表和数据：

CREATE TABLE weather (
    city            varchar(80),temp_lo         int,-- low temperature
    temp_hi         int,-- high temperature
    prcp            real,-- average temperature
    date            date
);

insert into weather values ('Wuhan',15,30,25.5,'2010-09-21');
insert into weather values ('Beijing',10,22,15.3,'2010-09-22');
insert into weather values ('Shanghai',17,35,28.6,'2010-09-22');
insert into weather values ('Guangzhou',36,32.7,'2010-09-22');
insert into weather values ('Xiamen',24,32,30.3,'2010-09-22');

public class TestConnPostgresql {

	public static void main(String[] args) {
		try {
			Class.forName("org.postgresql.Driver").newInstance();
			String url = "jdbc:postgresql://localhost:5432/testdb";
			Connection conn = DriverManager.getConnection(url,"postgres","postgres");
			
			Statement st = conn.createStatement();
			String sql = "select * from weather";
			ResultSet rs = st.executeQuery(sql);
			while(rs.next()){
				System.out.print( rs.getString("city") + "\t");
				System.out.print( rs.getString("temp_lo") + "\t");
				System.out.print( rs.getString("temp_hi") + "\t");
				System.out.print( rs.getString("prcp") + "\t");
				System.out.println( rs.getString("date"));
			}
			
			rs.close();
			st.close();
			conn.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}