使用compareTo（）; 方法似乎不起作用

Question

I'm new to Java and am working through some problems. I'm stuck on a question that asks me to "Write a program to input ten words and then display the words that are first and last in alphabetical order". The question is ambiguous. It could mean put all the input words into alphabetical order and display the first and last of these (harder) or display the first and last inputted word in alphabetical order (easier). I wrote the following code:

import java.util.Scanner;

public class Alphabetical {

public static void main(String[] args) {

    String[] s = new String[10];
    for (int i = 0; i < 10; i++) {
        System.out.println("Enter word");
        Scanner ins = new Scanner(System.in);

        s[i] = ins.nextLine().toLowerCase();
    }

    int result = s[0].compareTo(s[10]);

    if (result < 0) {
        System.out.println(s[0]);
        System.out.println(s[10]);
    }
    else if(result>0){
        System.out.println(s[10]);
        System.out.println(s[0]);
    }
    else{
        System.out.println("Words are identical so cannot be placed in alphabetical order");
        }
    }

}

But I'm getting an out of bounds exception where the compareTo method is placed and I'm not sure why. If anybody could help that would be great. If anyone could help with the harder version of the question too, that would be even better.

Answer 1

new String[10] creates an array of 10 elements.

s[10] is the 11th element of the array since elements begin with 0. So you have to treat s[9] as your last element. compareTo is not your problem

Answer 2

Because your "s" array have 10 elements. You cahange your code

import java.util.Scanner;

public class Alphabetical {

public static void main(String[] args) {

String[] s = new String[10];
for (int i = 0; i < 10; i++) {
    System.out.println("Enter word");
    Scanner ins = new Scanner(System.in);

    s[i] = ins.nextLine().toLowerCase();
}

int result = s[0].compareTo(s[9]);

if (result < 0) {
    System.out.println(s[0]);
    System.out.println(s[9]);
}
else if(result>0){
    System.out.println(s[9]);
    System.out.println(s[0]);
}
else{
    System.out.println("Words are identical so cannot be placed in alphabetical order");
    }
}

}

Answer 3

The reason you're getting the error about the array is because arrays start with index 0 and go up to one less than the size of the array. So on an array with a size of 10, the highest index is 9. Did you try searching the exception online before posting this question?

What the question means, you'll have to clarify with the person who gave you the assignment/problem.