Trying to understand the data flow in Java

Question

hi, I have been working on a project using s scheme client-server, I already create my class "server" and my class "client". I have these three lines:

1) Socket s=new Socket("127.0.0.1",5432);
2) ObjectInputStream in=new ObjectInputStream(s.getInputStream());
3) ObjectOutStream out=new ObjectOutputStream(s.getOutputStream());

The rare thing starts when the compiler gets to the second line and the program gets stuck, it doesn't carry on.
BUT when I change the order like this:

1) Socket s=new Socket("127.0.0.1",5432);
2) ObjectOutStream out=new ObjectOutputStream(s.getOutputStream());
3) ObjectInputStream in=new ObjectInputStream(s.getInputStream());

The program continues executing and does what it has to do
SO my question is: why is important to write the output first and then the input? otherwise, it will get stuck

Answer 1

Thank u very much, now I get it