java.lang.NullPointerException jdbc big error

Question

I new in java programing, so I have one big error which I cannot solve:

Here is stack trace of the exception:

java.lang.NullPointerException
    at com.smy.gome.MySQL.checkUser(MySQL.java:56)
    at com.smy.gome.LogReg$1.actionPerformed(LogReg.java:43)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

My code at MySQL.java:56

Here is the Java code:

ResultSet user = statement.executeQuery("SELECT * FROM tadzio WHERE nick='benas12' AND pass='benas'");

MySQL.java:

package com.smy.gome;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class MySQL {

    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
    static final String DB_URL = "jdbc:mysql://localhost/root";

    static final String USER = "root";
    static final String PASS = "benux1";

    public static Connection conn = null;
    public static Statement statement = null;
    public static ResultSet results = null;

    public synchronized static void Connection(){
        try{
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            conn = DriverManager.getConnection("jdbc:mysql://localhost/root", "root", "benux1");
        }catch(Exception e) {
            e.printStackTrace();
        }
    }

    public synchronized static void Destroy(){
        try {
            statement.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public synchronized static ResultSet query(String s) throws SQLException {
        try {
            if (s.toLowerCase().startsWith("select")) {
                ResultSet rs = statement.executeQuery(s);
                return rs;
            } else {
                statement.executeUpdate(s);
            }
            return null;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static int checkUser() {
        try {
            conn.createStatement();
            ResultSet user = statement.executeQuery("SELECT * FROM tadzio WHERE nick='benas12' AND pass='benas'");
            user.next();
            int count = user.getRow();
            return count;
        } catch(Exception e) {
            e.printStackTrace();
            return -1;
        }
    }

    public static String getVersion(){

        return "tadis";
    }

}

Thanks for helping me

did u create a statement before line 56 .. i.e. do u have line like createStaetment() or prepareStatement() etc... — Pavan Kumar K, Jul 02 '15 at 10:26
Post some piece of code with this stack trace. It will be helpful :) — Aleksandar, Jul 02 '15 at 10:32
Make sure that 'statement' object is 'not null' .Get the connection object,Create statement object throug the connection then use statement object to query. — Mihir, Jul 02 '15 at 10:33
You need to add relevant code for people to actually help you. Also, kindly search for similar issues faced by other people, here or google it. I am sure NullPointerException will have a lot of questions and answers on SO itself. — Ritikesh, Jul 02 '15 at 10:33
You need to add the code where you declare and initialize `statement`. — Jurgen Camilleri, Jul 02 '15 at 10:49
@Smygolas you may accept the working answer/post. It helps others in future — JavaHopper, Jul 02 '15 at 11:21

score 0 · Answer 1 · answered Jul 02 '15 at 10:53

0

You are not assigning statement. Change the code to the below:

public static int checkUser() {
    try {
        statement = conn.createStatement();
        ResultSet user = statement.executeQuery("SELECT * FROM tadzio WHERE nick='benas12' AND pass='benas'");
        user.next();
        int count = user.getRow();
        return count;
    } catch(Exception e) {
        e.printStackTrace();
        return -1;
    }
}

answered Jul 02 '15 at 10:53

Jurgen Camilleri

3,559
20
45

This code not working for me. – Smygolas Jul 02 '15 at 10:56
You need to be a bit more specific than that. – Jurgen Camilleri Jul 02 '15 at 10:57
@JurgenCamilleri he is using `statement` at various other places. @Smygolas use the code present in my answer. It should hopefully work. If some other error crops up, please share the stack trace – JavaHopper Jul 02 '15 at 11:02

JavaHopper · Accepted Answer · 2015-07-02T11:12:06.313

Its resulting from statement being null

For entire code to work as expected, use following code, because statement is being used at various places

package com.smy.gome;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class MySQL {

    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
    static final String DB_URL = "jdbc:mysql://localhost/root";

    static final String USER = "root";
    static final String PASS = "benux1";

    public static Connection conn = null;
    public static Statement statement = null;
    public static ResultSet results = null;

    public synchronized static void Connection(){
        try{
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            conn = DriverManager.getConnection("jdbc:mysql://localhost/root", "root", "benux1");
            statement = conn.createStatement();
        }catch(Exception e) {
            e.printStackTrace();
        }
    }

    public synchronized static void Destroy(){
        try {
            statement.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public synchronized static ResultSet query(String s) throws SQLException {
        try {
            if (s.toLowerCase().startsWith("select")) {
                ResultSet rs = statement.executeQuery(s);
                return rs;
            } else {
                statement.executeUpdate(s);
            }
            return null;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static int checkUser() {
        try {
            ResultSet user = statement.executeQuery("SELECT * FROM tadzio WHERE nick='benas12' AND pass='benas'");
            user.next();
            int count = user.getRow();
            return count;
        } catch(Exception e) {
            e.printStackTrace();
            return -1;
        }
    }

    public static String getVersion(){

        return "tadis";
    }

}

`conn.CreateStatement();` should be removed from `checkUser()` then. — Jurgen Camilleri, Jul 02 '15 at 11:08
@JurgenCamilleri thanks for pointing out, I agree!! Edited accordingly — JavaHopper, Jul 02 '15 at 11:12
stack trace and line number please. Also, did you compile the MySQL.java file again, before running? — JavaHopper, Jul 02 '15 at 11:41
@Smygolas up vote if its working :) Today is gonna be my day here at stackoverflow (being greedy for reputation and my score) — JavaHopper, Jul 02 '15 at 12:08

java.lang.NullPointerException jdbc big error

2 Answers2