Core java
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This document summarizes key concepts about the Java programming language including: it was started in 1991 by Sun Microsystems, it is platform independent and portable, and focuses on classes, objects, methods and variables. Java code structure involves compiling Java files into bytecode that can be executed by a Java Virtual Machine. The document also outlines Java access modifiers, packages, and version history.
Core java
- 2. Started in the year 1991 Sun Micro Systems Java J2SE(Standalone Apps) J2EE(Web Apps) J2ME (Mobile Applications) Platform Independent Portable Secure
- 3. Basic Pascal Fortran C C++ Data Functions Functions Functions Functions Functions Functions Functions Functions
- 4. Continue… Java Programming language Class Methods Methods Data Methods Methods
- 6. The rules the compiler uses to determine whether a name is legal. Identifiers must start with a letter, a currency character ($), or a connecting character such as the underscore ( _ ). Identifiers cannot start with a number. After the first character, identifiers can contain any combination of letters, currency characters, connecting characters, or numbers. In practice, there is no limit to the number of characters an identifier can contain. You can't use a Java keyword as an identifier. Identifiers in Java are case-sensitive; foo and FOO are two different identifiers
- 8. Classes and Interfaces Ex: Dog, Account, PrintWriter,Runnable Methods Ex: getBalance, doCalculation, setCustomername Variables Ex:buttonWidth, accountBalance, myString Constants Ex: MIN_HEIGHT
- 9. Java 1.0 Java 1.1 Java 1.2 Java 1.3 Java 1.4 Java 1.5 Java 6 Java 7
- 10. Java program is usually a collection of objects talking to other objects by invoking each others methods Class Object State (instance variables) Behavior(Methods)
- 11. Code Structure in java Compilation and Execution is done with the help of the following commands javac Demo.java java Demo Demo.java Java Compiler Demo.class(Bytecode) JVM(JDK,JRE) Executable code
- 12. Code Structure in Java Class Dog { int size; String name; Instance Variables(state) String breed; public void bark() { System.out.println(“Dog barks”); Methods(Behaviour) } }
- 13. Package and Import statements Packages is a group of classes and interfaces. Package should be declared as the first statement in java Package statement should be followed by the import statements. Import statement is mainly used for accessing the in-built methods
- 14. Private Public Protected Default
- 15. Abstract Transient Final Static