Capturar o valor de um Combobox

String  a = jComboBox1.getSelectedItem().toString();

import java.sql.Connection;


import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JComboBox;


public class MeuCombo extends JComboBox {
    private String sql;
    public  Statement st;
    public  ResultSet rs;
    public  Vector pks = new Vector();
    private Vector vetor = new Vector();
    public MeuCombo(String sql){
        super();
        this.sql = sql;
        setMaximumRowCount(10);
        preenche();
    }
   
    public void preenche(){
        try {
            //aqui colocar o codigo para preenchimento do combo e do vetor.
            Connection con = Conexao.abrirConexao();
            try {
             
                 st = con.createStatement();
                 rs = st.executeQuery(sql);
            } catch (Exception e) {
            }

            while (rs.next()) {
                addItem(rs.getString(2));
                
                pks.addElement(rs.getInt(1));
                pks.get(this.getSelectedIndex());
            }
        } catch (SQLException ex) {
           
        }
        
    }
//PreparedStatement psCombo = con.prepareStatement(sql);
    public void setValue(int chave) {
        
        // buscar no vetor o valor = chave e atribuir como item selecionado no combobox a posicao do vetor
    }
    
    public int getValue() {
       return 0; //pegar o numero do item selecionado no combo, pesquisar no vetor o mesmo numero e retornar o conteudo deste.
        
    }
}

MeuCombo jcEstado = new MeuCombo ("select cod_estado, sigla_estado from estado order by sigla_estado");

if (e.getSource()==jbOk){
            Habilita(true);
          // funçoes para inserir uma cidade no cadastro ***********

            String cod_estado = (String)jcEstado.getSelectedItem();
             cidade.setNome(tfNome.getText());
             cidade.setObs_Cid(tfObs.getText());
             cidade.inserirCidade();

/**
 * @author epinheiro - [email removido]
 * @author tribeiro - [email removido]
 *
 */
public class MobileCombo extends JComboBox {

	private static final long serialVersionUID = -5941046491248981373L;
	private Vector<ItemCombo> vectorItemCombo;
	
	public MobileCombo() {
		vectorItemCombo = new Vector<ItemCombo>();
	}
	
	public MobileCombo(Vector<ItemCombo> vectorItemCombo) {
		super(vectorItemCombo);
		this.vectorItemCombo = vectorItemCombo;
	}
	
	public void addItem(ItemCombo itemCombo) {
		super.addItem(itemCombo);
		vectorItemCombo.add(itemCombo);
	}

	public String getSelectedId() {
		return getSelectedItem() != null && ((ItemCombo) getSelectedItem()).getId() != null  
					? String.valueOf(((ItemCombo) getSelectedItem()).getId()) 
					: null;
	}
	
	public void setSelectedId(String id) {
		for (int i = 0; i < vectorItemCombo.size(); i++) {
			ItemCombo itemCombo = vectorItemCombo.get(i);
			if(String.valueOf(itemCombo.getId()).equals(id)) {
				setSelectedIndex(i);
				return;
			}
		}
		setSelectedIndex(0);
	}

	public String getSelectedValue() {
		return getSelectedItem() != null && ((ItemCombo) getSelectedItem()).getValue() != null  
		? ((ItemCombo) getSelectedItem()).getValue() 
		: null;
	}
	
	public void setSelectedValue(String value) {
		for (int i = 0; i < vectorItemCombo.size(); i++) {
			ItemCombo itemCombo = vectorItemCombo.get(i);
			if(itemCombo.getValue().equals(value)) {
				setSelectedIndex(i);
				return;
			}
		}
		setSelectedIndex(0);
	}
	
	public void insertItemAt(ItemCombo itemCombo, int index) {
		super.insertItemAt(itemCombo, index);
	}


	public void removeItem(ItemCombo itemCombo) {
		super.removeItem(itemCombo);
	}
	
	public Vector<ItemCombo> getItem(){
		return vectorItemCombo;
	}
	
	@Override
	public void removeAllItems() {
		vectorItemCombo.removeAllElements();
		super.removeAllItems();
	}
}

/**
 * @author Evandro
 * @author Thiago
 * 02/10/2008
 */
public class ItemCombo {
	private Integer id;  
	private	String value;

	public ItemCombo() {}
	
	public ItemCombo(Integer id, String value) {
		super();
		this.id = id;
		this.value = value;
	}

	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getValue() {
		return value;
	}
	public void setValue(String value) {
		this.value = value;
	}
	
	@Override
	public String toString() {
		return value;
	}
}

package combo;

import javax.swing.JComboBox;

public class MobileCombo extends JComboBox  {

	private static final long serialVersionUID = -5941046491248981322L;
	
	public void setSelectedId(int id) {
		for(int i = 0; i < getItemCount(); i++)
			if(id == ((ObjetoComID)getItemAt(i)).getId())
				setSelectedIndex(i);
	}
	
	public int getSelectedId() {
		return ((ObjetoComID)getSelectedItem()).getId();
	}
	
	public void setSelectedValor(String valor) {
		for(int i = 0; i < getItemCount(); i++)
			if(valor.equals(((ObjetoComID)getItemAt(i)).getValor()))
				setSelectedIndex(i);
	}
	
	public String getSelectedValor() {
		return ((ObjetoComID)getSelectedItem()).getValor();
	}
	
	public ObjetoComID getObjetoComID() {
		return (ObjetoComID)getSelectedItem();
	}
}

package combo;

public class ObjetoComID implements java.io.Serializable {

	private static final long serialVersionUID = 2502964297481251448L;
	
	private int id = 0;
	private String valor;
	
	public ObjetoComID() {
		super();
	}

	public ObjetoComID(int id, String valor) {
		this();
		setId(id);
		setValor(valor);
	}
	
	public int getId() {
		return id;
	}
	
	public void setId(int id) {
		this.id = id;
	}
	
	public String getValor() {
		return valor;
	}
	
	public void setValor(String valor) {
		this.valor = valor;
	}
}