Java environment includes a large number of development tools and hundreds of classes and methods.

The development tools are part of the system known as Java Development Kit (JDK) and the class and methods are part of the Java Standard Library JSL) also known as the Application Programming Interface (API)

java environment

Java Development kit

Java Development Kit comes with a collection of tools that are used for developing and running java programs. they include

  • appletviewer (for viewing Java applets)
  • javac (java compailer)
  • java (Java interpreter)
  • Javap (Java disassembler)
  • Javah (for C header files)
  • Javadoc (for creating HTML documents)
  • Jdb (java debugger)
appletviewerEnables us to run Java applets (without actually using a Java-compatible browser)
javaJava interpreter, which runs applets and applications by reading and interpreting bytecode files
javacThe Java compiler, which translates Java sourcecode in bytecode files that the interpreter can understand
javadocCreate HTML format documentation from Java source code files
javahProduces header files for use with native methods
javapJava disassembler, which enables us to convert bytecode files into a program description
jdbJava debugger which helps us to find errors in our program.

The way these tools are applied to build and run application programs is illustrated To create a Java program,

we need to create a source code file using a text editor. The source code le then compiled using the Java compiler javac and executed using the Java interpreter java.

The Java debugger jdb is used to find errors, if any, in the source code. A compiled Java program can be converted into a source code with the help of the Java disassembler javap.

We learn more about these tools as we work through the book.

java envirnment

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Application Programming Interface

The Java Standard Library (or API) includes hundreds of classes and methods grouped into several functional packages (see Appendix G). The most commonly used packages are:

  1. Language Support Package: A collection of classes and methods required for implementing basic features of Java
  2. Utility Package: A collection of classes to provide utility functions such as the date and time functions.
  3. Input/Output Package: A collection of classes required for input/output manipulation.
  4. Networking Package: A collection of classes for communicating with other computers via the Internet.
  5. AWT Package: The Abstract Window Tool Kit package contains classes that implement a platform-independent graphical user interface.
  6. Applet Package: This includes a set of classes that allows us to create Java applets.

Java Runtime Environment

The Java Runtime Environment (JRE) facilitates the execution of programs developed in Java It primarily comprises the following:

  1. Java Virtual Machine (JVM): It is a program that interprets the intermediate Java byte code and generates the desired output. It is because of byte code and JVM concepts that programs written in Java are highly portable.
  2. Runtime class libraries: These are a set of core class libraries that are required for the execution of Java programs.
  3. User interface toolkits: AWT and Swing are examples of toolkits that support varied input methods for the users to interact with the application program.
  4. Deployment technologies: JRE comprises the following key deployment technologies:
    1. Java plug-in: Enables the execution of a Java applet on the browser.
    2. Java Web Start: Enables remote deployment of an application. With Web Start, users can launch an application directly from the Web browser without going through the installation procedure