14: Static Method Finger Exercises

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(Get ready to move your fingers! Remember, you can use Eclipse to check that you’re doing these right!)

A. (2 points) Suppose you have a List<E>. Write a generic static method reverse that modifies the list in-place, reversing the order of all elements that the list contains. (Remember: the syntax for generic static methods: the type parameter goes before the return type, so the declaration will start with something like public static <E> void reverse(List<E> list).)

For example, after reverse the list [1, 2, 3, 4, 5] would be changed to [5, 4, 3, 2, 1].

B. (2 points) Write a generic static method groupUp that takes in an int parameter and a List<E> parameter, and returns a List<List<E>>.

In particular, the method should group up the elements of the List that are adjacent to each other and whose group size is determined by the int parameter.

Edge cases: If the int parameter is less than 1 or greater than the size of the input list, you should return null

For example:

If the input is the list [1, 2, 3, 4, 5] and the int is 1, the output would be the list of 5 lists [[1], [2], [3], [4], [5]].
If the input is the list [1, 2, 3, 4, 5] and the int is 2, the output would be the list of 4 lists [[1, 2], [2, 3], [3, 4], [4, 5]].
If the input is the list [1, 2, 3, 4, 5] and the int is 4, the output would be the list of 2 lists [[1, 2, 3, 4], [2, 3, 4, 5]}.
If the input is the list [1, 2, 3, 4, 5] and the int is 5, the output would be the list of 1 lists [[1, 2, 3, 4, 5]].