Reading from files in Java

There are several different ways to read input from a text file, including the use of Scanners along with their various "next" methods, such as nextInt(). (There's a good explanation of this at https://docs.oracle.com/javase/tutorial/essential/io/scanning.html.) Here is an example of a somewhat old-fashioned approach that has the advantage of working from within an application or an applet. The "StreamTokenizer" parses the contents of the input file into "tokens", which are basically words--sequences of characters delineated by whitespace. (By the way, the method outlined here does not use FileReaders, a technique outlined in most introductory Java textbooks. The Resource technique is what allows programs to run correctly both from within Java apps and applets.)

In the code below foo must be an instance of a user-defined class (i.e., a class that you have written, not a system-provided class.) If this code was in a public, non-static method, you could omit the "foo".

try 
   { 
   //create file input stream. Note that foo must a member of a user-defined class

   InputStream inS = foo.getClass().getResourceAsStream("input.txt");    
   if (inS == null) {
     System.out.println("File not found: input.txt"); 
     return;
   }
   // A Reader reads input as characters, rather than raw data.
   BufferedReader buffR = new BufferedReader(new InputStreamReader(inS));
   //The stream tokenizer parses the characters into words, integers, etc.
   StreamTokenizer in = new StreamTokenizer(buffR);

   in.nextToken(); // Get the first token. (A token can be a word, a number,    EOF, etc.)
   while (in.ttype != in.TT_EOF) // Keep going until exhausting tokens 
   { 
     if (in.ttype == in.TT_WORD) {
       if (in.sval.equals("JOB")) {
         ... }
       ...}

   in.nextToken(); // Get the next token 
   } 
} // yrt 
catch (IOException ex){ 
   System.out.println(ex.getMessage()); 
} 
finally { 
   try { 
     if (inS != null) inS.close(); 
   } 
   catch (IOException ex) 
   { 
     System.err.println("Had trouble closing input.txt.");
   } 
}