blocks|key|816161|text|看看Javadoc+(我想它是该项目的Javadoc，而不是另一个项目，如果您能链接到它会很好)，这里定义了一个采用构造函数的Comparator<K>。使用这个构造函数，并传递给它一个Comparator<byte[]>，它给出了您想要的顺序。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|816162|entityMap|0|LINK|mutability|MUTABLE|url|http://www.mapdb.org/apidocs/org/mapdb/BTreeMap.html#BTreeMap%2528org.mapdb.Engine,%2520long,%2520int,%2520boolean,%2520long,%2520org.mapdb.BTreeKeySerializer,%2520org.mapdb.Serializer,%2520java.util.Comparator,%2520int,%2520boolean%2529^0|1R|D|2L|I|1M|4|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@$9|S|A|T|1|U]]|E|$]]|$1|F|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

Looking at the Javadoc (I guess it is the Javadoc for that project and not another one, it would have been nice of you to link to it) there is defined a <a href="http://www.mapdb.org/apidocs/org/mapdb/BTreeMap.html#BTreeMap%28org.mapdb.Engine,%20long,%20int,%20boolean,%20long,%20org.mapdb.BTreeKeySerializer,%20org.mapdb.Serializer,%20java.util.Comparator,%20int,%20boolean%29" rel="nofollow">constructor</a> that takes a <code>Comparator&lt;K&gt;</code>. Use that constructor and pass it a <code>Comparator&lt;byte[]&gt;</code> that gives the ordering you desire.

blocks|key|2424383|text|我认为您必须将字节数组包装在实现可比较的类中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2424384|import+org.apache.commons.lang.builder.CompareToBuilder;
public+class+Key+implements+Comparable<Key>+{
++++private+final+byte[]+data;

++++public+Key(final+byte[]+data)+{
++++++++this.data+=+data;
++++}

++++public+int+compareTo(final+Key+k)+{
++++++++return+new+CompareToBuilder().append(data,+k.data).toComparison();
++++}

++++/**
+++++*+{@inheritDoc}
+++++*/
++++@Override
++++public+int+hashCode()+{
++++++++final+int+prime+=+31;
++++++++int+result+=+1;
++++++++result+=+prime+*+result+%2B+getOuterType().hashCode();
++++++++result+=+prime+*+result+%2B+Arrays.hashCode(data);
++++++++return+result;
++++}

++++/**
+++++*+{@inheritDoc}
+++++*/
++++@Override
++++public+boolean+equals(final+Object+obj)+{
++++++++if+(this+==+obj)+{
++++++++++++return+true;
++++++++}
++++++++if+(obj+==+null)+{
++++++++++++return+false;
++++++++}
++++++++if+(getClass()+!=+obj.getClass())+{
++++++++++++return+false;
++++++++}
++++++++final+Key+other+=+(Key)+obj;
++++++++if+(!getOuterType().equals(other.getOuterType()))+{
++++++++++++return+false;
++++++++}
++++++++if+(!Arrays.equals(data,+other.data))+{
++++++++++++return+false;
++++++++}
++++++++return+true;
++++}

++++private+Test+getOuterType()+{
++++++++return+Test.this;
++++}

}|code-block|syntax|javascript|2424385|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|$]]

I think you must wrap the byte array in a class that implements Comparable:

<pre><code>import org.apache.commons.lang.builder.CompareToBuilder;
public class Key implements Comparable&lt;Key&gt; {
 private final byte[] data;

 public Key(final byte[] data) {
 this.data = data;
 }

 public int compareTo(final Key k) {
 return new CompareToBuilder().append(data, k.data).toComparison();
 }

 /**
 * {@inheritDoc}
 */
 @Override
 public int hashCode() {
 final int prime = 31;
 int result = 1;
 result = prime * result + getOuterType().hashCode();
 result = prime * result + Arrays.hashCode(data);
 return result;
 }

 /**
 * {@inheritDoc}
 */
 @Override
 public boolean equals(final Object obj) {
 if (this == obj) {
 return true;
 }
 if (obj == null) {
 return false;
 }
 if (getClass() != obj.getClass()) {
 return false;
 }
 final Key other = (Key) obj;
 if (!getOuterType().equals(other.getOuterType())) {
 return false;
 }
 if (!Arrays.equals(data, other.data)) {
 return false;
 }
 return true;
 }

 private Test getOuterType() {
 return Test.this;
 }

}
</code></pre>

blocks|key|243668|text|MapDB提供byte[]数组比较器:+Fun.BYTE_ARRAY_COMPARATOR|type|unstyled|depth|inlineStyleRanges|entityRanges|data|243669|下面是如何在代码中使用的示例：|243670|+++Map<byte[],+Object>+map+=+db.createTreeMap("map")
+++++++++++++++.comparator(Fun.BYTE_ARRAY_COMPARATOR)
+++++++++++++++.makeOrGet();|code-block|syntax|javascript|243671|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

MapDB provides byte[] array comparator: Fun.BYTE_ARRAY_COMPARATOR

Here is an example howto use in code:

<pre><code> Map&lt;byte[], Object&gt; map = db.createTreeMap("map")
 .comparator(Fun.BYTE_ARRAY_COMPARATOR)
 .makeOrGet();
</code></pre>

Is there any way to use byte array as a key in <code>BTreeMap</code> like this:

<pre><code>BTreeMap&lt;byte[], Integer&gt; myBTreeMap = db.getTreeMap("myBTreeMap");
</code></pre>

Currently this exception is thrown when trying to put new object into the map:

<pre><code>Exception in thread "main" java.lang.ClassCastException: [B cannot be cast to java.lang.Comparable ...
</code></pre>

What is proper way of making this to work? I would like to know solution without using wrapper classes.

Any ideas are welcome.

[UPDATE]

I've used proposed solution by SJuan76:

<pre><code> BTreeMap&lt;byte[], Integer&gt; myBTreeMap = db.createTreeMap("myBTreeMap")
 .comparator(SignedBytes.lexicographicalComparator())
 .makeOrGet();
</code></pre>

Used comparator can be found in Guava library if needed.

How to use byte array as a key in MapDB's implementation of BTreeMap

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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是否有任何方法可以在BTreeMap中使用字节数组作为键，如：BTreeMap<byte[], Integer> myBTreeMap = db.getTreeMap("myBTreeMap");当前，当试图将新对象放入映射时，将引发此异常：Exception in thread "main" java.lang.Cl...

问如何使用字节数组作为MapDB实现BTreeMap的关键
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问如何使用字节数组作为MapDB实现BTreeMap的关键EN