判斷一個String數組中是否存在相同的元素，統計每一個元素在數組中出現的次數...

import java.io.File;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;

public class MapTest
{
    public static void main(String[] args)
    {
        Map<String, Integer> map = new HashMap<String, Integer>();
        String[] array = new String[] {"AA", "BB", "cc", "dd", "AA", "BB", "cc", "dd", "AA", "BB", "AA"};
        
        for (String str : array)
        {
            Integer num = map.get(str);
            num = null == num ? 1 : num + 1;
            map.put(str, num);
        }
        
        if (array.length != map.size())
        {
            System.out.println("存在相同的元素!");
        }
        
        Set set = map.entrySet();
        Iterator<Entry> it = set.iterator();
        while (it.hasNext())
        {
            Entry<String, Integer> entry = (Entry<String, Integer>)it.next();
            System.out.println("String : " + entry.getKey() + " num : " + entry.getValue());
        }
    }
    
}

測試結果：
存在相同的元素!
String : dd num : 2
String : AA num : 4
String : BB num : 3
String : cc num : 2