java - 如何对重复字符串进行计数和排序

Question

我有一串名字

String str = "A. Walker, L. Gordon, C. Riley, L. Gordon";

我需要计算名称出现次数并将出现次数从大到小排序。

我已经完成了计数部分，但我还需要对其进行排序。

String[] array = str.split(", ");        

List asList = Arrays.asList(array);
Set<String> mySet = new HashSet<String>(asList);
for(String s: mySet)
    System.out.println(s + " " +Collections.frequency(asList,s));

输出应该是这样的

L. Gordon 2, A. Walker 1, C. Riley 1

Answer 1

你可以这样做:

public class Test {
    static class NameFreq {
        public NameFreq(String name, int freq) {
            this.name = name;
            this.freq = freq;
        }
        String name;
        int freq;
        @Override
        public String toString() {
            return name + " " + freq;
        }
    }
    public static void main(String[] args) throws Exception {
        String str = "A. Walker, L. Gordon, C. Riley, L. Gordon";
        Map<String, NameFreq> map = new HashMap<>();
        String[] array = str.split("\\s*,\\s*");
        for(String name : array) {
            NameFreq nameFreq = map.get(name);
            if( nameFreq==null )
                map.put(name, new NameFreq(name, 1));
            else
                nameFreq.freq++;
        }

        List<NameFreq> list = new ArrayList<>(map.values());
        Collections.sort(list, new Comparator<NameFreq>() {
            @Override
            public int compare(NameFreq o1, NameFreq o2) {
                return Integer.compare(o2.freq, o1.freq);
            }
        });

        System.out.println(list);
        //output: [L. Gordon 2, A. Walker 1, C. Riley 1]
    }
}