/** 10/24/2018 */

public class ValueMethods
  /** This class shows return values from methods.
    * int, double, boolean
    * 
    * Method overloading - writing more than one method with the same
    * name. This is fine as long as the signature is different (i.e.
    * the parameter lists differ either in length or in type.)
    * Composition - calling a method inside a parameter to another method call
    */
{ 
 public static void main(String[]  args)
 {
  int sum=sum(123, 456); // assign the return value to a variable
  
  int num1=90, num2=333;
  System.out.println("sum of " + num1 + " and " + num2 + " is " 
                       + sum(num1,num2));
  // if you are using the return value later, then its better to
  // put it into a variable
  int ans = sum(num1, num2)*1000;  // call to sum(int,int)
  double sum2=sum(567.897, 432.12); // call to sum(double,double)
  System.out.println("sum of doubles: " + sum2);
  
  // calling boolean methods.
  // this simply prints true or false
  System.out.println("is " + num1 + " even? " + isEven(num1));
  // put return value in a variable to use later
  boolean even = isEven(num1);
  if (even)
    // do whatever pgm plans on doing with even numbers
    System.out.println(num1 + " is even!");
  // use the return value in an expression
  if (isValid(num1)) {
    System.out.println("num1 is valid " + num1);
  }
  if (!isValid(num2)) {
    System.out.println("num2 is NOT valid " + num2);
  }
  // Composition 
  sum = sum(num1, sum(num1, sum(num2, 100)));
  System.out.println("sum is now: " + sum);
 }
  /** method sum simply adds two ints and RETURNS the sum
   * @param x  first number to add
   * @param y second number to add
   * @return the sum of x+y
   */
 public static int sum(int x, int y) 
 {
   int sum=x+y;
   return sum;  // return expression
   // alternative:   return x+y;
 }
 
  /** method sum simply adds two doubles and RETURNS the sum
   * @param x  first number to add
   * @param y second number to add
   * @return the sum of x+y
   */
 public static double sum(double x, double y) 
 {
   return x+y;
 }
 /** method isValid tests whether the parameter is between 1 and 100
   * @param num an integer to check 
   * @return true if num is valid, false if num is invalid
   */
 public static boolean isValid(int num) 
 {
   if (num >=1 && num<=100)
       return true;
   return false;
   
   // alternatively
   // return num >=1 && num<=100;
 }
  /** method isEven tests whether the parameter is even or odd
   * @param num an integer to check 
   * @return true if num is even, false if num is odd
   */
 public static boolean isEven(int num) 
 {
   if (num%2 == 0)
       return true;
   return false;
   
   // alternatively
   // return num%2==0;
 }
}