1. JAVA PROGRAMING LANGUAGE

2. Content of Java 2 SDK  Development Tools (In the bin subdirectory.) Tools and utilities that will help you develop, execute, debug, and document programs written in the Java programming language. For further information, see the tool documentation.tool documentation  Runtime Environment (In the jre subdirectory.) An implementation of the Java 2 runtime environment for use by the SDK. The runtime environment includes a Java virtual machine, class libraries, and other files that support the execution of programs written in the Java programming language.  Additional Libraries (In the lib subdirectory.) Additional class libraries and support files required by the development tools.  Demo Applets and Applications (In the demo subdirectory.) Examples, with source code, of programming for the Java platform. These include examples that use Swing and other Java Foundation Classes, and the Java Platform Debugger Architecture.  C header Files (In the include subdirectory.) Header files that support native-code programming using the Java Native Interface, the Java Virtual Machine Debugger Interface, the Java Virtual Machine Profiler Interface and other functionality of the Java 2 Platform. Java Native InterfaceJava Virtual Machine Debugger InterfaceJava Virtual Machine Profiler Interface  Source Code (In src.zip.) Java programming language source files for all classes that make up the Java 2 core API (that is, sources files for the java.*, javax.* and some org.* packages, but not for com.sun.* packages). This source code is provided for informational purposes only, to help developers learn and use the Java programming language. These files do not include platform- specific implementation code and cannot be used to rebuild the class libraries. To extract these file, use any common zip utility. Or, you may use the Jar utility in the Java 2 SDK's bin directory: jar xvf src.zip

3. J2SE Directory Structure

4. Example / Demo  Helloworld  Applet

5. Language Basic  The BasicsDemo program adds the numbers from 1 to 10 and displays the result.  The output from this program is: Sum = 55  Basic demo program uses many of the traditional features of the Java programming language, including variables, operators, and control flow statements public class BasicsDemo { public static void main(String[] args) { int sum = 0; for (int current = 1; current <= 10; current++) { sum += current; } System.out.println("Sum = " + sum); }

6. Variable  Definition: A variable is an item of data named by an identifier.  The variable's name must be a legal identifier -- an unlimited series of Unicode characters that begins with a letter  We use the variable name to refer to the data that the variable contains  Variable declaration  Example : MaxVariableDemo  Scope : The section of code where the variable's simple name can be used. The variable's scope is determined implicitly by the location of the variable declaration, that is, where the declaration appears in relation to other code elements type name Ex: String kata, int bil

7. Variable Name  In the Java programming language, the following must hold true for a simple name: It must be a legal identifier. An identifier is an unlimited series of Unicode characters that begins with a letter. It must not be a keyword, a boolean literal (true or false), or the reserved word null.keyword It must be unique within its scope. A variable may have the same name as a variable whose declaration appears in a different scope. In some situations, a variable may share the same name as another variable if it is declared within a nested block of code. (We will cover this in the next section, Scope.)  By Convention : Variable names begin with a lowercase letter, and class names begin with an uppercase letter. If a variable name consists of more than one word, the words are joined together, and each word after the first begins with an uppercase letter, like this: isVisible. The underscore character (_) is acceptable anywhere in a name, but by convention is used only to separate words in constants (because constants are all caps by convention and thus cannot be case-delimited)

8. Keyword