Object Life Cycle in Java

 An object typically goes through most of the following states between the time it is allocated and the time its resources are finally returned to the system for reuse.

1. Created
2. In use (strongly reachable)
3. Invisible
4. Unreachable
5. Collected
6. Finalized
7. Deallocated

Lets understand these in detail :

java SQL basics 3 : Understanding JDBC Drivers

JDBC drivers are divided into four types or levels. 

The different types of jdbc drivers are:
Type 1: JDBC-ODBC Bridge driver (Bridge)
Type 2: Native-API/partly Java driver (Native)
Type 3: AllJava/Net-protocol driver (Middleware)
Type 4: All Java/Native-protocol driver (Pure)

Type 1 JDBC Driver

JDBC-ODBC Bridge driver
The Type 1 driver translates all JDBC calls into ODBC calls and sends them to the ODBC driver. ODBC is a generic API. The JDBC-ODBC Bridge driver is recommended only for experimental use or when no other alternative is available.



Type 1: JDBC-ODBC Bridge

Advantage

The JDBC-ODBC Bridge allows access to almost any database, since the database's ODBC drivers are already available.

Disadvantages

1. Since the Bridge driver is not written fully in Java, Type 1 drivers are not portable.
2. A performance issue is seen as a JDBC call goes through the bridge to the ODBC driver, then to the database, and this applies even in the reverse process. They are the slowest of all driver types.
3. The client system requires the ODBC Installation to use the driver.
4. Not good for the Web.
let us learn more..

Java SQL basics 2 : Working with ResultSet Objects in JDBC.

IF you come here directly- you are suggested to read the article http://codingbasics.blogspot.com/2011/02/java-sql-basics-1-processing-sql.html

Updating Rows in ResultSet Objects

You cannot update a default ResultSet object, and you can only move its cursor forward.
However, you can create ResultSet objects that can be scrolled (the cursor can move backwards or move to an absolute position) and updated.

The following method, multiplies the PRICE column of each row by the argument percentage:

  public void modifyPrices(float percentage) throws SQLException {
    Statement stmt = null;
    try {
      stmt = con.createStatement();
      stmt = con.createStatement(
        ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
      ResultSet uprs = stmt.executeQuery(
        "SELECT * FROM " + dbName + ".COFFEES");


      while (uprs.next()) {
        float f = uprs.getFloat("PRICE");
        uprs.updateFloat("PRICE", f * percentage);
        uprs.updateRow();
      }


    } catch (SQLException e ) {
      JDBCTutorialUtilities.printSQLException(e);
    } finally {
      stmt.close();
    }
  }
The field ResultSet.TYPE_SCROLL_SENSITIVE creates a ResultSet object whose cursor can move both forward and backward relative to the current position
 and to an absolute position. The field ResultSet.CONCUR_UPDATABLE creates a ResultSet object that can be updated.

The method ResultSet.updateFloat updates the specified column (in this example, PRICE with the specified float value in the row where the cursor is positioned.
ResultSet contains various updater methods that enable you to update column values of various data types.
However, none of these updater methods modifies the database; you must call the method ResultSet.updateRow to update the database.
Learn about Batch Updates using Statement Objects

Java SQL basics 1 : Processing SQL statements with JDBC

In general, to process any SQL statement with JDBC, you follow these steps:

• Establishing a connection.
• Create a statement.
• Execute the query.
• Process the ResultSet object.
• Close the connection.

  public static void viewTable(Connection con, String dbName) throws SQLException {
    Statement stmt = null;
    String query = "select COF_NAME, SUP_ID, PRICE, SALES, TOTAL from " + dbName + ".COFFEES";
    try {
      stmt = con.createStatement();
      ResultSet rs = stmt.executeQuery(query);
      while (rs.next()) {
        String coffeeName = rs.getString("COF_NAME");
        int supplierID = rs.getInt("SUP_ID");
        float price = rs.getFloat("PRICE");
        int sales = rs.getInt("SALES");
        int total = rs.getInt("TOTAL");
        System.out.println(coffeeName + "\t" + supplierID + "\t" + price + "\t" + sales + "\t" + total);
      }
    } catch (SQLException e ) {
      JDBCTutorialUtilities.printSQLException(e);
    } finally {
      stmt.close();
    }


Lets break each step and understand the code