Problem s POstrgeSQL

Cau nejde mi spojeni s databazi

String url= new String("jdbc:postgresql://localhost:5432/postgres" );
Connection spojeni= DriverManager.getConnection(url,"postgres","a");

if (spojeni.isValid(10)) {
System.out.println("asdfasdf");
}
java.sql.Statement dotaz=spojeni.createStatement();
ResultSet co=dotaz.executeQuery("select * from sql_n");
int i=co.getInt(1);
System.out.println(Integer.toString(i)+"102");

A vyhodi to tuhle chybu

Exception in thread "main" java.sql.SQLException: No suitable driver found for jdbc:postgresql://localhost:5432/postgres
at java.sql.DriverManager.getConnection(DriverManager .java:602)
at java.sql.DriverManager.getConnection(DriverManager .java:185)
at ukazkapropojeni2.Main.main(Main.java:29)
Java Result: 1
BUILD SUCCESSFUL (total time: 2 seconds)