R:\ap java\class slides\chapter 1\1 2 java development
- 1. Running a program Compiling A program, called a compiler , translates the source code into machine code The CPU then executes the machine code C, FORTRAN, Pascal, COBOL, BASIC Interpreting A program, called an interpreter, reads the source code and executes the instructions BASIC, LISP, Perl, Python
- 2. Java Code Execution Compiler (javac) translates source code (.java file) to byte code (.class file) Byte code is machine independent Byte code is interpreted by the Java run-time program program (java), the IDE (BlueJ), the appletviewer, or the web browser. The program can be compiled on one machine and interpreted on another.
- 3. Java Pyramid Application or Applet Class Class Project Data Methods Data Instructions
- 4. Java Development JDK 1.6.20 SE Development Kit (JDK) http:// java.sun.com/javase/downloads/index.jsp Includes compiler, interpreter, and libraries BlueJ Version 3 IDE (Integrated Development Environment) Tools for designing, developing, and testing Java software. http:// bluej.org
- 5. Hello, world!! Class Methods main Comments javadocs Blocks
- 6. Classes and Objects A class is a definition of a (complex) data type An object is an instantiation of a class A Java program is a set of interacting objects Everything in Java is an object
- 7. Special method: main Methods A collection of data and instructions Has a specific purpose public static void main(String args) The start of a Java application It must belong to a class (We will cover applets after we’ve covered objects and classes)
- 8. Comments Notes to other readers of your software (including your teacher and yourself). Ignored by the machine. Two formats: “/*” starts a comment, ‘*/’ finishes it. These comments can span multiple lines. ‘//’ starts the comment, EOL (end-of-line) finishes it. Comments can be inserted anywhere, but there are some common locations.
- 9. Blocks A section of code; a set of instructions or statements. A block starts with ‘{‘, and ends with ‘}’ Blocks are written for: Method definitions Class definitions Loops ‘then’ and ‘else’ bodies Blocks also define scope for variables.
- 10. Lab 0: Hello, world
- 11. Lab 0 debrief: What have we discovered? We created an application called Hello The software was created in a folder in My Documents also called Hello The folder has a file called Hello.java containing: A Class called Hello The main method, the applications starting point. The compiler creates a file called Hello.class containing the program’s byte code. We were able to do everything using BlueJ