这个为什么会产生这样的错误，要怎么修改

package DateStructuresHomework;

import java.util.Scanner;

public class Comparable {
    public static Comparable getMax(Comparable []a)
    {
        int k=0;
        for (int i = 1; i 
        {
            if (a[i].compareTo(a[k])>0)
            {
                k=i;
            }
            return a[k];
        }

    }

    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        int n=in.nextInt();
        Comparable []a=new Comparable[n];
        for (int i = 0; i < n; i++)
        {
            a[i]=in.next();

        }
        System.out.println(getMax(a));
    }
}

a[i]=in.next();
a[i]是一个类对象，in.next()是输入的字符串，这没法赋值啊