Here are some basics about Java and BlueJ:
>>>Java is a high level language.
>>>Java requires JDK 1.2 or higher version environment to run the program.
>>>BlueJ and Greenfoot are Windows based software which are especially prepared for Java programs to write and to compile.
>>>JDK means Java Development Kit.
>>>BlueJ requires JDK 1.3 for its supplementary.
>>>Java is a simplified version of c and c++.
>>>Java does not support operator overloading.
>>>Java does not support multiple inheritance instead it supports hierarchy of inheritance.
>>>No header file are used in Java.Instead it header files,packages are imported in the programs.
>>>Java does not support pointers.
>>>Java files takes .java extension.
>>>When class is saved it take .CLA extension. this file is run to obtain the output.
>>>Class is declared by the keyword class.this class is compiled in JDK or BlueJ.
>>>Packages in Java contain various classes to simplify the work and provide vorious functions.
>>>Comments can be included in the program after //.
>>>Comments and identation in the programs makes them more understandable.
>>>Complexity makes a program bad.A program should have simplicity so that it may be understood very easily.
>>>A program should be written such as it could be modified as and when needed.
>>>A program should not be restricted to be used only on a single computer.It should have portability so that it could be used by the users.
>>>Modular approach of programming concentrates on breaking the program into a number of small programs.
>>>Modular programming does not use GOTO statement for calling modules by a module.
>>>A module is a small program which can be further divided into sub-programs.
>>>In modular programming,programs take more storage space because of number of modules,but the programs written in such an approach are easily understandable.
>>>A program having syntax error does not compile.
>>>Command to compile a java program is javac.
>>>Command to execute a compiled java program is java.
>>>The removal of errors in a program is called debbuging.
>>>Logical errors are the most difficult errors to locate in a program.
>>> // Symbol indicates that whatever follows after it are comments in a single line.
>>>Comments of more than one line can be given by enclosing them by /* and */ symbols.
>>>Blank lines and spaces inserted within a program to enhance readibility and clarity are termed as white spaces.
>>>Every java application has a main method that tells how and in what sequence other methods are used.
>>>Every statement should be terminated with the symbol ; in Java.
>>>Main window of BlueJ is called project window.
>>>In BlueJ the objects created are displaced in object bench.
>>>README.TXT file that appears on the class structure overview of BlueJ may be used for documenting the project.
>>>In BlueJ we enter the codes in Editor window.
>>>After entering the codes we need to compile the codes before executing programs.
>>>After executing the main method, the output appears on the Terminal Window of BlueJ.
Hope this may help you in learning some basic information about Java Programming Language. However you can also visit Programming Zone of Techno Geek Zone to learn about some programs of Java.