在java中按sting长度对ArrayList进行排序

Question

I have an ArrayList

ArrayList<String[]> matches = new ArrayList<String[]>();

Collections.sort(matches, new Comparator<String>() {
    @Override
    public int compare(String word1, String word2) {
        return word2.length() - word1.length();
        }
    });

I want to sort this ArrayList by the length of the strings in the ArrayList. I want the list to be in descending order.

Input = ace, a, apple, cord

Output = apple, cord, ace, a

Answer 1

这适用于 Java 8。

Collections.sort(dictionary, (a, b)->Integer.compare(a.length(), b.length()));

Answer 2

you need to implement a comparator, like that:

class stringLengthComparator implements Comparator<String> {
    public int compare(String o1, String o2) {
        if (o1.length() > o2.length()) {
            return 1;
        } else if (o1.length() < o2.length()) {
            return -1;
        } else {
            return 0;
        }
    }
}

and then you just sort your ArrayList like that:

Collections.sort(matches, new stringLengthComparator());

Answer 3

1. You probably meant List<String> , not List<String[]> as the input.

2. In order to sort your list you need to use java.util.Collections.sort method with custom comparator that compares elements by length:

    List<String> list = Arrays.asList( "ace", "a", "apple", "cord" ); Collections.sort(list, new Comparator<String>() { @Override public int compare(String o1, String o2) { return o2.length() - o1.length(); } }); System.out.println(list);

Answer 4

This is exactly, how you are going to do your program using ArrayList. Make sure you import the proper java.util classes.

    public static void main(String args[])
{
    String matches[] = {"ace", "a", "apple", "cord"};
    List<String> list = new ArrayList<String>();
    Collections.addAll(list, matches);
    Collections.sort(list, new Comparator<String>(){
        public int compare(String o1, String o2)
        {
            return o1.length() - o2.length();
        }
    });

    Collections.reverse(list);
    System.out.println(list);
}

Input: "ace", "a", "apple", "cord"
Output: [apple, cord, ace, a]

PS This has been tested and it works exactly the way you want.

Answer 5

Since Java 8 you can directly use the method List.sort() :

List<String> stringList = Arrays.asList("ace", "a", "apple", "cord");
stringList.sort(Comparator.comparingInt(String::length).reversed());

stringList will be ordered in descending order:

apple, cord, ace, a