$ javac TestInit2.java 
TestInit2.java:13: variable unknown might not have been initialized
        System.out.println(unknown);
                           ^
1 error

Code

import java.util.*;
import java.io.*;

public class TestInit2 {

    public static void main(String[] args){
        String unknown;
        try{
            unknown="cannot see me, why?";
        }catch(Exception e){
            e.printStackTrace();
        }
        System.out.println(unknown);
    }
}