求一个JAVA应用系统能实现对数据库数据的增删改查就可以!谢谢

public class DbManager {
private Connection con;
private Statement stm;
public DbManager() {
try {
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
con = DriverManager.getConnection(
"jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=bbs",
"sa", "");

} catch (SQLException ex) {
System.out.println(ex.getMessage());
} catch (ClassNotFoundException ex) {
System.out.println(ex.getMessage());
}

}

public int exeSql(String sql) {

try {
stm = con.createStatement();
return stm.executeUpdate(sql);
} catch (SQLException ex) {
return 0;
}

}

public ResultSet query(String sql) {