java.util.Collections.frequency() 方法

package com.codingdict;

import java.util.*;

public class CollectionsDemo {
   public static void main(String args[]) {

      // create array list object       
      List arrlist = new ArrayList();

      // populate the list
      arrlist.add("A");
      arrlist.add("B");
      arrlist.add("C");
      arrlist.add("C");
      arrlist.add("C");      

      // check frequensy of 'C'
      int freq = Collections.frequency(arrlist, "C");

      System.out.println("Frequency of 'C' is: "+freq);    
   }    
}