Interpreters & Debuggers...Overview of Interpreters,Debuggers..Process of Building and Running Java Programs

1. CHAPTER-8
Interpreters
&
Debuggers

2. Interpreters
Impure Interpreter performs some preliminary processing of source program to reduce
the analysis overheads during interpretation

3. • Overview of Interpretation

4. • Benefits of Interpretation
• An interpretive language is relatively easy to
code, test, and change
• Good for one-time solutions
• Good for developing application prototypes
• Time saver for command strings that are
entered repeatedly

5. •Java Language Enviornment
•
Java Development Kit
• javac - The Java Compiler
• java - The Java Interpreter
• jdb- The Java Debugger
• appletviewer -Tool to run the applets
• javap - to print the Java bytecodes
• javaprof - Java profiler
• javadoc - documentation generator
• javah - creates C header files

6. Process of Building and Running Java
Programs
Text Editor
Java Source
Code
javac
Java Class File
java
Output
javadoc
javah
jdb
HTML Files
Header Files

7. Java virtual machine (JVM)
• It is an abstract computing machine that enables a
computer to run a Java program.
• There are three notions of the JVM: specification,
implementation, and instance.
• The specification is a document that formally describes
what is required of a JVM implementation. Having a
single specification ensures all implementations
are interoperable.
• A JVM implementation is a computer program that
meets the requirements of the JVM specification.
• An instance of a JVM is an implementation running in
a process that executes a computer program compiled
into Java bytecode

8. Class Loader
• One of the organizational units of JVM bytecode is a class. A
class loader implementation must be able to recognize and
load anything that conforms to the Java class file format.
• The class loader performs three basic activities in this strict
order:
1. Loading: finds and imports the binary data for a type
2. Linking: performs verification, preparation, and (optionally)
resolution
– Verification: ensures the correctness of the imported type
– Preparation: allocates memory for class variables and
initializing the memory to default values
– Resolution: transforms symbolic references from the type
into direct references.
3. Initialization: invokes Java code that initializes class variables to
their proper starting values.

9. •Java Virtual Machine(JVM)  JVM is a software emulation of a hypothetical computing
machine that runs Java bytecodes (Java compiler output)
Java Run-Time System
Byte
Code
Verifier
Class
Loader
Interpreter
Just-in-time
Compiler
Java
Runtime
Hardware

10. •Java Virtual Machine(JVM) JVM is a software emulation of a hypothetical computing
machine that runs Java bytecodes (Java compiler output)
Java Run-Time System
Byte
Code
Verifier
Class
Loader
Interpreter
Just-in-time
Compiler
Java
Runtime
Hardware