blocks|key|379228|text|您可以使用Collections.max(Collection)从任何集合中查找最大元素。类似地，对于HashMap，您可以在其keySet()或values()上使用相同的方法，这取决于您想要的是最大键还是最大值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|379229|此外，如果您愿意，也可以使用TreeSet和TreeMap，它们以排序的键顺序存储元素。|379230|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#max%2528java.util.Collection%2529|1|http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html|2|http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html#keySet%2528%2529|3|http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html#values%2528%2529|4|http://docs.oracle.com/javase/7/docs/api/java/util/TreeSet.html|5|http://docs.oracle.com/javase/7/docs/api/java/util/TreeMap.html^0|5|R|1F|7|1S|8|21|8|5|R|0|1F|7|1|1S|8|2|21|8|3|0|E|7|M|7|E|7|4|M|7|5|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@$9|18|A|19|1|1A]|$9|1B|A|1C|1|1D]|$9|1E|A|1F|1|1G]|$9|1H|A|1I|1|1J]]|E|$]]|$1|F|3|G|5|6|7|1K|8|@$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]]|D|@$9|1P|A|1Q|1|1R]|$9|1S|A|1T|1|1U]]|E|$]]|$1|H|3|-4|5|6|7|1V|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]|R|$5|K|L|M|E|$N|S]]|T|$5|K|L|M|E|$N|U]]|V|$5|K|L|M|E|$N|W]]|X|$5|K|L|M|E|$N|Y]]]]

You can use <a href="http://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#max%28java.util.Collection%29"><code>Collections.max(Collection)</code></a> to find the maximum element out of any collection.
Similarly, for a <a href="http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html"><code>HashMap</code></a>, you can use the same method on its <a href="http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html#keySet%28%29"><code>keySet()</code></a> or <a href="http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html#values%28%29"><code>values()</code></a>, depending upon whether you want maximum key, or maximum value. 

Also, if you want as such, you can use a <a href="http://docs.oracle.com/javase/7/docs/api/java/util/TreeSet.html"><code>TreeSet</code></a> and <a href="http://docs.oracle.com/javase/7/docs/api/java/util/TreeMap.html"><code>TreeMap</code></a> instead, that stores the elements in sorted key order.

blocks|key|161423|text|试一试|type|unstyled|depth|inlineStyleRanges|entityRanges|data|161424|++++int+max+=+Collections.max(set);
++++int+maxKey+=+Collections.max(map.keySet());
++++int+maxValue+Collections.max(map.values());|code-block|syntax|javascript|161425|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

try

<pre><code> int max = Collections.max(set);
 int maxKey = Collections.max(map.keySet());
 int maxValue Collections.max(map.values());
</code></pre>

blocks|key|379277|text|如果您被迫使用HashSet/HashMap，那么您必须扫描整个HashSet/HashMap以找到最大值。像Collections.max()这样的库函数会这样做。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|379278|如果您想要最大值的O(1)检索，并且允许更改正在使用的集合类型，请使用排序的集合/映射(例如，TreeSet/TreeMap)。|379279|entityMap^0|7|7|F|7|W|7|14|7|1J|H|0|9|4|1B|7|1J|7|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|I|$]]

If you are forced to use a <code>HashSet</code>/<code>HashMap</code>, then you have to scan the whole <code>HashSet</code>/<code>HashMap</code> in order to find the maximum. Library functions like <code>Collections.max()</code> will do like this.

If you want <code>O(1)</code> retrieval of the maximum, and you are allowed to change the type of collection being used, use a sorted set/map (e.g. <code>TreeSet</code>/<code>TreeMap</code>).

blocks|key|161414|text|如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|161415|Set<Integer>+values+=+new+HashSet<Integer>()+{{
++++add(22);
++++add(6763);
++++add(32);
++++add(42);
++++add(33);
}};
int+maxValue+=+Integer.MIN_VALUE;
for+(int+value+:+values)+{
++++if+(value+>+maxValue)+{
++++++++maxValue+=+value;
++++}
}|code-block|syntax|javascript|161416|还有这个：|161417|Map<String,+Integer>+values+=+new+HashMap<String,+Integer>()+{{
++++put("0",+22);
++++put("1",+6763);
++++put("2",+32);
++++put("3",+42);
++++put("4",+33);
}};
int+maxValue+=+Integer.MIN_VALUE;
for+(int+value+:+values.values())+{
++++if+(value+>+maxValue)+{
++++++++maxValue+=+value;
++++}
}|161418|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Something like this:

<pre><code>Set&lt;Integer&gt; values = new HashSet&lt;Integer&gt;() {{
 add(22);
 add(6763);
 add(32);
 add(42);
 add(33);
}};
int maxValue = Integer.MIN_VALUE;
for (int value : values) {
 if (value &gt; maxValue) {
 maxValue = value;
 }
}
</code></pre>

And this: 

<pre><code>Map&lt;String, Integer&gt; values = new HashMap&lt;String, Integer&gt;() {{
 put("0", 22);
 put("1", 6763);
 put("2", 32);
 put("3", 42);
 put("4", 33);
}};
int maxValue = Integer.MIN_VALUE;
for (int value : values.values()) {
 if (value &gt; maxValue) {
 maxValue = value;
 }
}
</code></pre>

blocks|key|379359|text|在TreeMap的情况下，如果你知道键/值是随机插入的，树将或多或少是平衡的。树变得不平衡，如果按已排序的顺序插入数据，则快速查找(或插入或删除)给定元素的能力将丢失。在不平衡树的情况下，时间与n，O(n)或O(1)成正比。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|379360|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

In case of TreeMap, if you know the key/values are inserted randomly, the tree will be more or less balanced. Trees become unbalanced, if data is inserted in already sorted order, the capability to quickly find (or insert or delete) a given element is lost. In case of unbalanced tree, it will take time proportional to n, O(n) else O(1).

blocks|key|379390|text|考虑使用Apache+Commons+Math。这是API+docs。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|379391|感兴趣的类是SummaryStatistics。它与double一起工作，并动态计算最大值、最小值、平均值等(当您向其添加值时)。数据值不存储在内存中，因此此类可用于计算非常大的数据流的统计信息。|style|CODE|379392|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/math/|1|http://commons.apache.org/proper/commons-math/apidocs/index.html|2|http://commons.apache.org/proper/commons-math/apidocs/org/apache/commons/math3/stat/descriptive/SummaryStatistics.html^0|4|J|0|Q|8|1|0|Q|6|6|H|2|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]|$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@$A|11|B|12|F|G]]|9|@$A|13|B|14|1|15]]|C|$]]|$1|H|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]|P|$5|K|L|M|C|$N|Q]]|R|$5|K|L|M|C|$N|S]]]]

Consider using <a href="http://commons.apache.org/math/" rel="nofollow">Apache Commons Math</a>. Here is the <a href="http://commons.apache.org/proper/commons-math/apidocs/index.html" rel="nofollow">API docs</a>. 
The class of interest is <a href="http://commons.apache.org/proper/commons-math/apidocs/org/apache/commons/math3/stat/descriptive/SummaryStatistics.html" rel="nofollow">SummaryStatistics</a>. It works with <code>double</code>s and computes max, min, mean etc. on the fly (as you add values to it). The data values are not stored in memory, so this class can be used to compute statistics for very large data streams.

blocks|key|161536|text|下面是一个简单的方法，它可以完成您所要求的操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|161537|++public+String+getMapKeyWithHighestValue(HashMap<String,+Integer>+map)+{
++++String+keyWithHighestVal+=+"";

++++//+getting+the+maximum+value+in+the+Hashmap
++++int+maxValueInMap+=+(Collections.max(map.values()));

++++//iterate+through+the+map+to+get+the+key+that+corresponds+to+the+maximum+value+in+the+Hashmap
++++for+(Map.Entry<String,+Integer>+entry+:+map.entrySet())+{++//+Iterate+through+hashmap
++++++++if+(entry.getValue()+==+maxValueInMap)+{

++++++++++++keyWithHighestVal+=+entry.getKey();+++++//+this+is+the+key+which+has+the+max+value
++++++++}

++++}
++++return+keyWithHighestVal;
}|code-block|syntax|javascript|161538|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here is a simple method which does what you are asking:

<pre><code> public String getMapKeyWithHighestValue(HashMap&lt;String, Integer&gt; map) {
 String keyWithHighestVal = "";

 // getting the maximum value in the Hashmap
 int maxValueInMap = (Collections.max(map.values()));

 //iterate through the map to get the key that corresponds to the maximum value in the Hashmap
 for (Map.Entry&lt;String, Integer&gt; entry : map.entrySet()) { // Iterate through hashmap
 if (entry.getValue() == maxValueInMap) {

 keyWithHighestVal = entry.getKey(); // this is the key which has the max value
 }

 }
 return keyWithHighestVal;
}
</code></pre>

I would like to find the biggest number in HashSet and HashMap. Say I have the number [22,6763,32,42,33] in my HashSet and I want to find the largest number in my current HashSet..how would i do this? and Same thing for the HashMap as well. I hope you can help me with it. Thank you.

Find the Biggest number in HashSet/HashMap java

数据流

我想找出HashSet和HashMap中最大的数字。假设我的HashSet中有数字22,6763,32,42,33，我想在我当前的HashSet..how中找到最大的数字，我会这样做吗？HashMap也是如此。我希望你能帮我解决这个问题。谢谢。

问在HashSet/HashMap java中查找最大的数字
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回答 7

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