• Here is an "answer key" to each of the coding problems
  • Swap the first and last element in the array
  • Replace all even elements with 0
  • Return true if the array is currently sorted in increasing order
  • Return true if the array contains duplicate elements

Here is an "answer key" to each of the coding problems

Swap the first and last element in the array

public class ArrayMethods
{
	private static int[] values;
	
	public ArrayMethods (int[] initialValues)
	{
		values = initialValues;
				
	}
	
	/*
	 * Swaps the first and last element in the array
	 */
	public void swapFirstAndLast ()
	{
		int size = values.length;
		int temp = values[size-1];
		values[size-1] = values[0];
		values[0] = temp;

	}

    /*
	 * Prints the arrays
	 */
	public void printArray ()
	{
		for (int i = 0 ; i < values.length ; i++)
		{
			System.out.printf("%d ", values[i]);
		}
		System.out.printf("\n");
	}

    public static void main (String[] Args)
    {
        int[] array = {1, 4, 9, 16, 25};
		
			ArrayMethods arrayMethods = new ArrayMethods(array);
						
            System.out.printf("Original array:\n");
			arrayMethods.printArray();
			arrayMethods.swapFirstAndLast();
            System.out.printf("First and last elements switched:\n");
			arrayMethods.printArray();
    }

}
ArrayMethods.main(null);

Original array:
1 4 9 16 25 
First and last elements switched:
25 4 9 16 1 

Replace all even elements with 0

public class ArrayMethods
{
	private static int[] values;
	
	public ArrayMethods (int[] initialValues)
	{
		values = initialValues;
				
	}

    /*
	 * Replaces every even element with 0
	 */
	public void replaceEvenWith0 ()
	{
		for (int i = 0 ; i < values.length ; i++)
		{
			if (i % 2 == 0)
			{
				values[i] = 0;
			}
		}
	}

	/*
	 * Prints the arrays
	 */
	public void printArray ()
	{
		for (int i = 0 ; i < values.length ; i++)
		{
			System.out.printf("%d ", values[i]);
		}
		System.out.printf("\n");
	}

    public static void main (String[] Args)
    {
		int[] array = {1, 4, 9, 16, 25};
		
		ArrayMethods arrayMethods = new ArrayMethods(array);

		System.out.printf("Original array:\n");
		arrayMethods.printArray();
		
		System.out.printf("Every even element replaced with 0:\n");
		arrayMethods.replaceEvenWith0();
		
		arrayMethods.printArray();			
	}
}
ArrayMethods.main(null);

Original array:
1 4 9 16 25 
Every even element replaced with 0:
0 4 0 16 0 

Return true if the array is currently sorted in increasing order

public class ArrayMethods
{
	private static int[] values;
	
	public ArrayMethods (int[] initialValues)
	{
		values = initialValues;
				
	}

	/*
	 * Returns true if the array is sorted in increasing order
	 */
	public boolean sortIncreasingOrder()
	{
		for (int i = 0 ; i < values.length - 1 ; i++)
		{
			if (values[i] > values[i+1] )
			{
				return false;
			}
		}
		return true;
	}

	/*
	 * Prints the arrays
	 */
	public void printArray ()
	{
		for (int i = 0 ; i < values.length ; i++)
		{
			System.out.printf("%d ", values[i]);
		}
		System.out.printf("\n");
	}

    public static void main (String[] Args)
    {
		int[] array = {1, 4, 9, 16, 25};

		ArrayMethods arrayMethods = new ArrayMethods(array);
		
		System.out.printf("Sorted Order: %b\n", arrayMethods.sortIncreasingOrder());
		arrayMethods.printArray();
	}

}
ArrayMethods.main(null);

Sorted Order: true
1 4 9 16 25 

Return true if the array contains duplicate elements

public class ArrayMethods
{
	private static int[] values;
	
	public ArrayMethods (int[] initialValues)
	{
		values = initialValues;
				
	}

    /*
	 * Returns true if the array has any duplicate elements
	 */
	public boolean duplicates ()
	{
		Arrays.sort(values);
		for (int i = 0 ; i < values.length-1 ; i++)
		{
			if (values[i] == values[i+1])
			{
				return true;
			}
		}
		return false;
	}

		/*
	 * Prints the arrays
	 */
	public void printArray ()
	{
		for (int i = 0 ; i < values.length ; i++)
		{
			System.out.printf("%d ", values[i]);
		}
		System.out.printf("\n");
	}

    public static void main (String[] Args)
    {
		int[] array = {43, 13, 8, 3, 5, 21, 1, 0, 1, 2};
			
		ArrayMethods arrayMethods = new ArrayMethods(array);
		System.out.printf("Before sort: ");
		arrayMethods.printArray();
		
		boolean duplicates = arrayMethods.duplicates();
		
		System.out.printf("After sort: ");
		arrayMethods.printArray();
		System.out.printf("Adjacent duplicate elements: %b\n", duplicates);
	}
}
ArrayMethods.main(null);

Before sort: 43 13 8 3 5 21 1 0 1 2 
After sort: 0 1 1 2 3 5 8 13 21 43 
Adjacent duplicate elements: true