Question

Why is it asking me to initialize the variable fin

FileInputStream fin;
File f = new File("C:/Users/NetBeansProjects/QuestionOne/input.txt");
fin = new FileInputStream(f);

When trying to close the file

fin.close();

Answer 1

I bet this is not exactly the same code that generated the compiler error. Almost sure you declared your variables outside the try-catch-finally block but you initialized them within the try block, which implies the variable may not be initialized in the context of the catch or finally blocks where the compiler error is occurring

For example:

FileInputStream fin;
try {
   File f = new File("C:/Users/NetBeansProjects/QuestionOne/input.txt");
   fin = new FileInputStream(f);
} finally {
   //you cannot be sure fin is initialized
   fin.close(); //compiler error
}

If you are using JDK 7 perhaps the best way is to use the try with resources to deal with the closing of your stream:

File f = new File("C:/Users/NetBeansProjects/QuestionOne/input.txt");
try(FileInputStream fin=new FileInputStream(f)) {
    //some input stream handlung here
}catch(IOException e){...}