如何统计Java中列表对象中的重复值？

Question

在Java中，我有一个这样的数组：

String[] city = {"texas", "ny", "sydney", "ny", "paris", "texas", "ny"}; 

我想排序/它们与数组...喜欢 -

texas = 2 
ny = 3 
sydney = 1 
paris = 1 

Answer 1

使用Collections.frequency()方法。

import java.util.Arrays; 
import java.util.Collections; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 

public class Test{ 
    public static void main(String[] args) { 
     String[] city = {"texas", "ny", "sydney", "ny", "paris", "texas", "ny"}; 
     List<String> asList = Arrays.asList(city); 
     Map<String, Integer> map= new HashMap<String, Integer>(); 
     for(String s: city){ 
      map.put(s,Collections.frequency(asList,s)); 
     } 
     System.out.println(map); 

    } 
}