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Null Pointer Exception: table Create USING MYSQL (If not exists")
Hi,
i have written a code to create a table 7 to insert data in it. However I am getting a null pointer Exception. Table already exist & "create table if not exists" doesnt seem to work. Some body please guide me.
This is my code:
import java.sql.*;
public class InsertCreate {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static String DB_URL = "jdbc:mysql://localhost/STUDENTS";
// Database credentials
static String USER = "root";
static String PASS = "";
//String sql="";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
String sql="";
try{
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(DB_URL,USER,PASS);
//creating table
sql = "CREATE TABLE if not exists REGISTRATION " +
"(id INTEGER not NULL, " +
" first VARCHAR(255), " +
" last VARCHAR(255), " +
" age INTEGER, " +
" PRIMARY KEY ( id ))";
System.out.println("SSSSSSSSSSSSS");
stmt.executeUpdate(sql); //ThIS LINE GIVING ERROR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
System.out.println("QQQQQQQQQQQQQ");
//inserting data
sql = "Insert into registeration values (1, 'first1', 'last1', 20)";
stmt.executeUpdate(sql);
//STEP 6: Clean-up environment
stmt.close();
conn.close();
}catch(SQLException se){
//Handle errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
}finally{
//finally block used to close resources
try{
if(stmt!=null)
stmt.close();
}catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end FirstExample
This is output of my program:
>javac InsertCreate.java
>java InsertCreate
SSSSSSSSSSSSS
java.lang.NullPointerException
at InsertCreate.main(InsertCreate.java:49)
Goodbye!
>
Somebody please guide me.
Zulfi.
Best Answer
-
Hi,
Thanks for your guidance. I have solved this problem. The correct code or creating table & inserting data into it is given below:
import java.sql.*;
public class InsertCreate {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static String DB_URL = "jdbc:mysql://localhost/STUDENTS";
// Database credentials
static String USER = "root";
static String PASS = "";
//String sql="";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
String sql="";
try{
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(DB_URL,USER,PASS);
stmt = conn.createStatement();
//creating table
sql = "CREATE TABLE if not exists REGISTRATION " +
"(id INTEGER not NULL, " +
" first VARCHAR(255), " +
" last VARCHAR(255), " +
" age INTEGER, " +
" PRIMARY KEY ( id ))";
System.out.println("SSSSSSSSSSSSS");
stmt.executeUpdate(sql);
System.out.println("QQQQQQQQQQQQQ");
//inserting data
sql = "Insert into registration values (2, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (3, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (4, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (5, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (6, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (7, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (8, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (9, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (10, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (11, 'first2', 'last2', 20)";
sql = "Insert into registration values (12, 'first2', 'last2', 20)";
sql = "Insert into registration values (14, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
System.out.println("RRRRRRRRRRRR");
//STEP 6: Clean-up environment
stmt.close();
conn.close();
}catch(SQLException se){
//Handle errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
}finally{
//finally block used to close resources
try{
if(stmt!=null)
stmt.close();
}catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end
Zulfi.
Answers
-
Statement stmt = null;
...
stmt.executeUpdate(sql);
must end up with null pointer exception (NPE).
-
Hi,
Thanks for your guidance. I have solved this problem. The correct code or creating table & inserting data into it is given below:
import java.sql.*;
public class InsertCreate {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static String DB_URL = "jdbc:mysql://localhost/STUDENTS";
// Database credentials
static String USER = "root";
static String PASS = "";
//String sql="";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
String sql="";
try{
//STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(DB_URL,USER,PASS);
stmt = conn.createStatement();
//creating table
sql = "CREATE TABLE if not exists REGISTRATION " +
"(id INTEGER not NULL, " +
" first VARCHAR(255), " +
" last VARCHAR(255), " +
" age INTEGER, " +
" PRIMARY KEY ( id ))";
System.out.println("SSSSSSSSSSSSS");
stmt.executeUpdate(sql);
System.out.println("QQQQQQQQQQQQQ");
//inserting data
sql = "Insert into registration values (2, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (3, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (4, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (5, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (6, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (7, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (8, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (9, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (10, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
sql = "Insert into registration values (11, 'first2', 'last2', 20)";
sql = "Insert into registration values (12, 'first2', 'last2', 20)";
sql = "Insert into registration values (14, 'first2', 'last2', 20)";
stmt.executeUpdate(sql);
System.out.println("RRRRRRRRRRRR");
//STEP 6: Clean-up environment
stmt.close();
conn.close();
}catch(SQLException se){
//Handle errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
}finally{
//finally block used to close resources
try{
if(stmt!=null)
stmt.close();
}catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
}catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end
Zulfi.