net/ pipermail/ 2d-dev/ 2007-October/ 000078. html). Sun
Microsystems. . Retrieved 2007-05-09.
[19] "Javascript is encumbered and there is no javascript plugin support." (http:/ / icedtea. classpath. org/ bugzilla/ show_bug. cgi?id=85).
IcedTea. 2008-03-11. . Retrieved 2008-06-01. "Changing Summary. JavaScript is no longer encumbered, but we still need liveconnect
support."
[20] http:/ / java. sun. com/ j2se/
[21] http:/ / java. sun. com/ reference/ api/ index. html
[22] https:/ / jdk7. dev. java. net/
[23] http:/ / java. sun. com/ javase/ 6/
[24] http:/ / java. sun. com/ j2se/ 1. 5. 0/
[25] http:/ / java. sun. com/ j2se/ 1. 4. 2/
[26] http:/ / java. sun. com/ j2se/ 1. 3/
Java Classloader
The Java Classloader is a part of the Java Runtime Environment that dynamically loads Java classes into the Java
Virtual Machine [1] . Usually classes are only loaded on demand. The Java run time system does not need to know
about files and file systems because of class loaders. Delegation is an important concept to understand when learning
about class loaders.
A software library is a collection of more or less related object code. In the Java language, libraries are typically
packaged in Jar files. Libraries can contain objects of different types. The most important type of object contained in
a Jar file is a Java class. A class can be thought of as a named unit of code. The class loader is responsible for
locating libraries, reading their contents, and loading the classes contained within the libraries. This loading is
typically done "on demand", in that it does not occur until the class is actually used by the program. A class with a
given name can only be loaded once by a given classloader.
Class loading process
Each Java class must be loaded by a class loader [2] . Furthermore, Java programs may make use of external libraries
(that is, libraries written and provided by someone other than the author of the program) or may itself be composed,
at least in part, by a number of libraries.
When the JVM is started, three class loaders are used [3] [4] :
1. Bootstrap class loader
2. Extensions class loader
3. System class loader
The bootstrap class loader loads the core Java libraries [5] (/lib directory). This class loader, which
is part of the core JVM, is written in native code.
The extensions class loader loads the code in the extensions directories (/lib/ext or any other
directory specified by the java.ext.dirs system property). It is implemented by the
sun.misc.Launcher$ExtClassLoader class.
The system class loader loads code found on java.class.path, which maps to the system CLASSPATH variable. This
is implemented by the sun.misc.Launcher$AppClassLoader class.