conexão do mysql com java

private static Connection conexao =  null;

private static String url= “jdbc:mysql://localhost:3306/reflexao”;

private static String user = “root”, pass = “”;

public static Connection getConnection(){

try{	

Class.forName(“com.mysql.jdbc.Driver”).newInstance();

if( conexao == null){

conexao = DriverManager.getConnection(url,user,pass);

}

}

catch(Exception e){

//tratar erros…

}

return conexao;

}

package fontes;

import java.sql.*;

public class Conexao {
    
    private static Conexao instancia;
    private Connection conexao;
    
    private String servidor = "localhost";
    private String nomeBanco = "NOME_BANCOl";
    private String usuario = "SEU_USUARIO";
    private String senha = "SUA_SENHA";
    
    public static Conexao get() throws Exception {
        try {
            if (instancia == null){
                instancia = new Conexao();
            }
            return instancia;
        } catch(Exception e) {
            throw new Exception("Ocorreu um erro ao conectar com o banco de dados");
        }
    }
    
    public Conexao() throws Exception {
        Class.forName("com.mysql.jdbc.Driver").newInstance();
        conexao = DriverManager.getConnection("jdbc:mysql://"+servidor+"/"+nomeBanco, usuario, senha);
    }

private static Conexao instancia;
private Connection conexao;

private String servidor = "localhost";
private String nomeBanco = "sgcc";
private String usuario = "aluno";
private String senha = "aluno";

public static Conexao get() throws Exception {
    try {
        if (instancia == null){
            instancia = new Conexao();
        }
        return instancia;
    } catch(Exception e) {
        throw new Exception("Ocorreu um erro ao conectar com o banco de dados");
    }
}

public Conexao() throws Exception {
    Class.forName("com.mysql.jdbc.Driver").newInstance();
    conexao = DriverManager.getConnection("jdbc:mysql://"+servidor+"/"+nomeBanco, usuario, senha);
}
}

mport java.sql.*;

public class Conexao {

private static Conexao instancia;
private Connection conexao;

private String servidor = "localhost";
private String nomeBanco = "sgcc";
private String usuario = "aluno";
private String senha = "aluno";

public static Conexao get() throws Exception {
try {
if (instancia == null){
instancia = new Conexao();
}
return instancia;
} catch(Exception e) {
throw new Exception("Ocorreu um erro ao conectar com o banco de dados");
}
}

public Conexao() throws Exception {
Class.forName("com.mysql.jdbc.Driver").newInstance();
conexao = DriverManager.getConnection("jdbc:mysql://"+servidor+"/"+nomeBanco, usuario, senha);
}

 public static void main(String[] args) {

  Conexao conexao = new Conexao();
 
  conexao = get();
 
 }

}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
/**
 * @author  java_blues
 */
public class ConnectionFactory2 {
	static{
		try{
			Class.forName("com.mysql.jdbc.Driver");
		}
		catch(ClassNotFoundException e){
		        System.out.println(e.getMessage());
		        e.printStackTrace();
        }
	}
	
    private static Connection connection;
       
	public static Connection getConnection(String database, String user, String pass)throws SQLException{
		/*Se algum dia vc precisar de uma conexão remota basta trocar o localhost pelo IP
		e a porta do servidor separando-os com ':' sem aspas */
		connection = DriverManager.getConnection("jdbc:mysql://localhost/" + database, 											user, pass);
		
		
		return connection;
	}
}

import java.sql.*;
/**
*
* @author java_blues 
*/
public class ConnectionTester{
	private Connection conexao;
	private Statement stmt;
	private ResultSet rs;
	public void testaConexao()throws SQLException{
		try{
		/*Note que o metodo getConnection fornece conexões para qualquer banco do MySQL,
		bastando trocar os parametros */
			conexao = ConnectionFactory2.getConnection("sgcc","aluno","aluno");
			stmt = 	conexao.createStatement();
                        //use uma consulta sua
			rs = stmt.executeQuery("SELECT * FROM TABELA_ALUNOS");
			while(rs.next()){
                                //use um campo de sua tabela
				System.out.println(rs.getString("NOME_ALUNO"));
								
			}
		}
		catch(SQLException s){
			s.printStackTrace();
		}
		finally{
		/*Nao se esqueca de liberar os recursos do banco no bloco finally
		pois assim, aconteça o que acontecer não ficará nenhuma conexao 'pendurada' no banco
		
		*/
			rs.close();
			stmt.close();
			conexao.close();
		
		}
		
	}
	public static void main(String[] args){
		ConnectionTester teste = new ConnectionTester();
		try{
			teste.testaConexao();
		}
		catch(SQLException e){
			e.printStackTrace();
		}
		
	}
		
}

package fontes;

import java.sql.*;

public class Conexao {
    
    private static Conexao instancia;
    private Connection conexao;
    
    private String servidor = "localhost";
    private String nomeBanco = "SEU_BANCO";
    private String usuario = "SEU_USUARIO";
    private String senha = "SUA_SENHA";
    
    public static Conexao get() throws Exception {
        try {
            if (instancia == null){
                instancia = new Conexao();
            }
            return instancia;
        } catch(Exception e) {
            throw new Exception("Ocorreu um erro ao conectar com o banco de dados");
        }
    }
    
    public Conexao() throws Exception {
        Class.forName("com.mysql.jdbc.Driver").newInstance();
        conexao = DriverManager.getConnection("jdbc:mysql://"+servidor+"/"+nomeBanco, usuario, senha);
    }
    
    public static ResultSet ler(String sql) throws Exception {
        Statement st = Conexao.get().getConexao().createStatement();
        System.out.println(sql);
        ResultSet rs = st.executeQuery(sql);
        return rs;
    }
    
    public void atualizar(String sql) throws Exception {
        Statement st = Conexao.get().getConexao().createStatement();
        st.executeUpdate(sql);
        System.out.println(sql);
    }
    
    public java.sql.Connection getConexao() {
        return conexao;
    }
    
    
}

java.lang.NullPointerException

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at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel

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at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258

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at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL

istener.java:245)

at java.awt.Component.processMouseEvent(Component.java:5100)

at java.awt.Component.processEvent(Component.java:4897)

at java.awt.Container.processEvent(Container.java:1569)

at java.awt.Component.dispatchEventImpl(Component.java:3615)

at java.awt.Container.dispatchEventImpl(Container.java:1627)

at java.awt.Component.dispatchEvent(Component.java:3477)

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at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)

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    at java.awt.Window.dispatchEventImpl(Window.java:1606)
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    at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
    at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh

read.java:201)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre

ad.java:151)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
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