program to return max values of strings, dates, integers using Comparable interface

Question

public abstract class Main implements Comparable {

    public static void main(String[] args) {
        Integer[] intArray = {1,2,3,4,5,6,7,8,9,10};
        String[] stringArray = {"a", "b", "c", "d", "e", "f", "g", "h", "i", "j"};
        java.util.Date[] dateArray = {};

        for (int j = 0; j < 10 ; j++)
            dateArray[j] = new java.util.Date();

      /* Code to call max method and display the largest value of these */



    }

    public static Object max (Comparable[] a){
        Object tempObj = new Object();

        for (int i = 0; i < a.length - 1; i++){
            if ((a[i]).compareTo(a[i+1]) > 0 )
                tempObj = a[i];
            else 
                tempObj = a[i+1];
        }

        return tempObj;
    }

    public int compareTo(Object o) {

            if (/*this*/ > o)
                return 1;
            else if (/*this*/ < o)
                return -1;
            else
                return 0;
        }
}

While it may be easier to write it in a generic max(a, b) format, one of the requirements is for it to be written this way. I can't find a way to reference the value of the object that is actually calling the compareTo method.

Answer 1

Concerns:

• Why does Main implement Comparable? -- it shouldn't.
• Why is Main abstract? -- it shouldn't be.
• Why do you have your own compareTo method in your code? -- you shouldn't. It's never called anyway (nor should it be).

Instead just use the compareTo method that you know your Comparable objects have. You know that each item in the a array, no matter what type of item it is, implements Comparable, and so you can call this method directly on the item:

For example,

a[i].compareTo(a[i+1])

You know of course that the simplest solution is to just call java.util.Arrays.sort(a) on the array a and just take the 0th item.