![File Hello.java
1 public class Hello
2 {
3 public static void main(String[] args)
4 {
5 // display a greeting in the console window
6 System.out.println("Hello, World!");
7 }
8 }](https://image.slidesharecdn.com/zlcr5bg1qzrwn1xidphq-140524210928-phpapp01/85/Chapter-1-3-9-320.jpg)
![Java Program Structure
public class MyProgram
{
}
// comments about the class
public static void main (String[] args)
{
}
// comments about the method
method header
method body](https://image.slidesharecdn.com/zlcr5bg1qzrwn1xidphq-140524210928-phpapp01/85/Chapter-1-3-12-320.jpg)
Chapter 1.3
- 1. EXPLAINING THE PROGRAMMING PROCESS & TYPES OF ERRORS Chapter 1.3:
- 2. The Java Programming Language Created by Sun Microsystems, Inc. introduced in 1995 and it's popularity has grown quickly since Rich library Platform-independent ("write once, run anywhere") or architecture-neutral
- 3. Java Translation The Java compiler translates Java source code into a special representation called bytecode Java bytecode is not the machine language for any traditional CPU Another Java software tool, called an interpreter (or Java Virtual Machine (JVM)) , translates bytecode into machine language and executes it
- 4. Java Translation Java source code (program) Machine code Java bytecode Bytecode interpreter Java compiler
- 5. Portability After compiling a Java program into byte-code, that byte-code can be used on any computer with a byte-code interpreter and without a need to recompile. Byte-code can be sent over the Internet and used anywhere in the world. This makes Java suitable for Internet applications.
- 6. Becoming Familiar with your Computer to use Java Understand files and folders/directories Locate the Java compiler/ Install J2SE Set path & Java class path Write a simple program (later) Save your work Compile & run Use Dos Command Prompt or IDE
- 7. A DOS Command Window
- 9. File Hello.java 1 public class Hello 2 { 3 public static void main(String[] args) 4 { 5 // display a greeting in the console window 6 System.out.println("Hello, World!"); 7 } 8 }
- 10. Java Program Elements A Java program is made up of class definitions. A class definition must contains a header and a body. A class contains zero or more methods A method is a named section of code that also has a header & body A method contains program statements Single-line (starts with //) and multi-line (enclosed by /* and */) comments are used to document the code
- 11. Java Program Structure public class Hello { } // comments about the class class header class body //Comments can be placed almost anywhere
- 12. Java Program Structure public class MyProgram { } // comments about the class public static void main (String[] args) { } // comments about the method method header method body
- 13. Compiling and Running Type program into text editor Save (file name must be similar to class name) Open Dos Window Change directory to saved file directory Compile into byte codes javac Hello.java Execute byte codes java Hello
- 14. Processing a Java Program
- 15. Class Loader A Java program typically consists of several pieces called classes. Each class may have a separate author and each is compiled (translated into byte-code) separately. A class loader (called a linker in other programming languages) automatically connects the classes together and loads the compiled code (bytecode) into main memory.
- 16. Creating a Java Program… JVM Create/modify source code Source code Compile source code Byte code Run byte code Output Syntax errors Runtime errors or incorrect results
- 17. Errors It is common for programmer to make mistake in a program. Three kinds of errors Syntax errors Runtime errors Logic errors
- 18. Syntax Errors Grammatical mistakes in a program The grammatical rules for writing a program are very strict The compiler catches syntax errors and prints an error message. Example: using a period where a program expects a semicolon System.out.print("..."), System.out.print("Hello);
- 19. Runtime Errors Errors that are detected when your program is running, but not during compilation When the computer detects an error, it terminates the program and prints an error message. Example: attempting to divide by 0
- 20. Logic Errors Errors that are not detected during compilation or while running, but which cause the program to produce incorrect results Example: an attempt to calculate a Fahrenheit temperature from a Celsius temperature by multiplying by 9/5 and adding 23 instead of 32 E.g System.out.print("Hell");