PostgreSQL:
String Driver="org.postgresql.Driver";    //?????????????
String URL="jdbc:postgresql://localhost/db_name";    //db_name????????
String Username="username";    //?????
String Password="password";    //????
Class.forName(Driver).newInstance();
Connection con=DriverManager.getConnection(URL??Username??Password);
DB2??
String Driver="com.ibm.db2.jdbc.app.DB2.Driver";    //???????DB2??????Provider???
//String Driver="com.ibm.db2.jdbc.net.DB2.Driver";    //?????????DB2??????Provider???
String URL="jdbc:db2://localhost:5000/db_name";    //db_name????????
String Username="username";    //?????
String Password="password";    //????
Class.forName(Driver).newInstance();
Connection con=DriverManager.getConnection(URL??Username??Password);
Informix:
String Driver="com.informix.jdbc.IfxDriver";
String URL="jdbc:Informix-sqli://localhost:1533/db_name:INFORMIXSER=myserver";    //db_name????????
String Username="username";    //?????
String Password="password";    //????
Class.forName(Driver).newInstance();
Connection con=DriverManager.getConnection(URL??Username??Password);
JDBC-ODBC:
String Driver="sun.jdbc.odbc.JdbcOdbcDriver";
String URL="jdbc:odbc:dbsource";    //dbsource????????
String Username="username";    //?????
String Password="password";    //????
Class.forName(Driver).newInstance();
Connection con=DriverManager.getConnection(URL??Username??Password);