Tutorial Addendum On Java - Beheading Of Java Programs

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 31 December 18:00   

    



    



    

Execution Process

    



    

A Java appliance program is create of one or added classes and aught or added interfaces.

    

One of the chic must

    

have the main() adjustment as the beheading starting point of the program.

    

There are 3 accomplish complex in creating the classes and interfaces of a Java program,

    

and active the program:

    



        

  • Creating Classes and Interfaces: Creating a argument book for anniversary chic or

        

    interface that contains the analogue of the chic or interface accounting in Java

        

    language statements.

        

    Such a book is alleged antecedent cipher file, which haveto accept a book name identical to the

        

    name of the chic or interface authentic in the file, and an addendum of ".java".

        



  •     

  • Compiling Classes and Interfaces: Converting a antecedent cipher book into a bytecode

        

    file that contains the aforementioned analogue of the chic or interface accounting Java Basic

        

    Machine (JVM) instructions. A bytecode book haveto accept a book name identical to the

        

    name of the chic or interface authentic in the file, and an addendum of ".class".

        



  •     

  • Executing a Java Program: Loading bytecode files into JVM, and executing

        

    its JVM instructions starting from the access point of the defined class.

        



  •     



    



    

Creating a antecedent cipher book can be done by a simple argument editor, notepad, or a sophisticated

    

Java development ambiance tool, like Beheld J++.

    



    

Compiling a antecedent cipher book needs a Java compiler. The J2SDK amalgamation from Sun

    

Microsystems contains a Java compiler, which can be invoked by command "javac".

    

The "javac" command takes antecedent cipher book names as command band arguments. For

    

example, entering the afterward command in command window will adjure the "javac"

    

compiler to abridge the "Hello.java" antecedent cipher file:

    

 

    

c:j2sdk1.4.1_01injavac Hello.java

    



    



    

The "javac" command aswell has several command options available:

    



        

  • -d: Specify the agenda area the bytecode files generated by the compiler should

        

    be placed, if you don t wish to abode them in the accepted directory.

        



  •     

  • -classpath: Specify the directories area to seek for classes or interfaces

        

    definitions in bytecode format, if the classes or interfaces are acclimated in antecedent cipher file.

        



  •     

  • -sourcepatch: Specify the directories area to seek for classes or interfaces

        

    definitions in antecedent cipher format, if the classes or interfaces are acclimated in antecedent cipher file.

        



  •     



    



    

For example, the afterward command:

    

 

    

c:j2sdk1.4.1_01injavac -d .cls -classpath .lib;.cls

    

-sourcepath .src .srcTest.java

    



    



    

invokes the "javac" compiler, and tells it to:

    



        

  • Compile the "Test.java" antecedent cipher book in the ".src" directory.

        



  •     

  • Place the bytecode file, "Test.class", in the ".cls" directory.

        



  •     

  • Search ".lib" and ".cls" directories for the definitions in bytecode architecture

        

    of classes or interfaces that are acclimated in "Test.java".

        



  •     

  • Search ".src" agenda for the definitions in antecedent cipher architecture of classes

        

    or interfaces that are acclimated in "Test.java".

        



  •     



    



    

During the accumulation process, if the analogue of a chic or interface is acclimated

    

in the antecedent cipher file, the compiler will use the afterward rules to seek for

    

the definition:

    



        

  • If the compiler could not acquisition the chic or interface in the chic aisle and

        

    the antecedent path, the compiler will aftermath a accumulation absurdity adage

        

    that "cannot boldness symbol" area the attribute is the name of the chic or interface.

        



  •     

  • If the compiler acquisition the chic or interface alone in the chic path,

        

    the compiler will be blessed to use it as it is.

        



  •     

  • If the compiler acquisition the chic or interface alone in the antecedent path,

        

    the compiler will abridge it afore using it.

        



  •     

  • If the compiler acquisition the chic or interface in the antecedent aisle and in the chic path,

        

    the compiler will analyze the two file. If the antecedent cipher book is newer than

        

    the bytecode file, the compiler will abridge the antecedent cipher file.

        



  •     



    



    

Executing a Java program needs a JVM. The J2SDK aswell contains

    

a JVM, alleged HotSpot, which can be invoked by command "java".

    

The "java" command takes the name of the starting chic as the command

    

argument. For example, the afterward command:

    

 

    

c:j2sdk1.4.1_01injava -cp .lib;.cls;. Analysis

    



    



    

invokes HotSpot to:

    



        

  • Load "Test" chic into HotSpot.

        



  •     

  • Execute the main() adjustment of the "Test" class.

        



  •     



    



    

The "-cp" advantage defines the chic path, which contains directories area

    

the JVM will seek for the bytecode files of the starting chic and

    

other classes if needed.

    



    

 


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