CS 101 - 9/1/11

Chpt 2.  Java Langauge & DrJava Development Environment

Lab on Friday: Set up DrJava

Set up on a home/personal computer


java file set-up

Source Code Files:           .java
Java Byte Code File:         .class
DrJava Version Control File: .java~

Simple Output Statement:

  System.out.println ("Words to be output");

Comments - Information ignored by the compiler
    - added to help the humans looking at the program


  // - end of line comment

  /*     */  - Block Comment

  /**   */   - Special Block Comment for JavaDocs

Java Variables - names that are associated with 
      memory storage, the compiler associates a
      name with a "numbered mailbox" in the computer's
      memory

      types of value - speficies the encoding structure
         of the data

      int - positive or negative whole number (integer)
      double - floating point numbers (real numbers)
      char - character
      String - words, a group of characters
      boolean - true or false

      Variable declaration syntax

        int number1;

      names must begin with a letter and then can
        contain letters, digits or underscores

        double areaOfACircle;   // good style
        double area_of_a_circle;// good style
        double areaofacircle;   // bad style

    
     Assignment statement;

     number1 = 7;

     int number2, number3;

     number2 = number1;

     variable =  expression ;

     An Assignment stores the result of the expression
        into the variable

     number3 = number1 + 5;

     int counter = 0;

     number3  = 5 + (7 * 2);