Meaning of Null in Java and SQL code -

Meaning of Null in Java and SQL code -

hi i'm little bit confused code, want know if why value of object connection, resultset , preparedstatement null? can help me explain what's function of each code below? , why null?

public class loginform extends javax.swing.jframe { connection conn=null; resultset rs=null; preparedstatement pst=null; public loginform() { initcomponents(); conn = sqlconnnector.connectdb(); } }

they beingness set null explicit. alternative declare them this:

connection conn; resultset rs; preparedstatement pst;

either way statements doing allocating space in memory object. later initialized in line:

conn = sqlconnector.connectdb();

java