CLASSPATH in JAVA

CLASSPATH: CLASSPATH describes the location where the required “.class files” are available. 
 Then JVM uses CLASSPATH to locate required .class files.

 We can set the CLASSPATH in the following 3 ways.

  1. By using environment variable CLASSPATH (in WINDOWS),by updating .bashrc (in LINUX/UNIX).

     This CLASSPATH will be preserved even after system restart aslo. Hence this is permanent way of setting CLASSPATH.

Identifiers in Java

Identifier:

•   In java identifier defined as either class name or interface name or package name or method name or variable name or block name.

•   An identifier is a sequence of one or more characters. The first character must be a valid first character (letter, $, _).
• It allows a programmer to refer to the item from other places in the program.

Example:

package in.blogspot.java2bigdata;
class Identifier1{
int identifier2 =10;
static{
System.out.println("inside static block");
}
public void identifier3(){
}
}

In the above example class name as Idnetifier1,variable name as identifer2, package name as in.blogspot.java2bigdata and method name as identifier3() are considered as Identifiers.

Understanding the directory structure of JDK (Java SDK)

In this artical ,We will discuss about the directory structure of JDK(Java Development kit) .

Generally JRE(Java Runtime Environment) is installed with JDK so here we are discussing about the both of JDK and JRE directory and file structure. The file structure of JRE is identical to that of the JDK's JRE directory.

General files and Directories

Learn Oracle SQL Query Writing Within couple of Hours

Learn General Oracle/SQL Query Writing :

Quick Reference Oracle SQL Query writing. Go through this post and learn Oracle SQL writing within couple of hours. Quick reference Oracle DML,DDL,DCL Operations.

SELECT Retrieves data from the database.

INSERT ,UPDATE,DELETE,MERGE

Enters new rows, changes existing rows, and removes unwanted rows from tables in the database, respectively. Collectively known as data manipulation language (DML).

CREATE, ALTER ,DROP

RENAME

TRUNCATE

Sets up, changes, and removes data structures from tables. Collectively known as data

Definition language (DDL).

COMMIT

ROLLBACK

SAVEPOINT

Manages the changes made by DML statements. Changes to the data can be grouped together into logical transactions.

GRANT

REVOKE