What is -Xlint in compiling java program?why this is done?

[annamaneni sampath]

when i compile my sql program. i come across these error please help me
\\code
public class main {
^
Note: C:\Users\Admin\Desktop\MySQLAccess.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
1 error
\\code

[Mohamed Sanaulla]

From the javac page-

-deprecation
Show a description of each use or override of a deprecated member or class. Without -deprecation, javac shows a summary of the source files that use or override deprecated members or classes. -deprecation is shorthand for -Xlint:deprecation.

can you show us the code? You have used some deprecated methods or classes due to which the compiler is suggesting to compile with the deprecation option so that you can remove these deprecated usages. Deprecated code is the one that would be removed in the next release of JDK.

[annamaneni sampath]

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;

public class MySQLAccess {
	private Connection connect = null;
	private Statement statement = null;
	private PreparedStatement preparedStatement = null;
	private ResultSet resultSet = null;

	public void readDataBase() throws Exception {
		try {
			// This will load the MySQL driver, each DB has its own driver
			Class.forName("com.mysql.jdbc.Driver");
			// Setup the connection with the DB
			connect = DriverManager
					.getConnection("jdbc:mysql://localhost/feedback?"
							+ "user=sqluser&password=sqluserpw");

			// Statements allow to issue SQL queries to the database
			statement = connect.createStatement();
			// Result set get the result of the SQL query
			resultSet = statement
					.executeQuery("select * from FEEDBACK.COMMENTS");
			writeResultSet(resultSet);

			// PreparedStatements can use variables and are more efficient
			preparedStatement = connect
					.prepareStatement("insert into  FEEDBACK.COMMENTS values (default, ?, ?, ?, ? , ?, ?)");
			// "myuser, webpage, datum, summery, COMMENTS from FEEDBACK.COMMENTS");
			// Parameters start with 1
			preparedStatement.setString(1, "Test");
			preparedStatement.setString(2, "TestEmail");
			preparedStatement.setString(3, "TestWebpage");
			preparedStatement.setDate(4, new java.sql.Date(2009, 12, 11));
			preparedStatement.setString(5, "TestSummary");
			preparedStatement.setString(6, "TestComment");
			preparedStatement.executeUpdate();

			preparedStatement = connect
					.prepareStatement("SELECT myuser, webpage, datum, summery, COMMENTS from FEEDBACK.COMMENTS");
			resultSet = preparedStatement.executeQuery();
			writeResultSet(resultSet);

			// Remove again the insert comment
			preparedStatement = connect
			.prepareStatement("delete from FEEDBACK.COMMENTS where myuser= ? ; ");
			preparedStatement.setString(1, "Test");
			preparedStatement.executeUpdate();

			resultSet = statement
			.executeQuery("select * from FEEDBACK.COMMENTS");
			writeMetaData(resultSet);

		} catch (Exception e) {
			throw e;
		} finally {
			close();
		}

	}

	private void writeMetaData(ResultSet resultSet) throws SQLException {
		// 	Now get some metadata from the database
		// Result set get the result of the SQL query

		System.out.println("The columns in the table are: ");

		System.out.println("Table: " + resultSet.getMetaData().getTableName(1));
		for  (int i = 1; i<= resultSet.getMetaData().getColumnCount(); i++){
			System.out.println("Column " +i  + " "+ resultSet.getMetaData().getColumnName(i));
		}
	}

	private void writeResultSet(ResultSet resultSet) throws SQLException {
		// ResultSet is initially before the first data set
		while (resultSet.next()) {
			// It is possible to get the columns via name
			// also possible to get the columns via the column number
			// which starts at 1
			// e.g. resultSet.getSTring(2);
			String user = resultSet.getString("myuser");
			String website = resultSet.getString("webpage");
			String summery = resultSet.getString("summery");
			Date date = resultSet.getDate("datum");
			String comment = resultSet.getString("comments");
			System.out.println("User: " + user);
			System.out.println("Website: " + website);
			System.out.println("Summery: " + summery);
			System.out.println("Date: " + date);
			System.out.println("Comment: " + comment);
		}
	}

	// You need to close the resultSet
	private void close() {
		try {
			if (resultSet != null) {
				resultSet.close();
			}

			if (statement != null) {
				statement.close();
			}

			if (connect != null) {
				connect.close();
			}
		} catch (Exception e) {

		}
	}

}


public class main {
	public static void main(String[] args) throws Exception {
		MySQLAccess dao = new MySQLAccess();
		dao.readDataBase();
	}


}

[Matthew Brown]

I tried compiling that. Firstly I hit an error because main is a public class, so needs to be in its own file. That can be fixed just by removing the public, though.

Then, with -Xlint:deprecation added to the compiler arguments, you get this message:

warning: [deprecation] Date(int,int,int) in java.sql.Date has been deprecated
preparedStatement.setDate(4, new java.sql.Date(2009, 12, 11));

Looking at the Javadocs for java.sql.Date, you can see that the constructor that takes a year/month/day has been deprecated. You should use the other constructor that takes a long value. And you can construct the long value using the Calendar class. Something like:

Calendar c = Calendar.getinstance();
c.clear();
c.set(2009, 11, 11);
... new java.sql.Date(c.getTimeInMillis());

By the way, before you get caught up in the trap - your month value is 12. Months are zero-indexed in Java!

[Rob Spoor]

To be more precise, months are Calendar.JANUARY based. Now that happens to be 0, but it shows you that you should use Calendar.JANUARY, Calendar.FEBRUARY, ..., Calendar.DECEMBER instead of 0, 1, ..., 11. The latter will confuse people (they'll think 11 is November, not December), using Calendar.DECEMBER won't.

[Campbell Ritchie]

The tool lint is a long-established tool for finding errors and bugs in code. I don't know why it is called lint.

[fred rosenberger]

Campbell Ritchie wrote:The tool lint is a long-established tool for finding errors and bugs in code. I don't know why it is called lint.

The term was derived from the name of the undesirable bits of fiber and fluff found in sheep's wool.

--Wikipedia

[Matthew Brown]

Edit: too slow (and predictable)!

[Campbell Ritchie]

Thank you, both of you.

Fred rarely beats me . . . now, Rob Spoor, that's a different story.

[Rob Spoor]

It's my biggest hobby, beating Campbell. I especially like it when the difference is just a few seconds.

[Campbell Ritchie]

But very occasionally, I manage to get in before Rob

[Rob Spoor]

Usually when I'm off doing real work, instead of, well, being Campbell

[Campbell Ritchie]

Rob Spoor wrote: . . . well, being Campbell

Have you ever been Campbell?

[Rob Spoor]

I tried, but I didn't really like it

[Campbell Ritchie]

I tried it too, but seem to have liked it more than you.

[Rob Spoor]

I would definitely hope so!