Files Review For output to a file: –FileOutputStream variable initialized to filename (String) and append/not append (boolean) –PrintWriter variable initialized to FileOutputStream variable For input from file: –File variable initialized to filename (String) –Scanner variable initialized to File variable

import java.util.Scanner; import java.io.*; class FormatFileData { public static void main(String [ ] args) throws IOException { int loops, integer, i; float decimal; String name; File ifile = new File("mydata.txt"); Scanner scan = new Scanner(ifile); loops = scan.nextInt(); for(i= 0 ; i < loops; i++) { integer = scan.nextInt(); decimal = scan.nextFloat(); name= scan.next(); System.out.print(integer + " "); System.out.print(decimal + " "); System.out.print(name + " "); System.out.println(); } mydata.txt file Jon Bill e9 Mary Smith -3 -4e3 xyz Jon Bill E10 Mary Smith -3 – xyz Output:

Determining End of File There is a scan.hasNext() in JAVA Not used to determine if there is a String Used to Detect End of File (EOF), i.e., there is nothing left to read in the file Returns false if at EOF

Methods public static void main(String [] args) { … displayVals(); … displayVals(); … displayVals(); return(0); } public static void displayVals() { System.out.println(…); return; /*back to where we left off */ }

Methods Method: A Discrete Piece of Code that Performs a Specific Operation or Task Named with a Descriptive Identifier Called from main() or Another Method When Called, Program Control (Execution) Is Transferred to the method Method Performs Required Tasks, and then Possibly Returns a Value After Return from Method, Control Returns to the Statement Following the Method Call

Method Attributes Method Name: Identifier Used to Call method Method Parameter(s) or Argument(s): Value(s) Passed into method for Use by method Code Method Return Value: Value Returned by method Back to Calling method

Method Parameters (Arguments) May Pass as Many Parameters as Necessary to method A Copy of the Value of the Parameter Is Passed to the Method Changing the Value of the Parameter in the Method Does Not Affect the Value of the Original Variable This Is Called Pass-by-Value

Methods – Return Values Methods Are Typed According to Their Return Values: void, int, double, etc. Method Returns a Value to Calling method via return Statement

public static void main(String [ ] args) { int val = 9,resultSq; resultSq = squareVal(val); System.out.println(“squareVal returned: " + resultSq); resultSq = squareVal(12); } public static int squareVal(int numToSq) { System.out.println("In squareVal "); return(numToSq * numToSq); }