在哈希映射计数的重复值 [英] Counting duplicate values in Hashmap

问题描述

我有一个哈希表，看起来像这样：

I have a hash map that looks like this:

HashMap<String, ArrayList<String>> varX =
        new HashMap<String, ArrayList<String>>();

和我不能为我的生活工作如何算重复值的数目。
例如，如果把（001，DM）; 进入哈希映射和把（010，DM）; 还有，如果有两个值的i​​nt HashMap中的ArrayList的部分怎么算。

And I can't for the life of me work out how to count the number of duplicate values. For example, If put("001", "DM"); into the hash map and put("010", "DM"); as well, how can count if there are two values int the ArrayList section of the Hashmap.

例如，输出会是这个样子：

For example, the output would look something like this:

DM：2 因为我把两DM值到HashMap的

DM:2 as I 'put' two DM values into the Hashmap.

推荐答案

您有字符串映射到的ArrayList℃的HashMap中;弦乐＆GT; 。

做把（001，DM）此地图将不是由 @Sotirios Delimanolis指出你在评论工作的

您会得到看起来像一个错误：

You would get an error that looks like:

The method put(String, ArrayList<String>) in the type HashMap<String,ArrayList<String>> is not applicable for the arguments (String, String)

根据你的榜样行为

，你想有一个的HashMap 该地图字符串到字符串（即把（001，DM）;

Based on your example behavior, you want a HashMap that maps String to String (i.e. put("001", "DM");

现在，假设你有：

HashMap<String, String> varX = new HashMap<String, String>();

和你要计算的多少个键映射到相同的值，这里是你如何能做到这一点：

And you want to count how many keys map to the same value, here's how you can do that:

varX.put("001", "DM");
varX.put("010", "DM");

// ...

int counter = 0;
String countingFor = "DM";
for(String key : varX.keySet()) {            // iterate through all the keys in this HashMap
    if(varX.get(key).equals(countingFor)) {  // if a key maps to the string you need, increment the counter
        counter++;
    }
}
System.out.println(countingFor + ":" + counter);  // would print out "DM:2"

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