JDBC for postgresql 6.3.2.

Hi, guys:
   I tried to run the example programs for JDBC for postgresql 6.3.2,
but I got the error:
java.sql.SQLException: No suitable driver
java.sql.SQLException: No suitable driver       at java.sql.DriverManager.getConnection(DriverManager.java:111)
atjava.sql.DriverManager.getConnection(DriverManager.java:134)       at example.basic.<init>(basic.java:32)       at
example.basic.main(basic.java:166)
  Is there anybody can give me some hints how JDBC worked with 
postgresql 6.3.2?
  Thank you very much.
  mike