Simple string mistake

I am trying to create a string method in java where it prompts someone to enter a string longer than three characters. Once entered, I want to display the middle three characters of that string. Somet开发者_如何学Gohing is wrong because it is not compiling. Can anyone see my mistake? I can't find it. Thanks.

//MyString.java
import java.util.Scanner; 
 public class MyString .java {


    public static void main (String[] args) 
    {    

String string;


Scanner scan = new Scanner(System.in);
System.out.println ("Enter a string with a minimum of three characters: " + string); 
string = scan.nextLine();

System.out.println ("You entered: " + string);

String middle3;

System.out.println ("The middle three characters of the string: " + middle3);


    }


}

public class MyString .java {

this is wrong. remove ". java"

You are using MyString .java as the class name. Java does not allow space and period to be part of a valid class name. I guess you meant MyString.

Also variables string and middle3 are not initialized before their use.

You are not actually calculating middle3. It isn't even initialized to null. I imagine you want:

String middle3 = (string.length < 3) ? null : string.substring(string.length / 2 - 1), string.length / 2 + 2);

or something like that.

Why do you append string here?

 System.out.println ("Enter a string with a minimum of three characters: " + string ); 

here you should initialize middle:

String middle3 ="something";    
System.out.println ("The middle three characters of the string: " + middle3);