问Android studio与postgresql的连接

EN

static final String JDBC_DRIVER = "org.postgresql.Driver";
    static final String DB_URL = "jdbc:postgresql://localhost:5432/user1";

//  Database credentials
static final String USER = "root";
static final String PASS = "root";

public static void main(String[] args)
{
    Connection conn = null;
    Statement st = null;
    try{
        //STEP 2: Register JDBC driver
        Class.forName("org.postgresql.Driver");

        //STEP 3: Open a connection
        System.out.println("Connecting to database...");
        conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/","root","root");

        //STEP 4: Execute a query
        System.out.println("Creating statement...");
        st = conn.createStatement();
        String sql;
        sql = "SELECT  first, last FROM Employees";
        ResultSet rs = st.executeQuery(sql);

        //STEP 5: Extract data from result set
        while(rs.next()){
            //Retrieve by column name
            String first = rs.getString("first");
            String last = rs.getString("last");

            //Display values
            System.out.print(", First: " + first);
            System.out.println(", Last: " + last);
        }
        //STEP 6: Clean-up environment
        rs.close();
        st.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(st!=null)
                st.close();
        }catch(SQLException se2){
        }// nothing we can do
        try{
            if(conn!=null)
                conn.close();
        }
        catch(SQLException se){
            se.printStackTrace();
        }//end finally try
    }
}