//This file has several exmaples of methods being used on 
// an array of primes

import java.util.*;

public class PrimesArray {
   public static void main(String[] args){
      int[] primes = {2, 3, 5, 7, 11, 13, 17, 19, 23};
      
      // find the sum of the array elements and print it
      int sumOfPrimes = sum(primes);
      System.out.println("Sum was: " + sumOfPrimes);
      System.out.println();
      
      //printing
      System.out.println("Printing the array");
      // not good default printing
      System.out.println(primes); 
      // custom printing method
      printArray(primes); 
      // Java util helper method for printing
      System.out.println(Arrays.toString(primes)); 
      System.out.println();
      
      // reverse
      System.out.println("Reversing the array");
      reverse(primes);
      System.out.println(Arrays.toString(primes));
      System.out.println();
      
      // evil print (it changes the array when it prints it)
      System.out.println("Evil print");
      evilPrintArray(primes);
      evilPrintArray(primes);
   }
   
   // This method takes an int[] and finds the sum of all the
   // elements. It returns the sum.
   public static int sum(int[] a){
      int sum = 0;
      for(int i = 0; i < a.length; i++){
         sum += a[i];
      }
      return sum;
   }
   
   // This method takes an int[] and prints it out.
   public static void printArray(int[] a){
      System.out.print("[" + a[0]);
      for(int i = 1; i < a.length; i++){
         System.out.print(", " + a[i] );
      }
      System.out.println("]");
   }
   
   // This method takes an int[] and prints it out.
   // It also, unexpectedly, changes the array it was given.
   public static void evilPrintArray(int[] a){
      System.out.print("[" + a[0]);
      for(int i = 1; i < a.length; i++){
         System.out.print(", " + a[i] );
      }
      System.out.println("]");
      a[0] = -32847;
   }
   
   // This method takes an int[] and reverses the elements in
   // the array. It doesn't return anything since it modifies
   // the array that was passed in.
   public static void reverse(int[] a){
      for(int i = 0; i < a.length / 2; i++){
         int temp = a[i];
         a[i] = a[a.length - 1 - i];
         a[a.length - 1 - i] = temp;
      }
   }

}