java - 对字符串列表进行排序

Question

我被分配了这个任务:

Complete the function void sort(List l) that sorts a list l that contains the strings "one","two","three","four" (although not necessarily in that order). You should declare a Comparator, and use this with the Collections.sort function. The comparator should use the comp function described above. The list l will be altered when it is sorted.

我已经编写的代码是这样的:

import java.util.*;

public class CW3 {

    private static HashMap < String, Integer > map = new HashMap < String, Integer > ();

    public CW3() {
        map.put("one", 1);
        map.put("two", 2);
        map.put("three", 3);
        map.put("four", 4);

        List listB = Arrays.asList("A", "B", "C");
    }

    public static void main(String[] args) {
        System.out.println(new CW3().comp("one", "two"));
        System.out.println(new CW3().comp("two", "one"));
        System.out.println(new CW3().comp("one", "one"));
    }

    int comp(String s1, String s2) {
        int i1 = map.get(s1);
        int i2 = map.get(s2);
        return (i1 < i2 ? -1 : (i1 == i2 ? 0 : 1));
    }

    void sort(List l) {
        Comparator c = new Comparator() {

            public int compare(Object o1, Object o2) {
                return 0; // FIXME change this so it calls comp
            }
        };
        // now sort l using the comparator c
        // FIXME complete this line
    }

有什么想法从哪里开始吗？它说列表，所以我必须创建一个列表，但是我该如何对它们进行排序？

Answer 1

您需要做的是定义 compare方法。它应该需要两个对象 o1和o2作为参数并返回

• -1当o1 < o2
• 0当o1 == o2
• 1当o1 > o2

您的Comparator使用此方法作为决定元素顺序的基础。然后对列表进行排序 l通过调用 Collections.sort(l, c) ，其中c是Comparator你已经定义了。