Practice writing methods that traverse and manipulate arrays. For each problem, write the complete method body.

countEvens — Return the number of even values in the array.

public static int countEvens(int[] arr)

countInRange — Return how many elements fall between lo and hi, inclusive.

public static int countInRange(int[] arr, int lo, int hi)

sumArray — Return the sum of all elements.

public static int sumArray(int[] arr)

averageArray — Return the average of all elements as a double.

public static double averageArray(int[] arr)

findLast — Return the index of the last occurrence of target, or -1 if not found.

public static int findLast(int[] arr, int target)

isSorted — Return true if the array is in non-decreasing order.

public static boolean isSorted(int[] arr)

allPositive — Return true if every element is greater than zero.

public static boolean allPositive(int[] arr)

anyNegative — Return true if at least one element is less than zero.

public static boolean anyNegative(int[] arr)

findRange — Return the difference between the largest and smallest elements.

public static int findRange(int[] arr)

longestRun — Return the length of the longest streak of consecutive equal elements.

public static int longestRun(int[] arr)

countPairs — Return the number of adjacent pairs where both elements are equal.

public static int countPairs(int[] arr)

isUnique — Return true if no two elements in the array are equal.

public static boolean isUnique(int[] arr)

reverseArray — Return a new array with the elements in reverse order.

public static int[] reverseArray(int[] arr)

runningSum — Return a new array where element i is the sum of elements 0 through i.

public static int[] runningSum(int[] arr)

removeAll — Return a new array with all occurrences of target removed.

public static int[] removeAll(int[] arr, int target)

rotateLeft — Return a new array with every element shifted one position left; the first element wraps to the end.

public static int[] rotateLeft(int[] arr)

twoSum — Return true if two different elements in the array add up to target.

public static boolean twoSum(int[] arr, int target)

intersect — Return the count of values that appear in both arrays (count each value only once).

public static int intersect(int[] arr1, int[] arr2)

mostFrequent — Return the value that appears most often (first occurrence wins ties).

public static int mostFrequent(int[] arr)

removeDuplicates — Given a sorted array, return a new array with duplicates removed.

public static int[] removeDuplicates(int[] arr)