1.  JAVA Compilation and Interpretation  JAVA Platform Independence  Building First JAVA Program  Escapes Sequences  Display text with printf  Data types in Java  Constants and Variables

2. Text Editor / IDE CompilerInterpreter Programmer Source Code.java file Byte Code.class file Hardware and Operating System Notepad, emacs,vi, Netbeans, Eclipse etc., javac java appletviewer

3. JAVA COMPILER JAVA BYTE CODE JAVA INTERPRETER WindowsMacintoshSolarisWindows NT (translator) (same for all platforms) (one for each different system)

4. Java Compiler - Java source code (file with extension.java) to bytecode (file with extension.class) Bytecode - an intermediate form, closer to machine representation A interpreter (virtual machine) on any target platform interprets the bytecode.

5. //This program prints Welcome to Java! public class Welcome { public static void main(String[] args) { System.out.printf(“%s”, “Welcome to Java!”); } //This program prints Welcome to Java! public class Welcome { public static void main(String[] args) { System.out.printf(“%s”, “Welcome to Java!”); } Welcome.java

6. //This program prints Welcome to Java! public class Welcome { public static void main(String[] args) { System.out.printf(“%s”, “Welcome to Java!"); } //This program prints Welcome to Java! public class Welcome { public static void main(String[] args) { System.out.printf(“%s”, “Welcome to Java!"); }  First line indicates comment. Which is not compiled by the JAVA  Public Specifies that the method is accessible from anywhere  Class is keyword and Welcome is a java identifier that specifies the name of the class to be defined.  Static is keyword, the main must always be declared as static since the interpreter uses this method before any objects are created.  Void is an modifier that states the main method does not return any value.  This is similar to the printf() statement of C.

8. System.out.printf  Feature added in Java SE 5.0  Displays formatted data  Format string  Fixed text  Format specifier – placeholder for a value  Format specifier %s – placeholder for a string System.out.printf( "%s\n%s\n", "Welcome to", "Java Programming!" );

9.  Although complex data values are represented using objects, Java defines a set of primitive types to represent simple data. Java provides eight primitive data types, they are  boolean  char, byte, short, int, long  float, double Primitive Data TypesSize in BytesSize in Bits int432 long864 float432 double864 char216 boolean (boolean in Java)18

10. A data type is defined by a set of values called the domain and a set of operations. The following table shows the data domains and common operations for all eight of Java’s primitive types: Type short int long float double char boolean 8-bit integers in the range –128 to 127 16-bit integers in the range –32768 to 32767 32-bit integers in the range –2146483648 to 2146483647 64-bit integers in the range –9223372036754775808 to 9223372036754775807 32-bit floating-point numbers in the range ± 1.4 x 10 -45 to ± 3.4028235 x 10 -38 64-bit floating-point numbers in the range ± 4.39 x 10 -322 to ± 1.7976931348623157 x 10 308 16-bit characters encoded using Unicode the values true and false The arithmetic operators: + - * / % add subtract remainder divide multiply = == = < != <= >= equal to less than greater or equal less or equal not equal > greater than The arithmetic operators except % The relational operators: The relational operators The logical operators: && add || or ! not DomainCommon operations byte

11.  The simplest terms that appear in expressions are constants and variables. The value of a constant does not change during the course of a program. A variable is a name for memory location, in which value can be stored this value may be changed at the time of execution.  Each variable has the following attributes:  A name, which enables you to differentiate one variable from another.  A type, which specifies what type of value the variable can contain.  A value, which represents the current contents of the variable.  A variable in Java is most easily envisioned as a box capable of storing a value. total 42

12.  In Java, you must declare a variable before you can use it. The declaration establishes the name and type of the variable and, in most cases, specifies the initial value as well. type name = value ;  The most common form of a variable declaration is where type is the name of a Java primitive type or class, name is an identifier that indicates the name of the variable, and value is an expression specifying the initial value. RULES: 1. First character should be an alphabet and remaining characters can be alpha-numeric. 2. Keywords cannot be used for defining. 3. No special symbols are allowed expect underscore and dollar. 4. Java is case sensitive, “Num” and “NUM” are different.