Question

任何人都可以帮助我吗？我需要编写一个程序，我在arraylist中有10个元素，我需要找到它有多少重复值，并计算和显示值。

前：说我有

list = {"stack", "overflow", "stack", 
        "yahoo", "google", "msn", 
        "MSN", "stack", "overflow", "user" }

结果应该是：

stack = 3
overflow = 2
google = 1
msn = 2
yahoo =1
user = 1

Answer 1

使用HashMap。这是一个简单的实现

List<String> strings = new ArrayList<String>();
strings.put("stack", "overflow", "stack", "yahoo", "google", "msn", "MSN", "stack", "overflow", "user");

Map<String, Integer> counts = new HashMap<String, Integer>();

for (String str : strings) {
    if (counts.containsKey(str)) {
        counts.put(str, counts.get(str) + 1);
    } else {
        counts.put(str, 1);
    }
}

for (Map.Entry<String, Integer> entry : counts.entrySet()) {
    System.out.println(entry.getKey() + " = " + entry.getValue());
}

Answer 2

使用Google Guava图书馆的MultiSet。它支持添加多个元素，并计算多重集包含的每个元素的出现次数。

Multiset<String> wordsMultiset = HashMultiset.create();
wordsMultiset.addAll(words);
for(Multiset.Entry<String> entry : wordsMultiset.entrySet() ){
     System.out.println("Word : "+entry.getElement()+" count -> "+entry.getCount());
}

Answer 3

使用hashmap
像这样：

Map<String, Integer> occurrencies = new HashMap<String, Integer>();
for (String word : list) {
    occurrencies.put(word, occurrencies.containsKey(word)
    ? occurrencies.get(word) + 1 : 1);
}
for (Entry<String, Integer> entry : occurrencies.entrySet()) {
    System.out.println("Word: "+entry.getKey()
                     + ", occurences: "+entry.getValue());
}

Answer 4

Map<String, Integer> frequency = new HashMap<String, Integer>();
for (String element : list) {
    if (frequency.contains(element)) {
        frequency.put(element, frequency.get(element) + 1);
    }
    else {
        frequency.put(element, 1);
    }
}
for (Map.Entry<String, Integer> entry : frequency.entrySet()) {
    System.out.print(entry.getKey() + " = " + entry.getValue() + " ");
}
System.out.println();

Answer 5

使用HashMap

Map<String, Integer> freqMap = new HashMap<String, Integer>();

Answer 6

创建Map<String, Integer>，然后迭代ArrayList。

然后对每个元素： -

如果它已经存在于Map中，请将该元素的Integer值增加1
如果不存在，请添加initial Integer值为1

在arraylist中查找重复元素并显示

6 个答案: