Here is a simple example to demonstrate how do connect to PostgreSQL database with JDBC driver in Java.

Go get a PostgreSQL JDBC driver first , else we can not do anything PostgreSQL JDBC Driver Download Here

Java JDBC connection always behave like following

Class.forName("org.postgresql.Driver");
Connection connection = null;
connection = DriverManager.getConnection(
"jdbc:postgresql://hostname:port/dbname","username", "password");
connection.close();

Here is the full example

import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.SQLException;
 
public class JDBCExample {
  public static void main(String[] argv) {
 
	  System.out.println("-------- PostgreSQL JDBC Connection Testing ------------");
 
	  try {
	    Class.forName("org.postgresql.Driver");
 
	  } catch (ClassNotFoundException e) {
	    System.out.println("Where is your PostgreSQL JDBC Driver? Include in your library path!");
	    e.printStackTrace();
	    return;
	  }
 
	  System.out.println("PostgreSQL JDBC Driver Registered!");
 
	  Connection connection = null;
 
	  try {
 
		 connection = DriverManager.getConnection("jdbc:postgresql://127.0.0.1:5432/testdb","mkyong", "123456");
 
	  } catch (SQLException e) {
	    System.out.println("Connection Failed! Check output console");
	    e.printStackTrace();
	    return;
	  }
 
	  if (connection != null)
		  System.out.println("You made it, take control your database now!");
	  else
	          System.out.println("Failed to make connection!");
	  }
}

How to run it?

Assume JDBCExample is store in c:\test folder, together with mysql JDBC driver

C:\test>java -cp c:\test\postgresql-8.3-603.jdbc4.jar;c:\test JDBCExample
-------- MySQL JDBC Connection Testing ------------
PostgreSQL JDBC Driver Registered!
You made it, take control your database now!
 
C:\test>