blocks|key|422364|text|如果要比较包含基元类型值(如byte)的数组的实际内容，请使用Arrays.equals()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|422365|System.out.println(Arrays.equals(aa,+bb));|code-block|syntax|javascript|422366|使用Arrays.deepEquals比较包含对象的数组。|422367|entityMap^0|V|F|0|0|2|H|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

Use <code>Arrays.equals()</code> if you want to compare the actual content of arrays that contain primitive types values (like byte).

<pre><code>System.out.println(Arrays.equals(aa, bb));
</code></pre>

Use <code>Arrays.deepEquals</code> for comparison of arrays that contain objects.

blocks|key|636891|text|因为它们不相等，即:它们是内部元素相等的不同数组。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|636892|尝试使用Arrays.equals()或Arrays.deepEquals()。|offset|length|style|CODE|636893|entityMap^0|0|4|F|K|J|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]|$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|I|$]]

Cause they're not equal, ie: they're different arrays with equal elements inside.

Try using <code>Arrays.equals()</code> or <code>Arrays.deepEquals()</code>.

blocks|key|422672|text|因为byte[]是可变的，所以只有当它是同一个对象时，它才会被视为.equals()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|422673|如果要比较内容，则必须使用Arrays.equals(a,+b)|422674|顺便说一句:这不是我设计它的方式。;)|422675|entityMap^0|X|9|0|D|J|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|R|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|K|$]]

As byte[] is mutable it is treated as only being <code>.equals()</code> if its the same object.

If you want to compare the contents you have to use <code>Arrays.equals(a, b)</code>

BTW: Its not the way I would design it. ;)

blocks|key|422459|text|你有没有看过Arrays.equals()|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|422460|编辑:如果根据您的评论，问题是使用字节数组作为HashMap键，那么请参阅this+question。|422461|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/6/docs/api/java/util/Arrays.html#equals%2528byte%255B%255D,%2520byte%255B%255D%2529|1|https://stackoverflow.com/questions/1058149/using-a-byte-array-as-hashmap-key-java^0|6|F|6|F|0|0|11|D|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@$9|Y|A|Z|1|10]]|E|$]]|$1|H|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]]]

have you looked at <a href="http://docs.oracle.com/javase/6/docs/api/java/util/Arrays.html#equals%28byte%5B%5D,%20byte%5B%5D%29" rel="nofollow noreferrer"><code>Arrays.equals()</code></a>?

Edit: if, as per your comment, the issue is using a byte array as a HashMap key then see <a href="https://stackoverflow.com/questions/1058149/using-a-byte-array-as-hashmap-key-java">this question</a>.

blocks|key|637325|text|如果您试图将数组用作通用的HashMap键，那么这是行不通的。考虑创建一个包含数组的自定义包装器对象，该对象的equals(...)和hashcode(...)方法返回java.util.Arrays方法的结果。例如..。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|637326|import+java.util.Arrays;

public+class+MyByteArray+{
+++private+byte[]+data;

+++//+...+constructors,+getters+methods,+setter+methods,+etc...


+++@Override
+++public+int+hashCode()+{
++++++return+Arrays.hashCode(data);
+++}

+++@Override
+++public+boolean+equals(Object+obj)+{
++++++if+(this+==+obj)
+++++++++return+true;
++++++if+(obj+==+null)
+++++++++return+false;
++++++if+(getClass()+!=+obj.getClass())
+++++++++return+false;
++++++MyByteArray+other+=+(MyByteArray)+obj;
++++++if+(!Arrays.equals(data,+other.data))
+++++++++return+false;
++++++return+true;
+++}


}|code-block|syntax|javascript|637327|这个包装类的对象可以很好地作为HashMap<MyByteArray,+OtherType>的键，并允许干净地使用equals(...)和hashCode(...)方法。|637328|entityMap^0|1J|B|1V|D|0|0|F|V|1L|B|1X|D|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|N|$]]

If you're trying to use the array as a generic HashMap key, that's not going to work. Consider creating a custom wrapper object that holds the array, and whose <code>equals(...)</code> and <code>hashcode(...)</code> method returns the results from the java.util.Arrays methods. For example...

<pre><code>import java.util.Arrays;

public class MyByteArray {
 private byte[] data;

 // ... constructors, getters methods, setter methods, etc...


 @Override
 public int hashCode() {
 return Arrays.hashCode(data);
 }

 @Override
 public boolean equals(Object obj) {
 if (this == obj)
 return true;
 if (obj == null)
 return false;
 if (getClass() != obj.getClass())
 return false;
 MyByteArray other = (MyByteArray) obj;
 if (!Arrays.equals(data, other.data))
 return false;
 return true;
 }


}
</code></pre>

Objects of this wrapper class will work fine as a key for your <code>HashMap&lt;MyByteArray, OtherType&gt;</code> and will allow for clean use of <code>equals(...)</code> and <code>hashCode(...)</code> methods.

blocks|key|637018|text|因为==和数组的equals()方法都不会比较内容；两者都只计算对象标识(==总是这样做，并且equals()不会被覆盖，所以使用的是Object中的版本)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|637019|要比较内容，请使用Arrays.equals()。|637020|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#equals%2528byte%255B%255D,%2520byte%255B%255D%2529^0|2|2|8|8|11|2|1B|8|1V|6|0|9|F|9|F|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@$9|13|A|14|1|15]]|E|$]]|$1|H|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

Because neither <code>==</code> nor the <code>equals()</code> method of the array compare the contents; both only evaluate object identity (<code>==</code> always does, and <code>equals()</code> is not overwritten, so the version from <code>Object</code> is being used).

For comparing the contents, use <a href="http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#equals%28byte%5B%5D,%20byte%5B%5D%29" rel="nofollow noreferrer"><code>Arrays.equals()</code></a>.

blocks|key|637133|text|它们返回false，因为您测试的是对象一致性而不是值相等性。这将返回false，因为您的数组实际上是内存中的不同对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|637134|如果想要测试值是否相等，应该使用java.util.Arrays中方便的比较函数|offset|length|637135|例如：|637136|import+java.util.Arrays;

'''''

Arrays.equals(a,b);|code-block|syntax|javascript|637137|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html^0|0|G|G|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@$D|W|E|X|1|Y]]|A|$]]|$1|F|3|G|5|6|7|Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

They are returning false because you are testing for object identity rather than value equality. This returns false because your arrays are actually different objects in memory.

If you want to test for value equality should use the handy comparison functions in <a href="http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html" rel="nofollow">java.util.Arrays</a>

e.g.

<pre><code>import java.util.Arrays;

'''''

Arrays.equals(a,b);
</code></pre>

blocks|key|422727|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|422728|boolean+blnResult+=+Arrays.equals(byteArray1,+byteArray2);|code-block|syntax|javascript|422729|我也不确定这一点，但试试这个也许能行得通。|422730|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Try for this:

<pre><code>boolean blnResult = Arrays.equals(byteArray1, byteArray2);
</code></pre>

I am also not sure about this, but try this may be it works.

blocks|key|422890|text|为什么a[]不等于b[]？因为在Byte[]或byte[]上真正调用的equals函数是Object.equals(Object+obj)。此函数仅比较对象标识，而不比较数组的内容。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|422891|entityMap^0|G|6|N|6|Z|6|18|P|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|G|$]]

why a[] doesn't equals b[]?
Because <code>equals</code> function really called on <code>Byte[]</code> or <code>byte[]</code> is <code>Object.equals(Object obj)</code>. This functions only compares object identify , don't compare the contents of the array.

blocks|key|422959|text|我寻找了一个数组包装器，它可以与芭乐TreeRangeMap的使用相媲美。该类不接受比较器。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|422960|经过一些研究，我意识到JDK的ByteBuffer有这个特性，并且它不复制原始数组，这是很好的。更重要的是，你可以比ByteBuffer::asLongBuffer更快，每次8字节(也不复制)。默认情况下，ByteBuffer::wrap(byte[])使用BigEndian，因此顺序关系与比较单个字节相同。|422961|。|422962|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

I looked for an array wrapper which makes it comparable to use with guava TreeRangeMap. The class doesn't accept comparator.

After some research I realized that ByteBuffer from JDK has this feature and it doesn't copy original array which is good.
More over you can compare faster with ByteBuffer::asLongBuffer 8 bytes at time (also doesn't copy). By default ByteBuffer::wrap(byte[]) use BigEndian so order relation is the same as comparing individual bytes.

.

blocks|key|422991|text|Java字节比较，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|422992|public+static+boolean+equals(byte[]+a,+byte[]+a2)+{
++++++++if+(a+==+a2)
++++++++++++return+true;
++++++++if+(a+==+null+%7C%7C+a2+==+null)
++++++++++++return+false;

++++++++int+length+=+a.length;
++++++++if+(a2.length+!=+length)
++++++++++++return+false;

++++++++for+(int+i+=+0;+i+<+length;+i%2B%2B)
++++++++++++if+(a[i]+!=+a2[i])
++++++++++++++++return+false;

++++++++return+true;
++++}|code-block|syntax|javascript|422993|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|$]]

Java byte compare,

<pre><code>public static boolean equals(byte[] a, byte[] a2) {
 if (a == a2)
 return true;
 if (a == null || a2 == null)
 return false;

 int length = a.length;
 if (a2.length != length)
 return false;

 for (int i = 0; i &lt; length; i++)
 if (a[i] != a2[i])
 return false;

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

blocks|key|423004|text|您也可以使用org.apache.commons.lang.ArrayUtils.isEquals()|type|unstyled|depth|inlineStyleRanges|entityRanges|data|423005|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|$]]

You can also use org.apache.commons.lang.ArrayUtils.isEquals()

blocks|key|423016|text|对于一个比较器来说，Arrays.equals是不够的，你不能检查包含数据的地图。我复制了Arrays.equals中的代码，并对其进行了修改以构建Comparator。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|423017|class+ByteArrays{
++++public+static+<T>+SortedMap<byte[],+T>+newByteArrayMap()+{
++++++++return+new+TreeMap<>(new+ByteArrayComparator());
++++}

++++public+static+SortedSet<byte[]>+newByteArraySet()+{
++++++++return+new+TreeSet<>(new+ByteArrayComparator());
++++}

++++static+class+ByteArrayComparator+implements+Comparator<byte[]>+{
++++++++@Override
++++++++public+int+compare(byte[]+a,+byte[]+b)+{
++++++++++++if+(a+==+b)+{
++++++++++++++++return+0;
++++++++++++}
++++++++++++if+(a+==+null+%7C%7C+b+==+null)+{
++++++++++++++++throw+new+NullPointerException();
++++++++++++}

++++++++++++int+length+=+a.length;
++++++++++++int+cmp;
++++++++++++if+((cmp+=+Integer.compare(length,+b.length))+!=+0)+{
++++++++++++++++return+cmp;
++++++++++++}

++++++++++++for+(int+i+=+0;+i+<+length;+i%2B%2B)+{
++++++++++++++++if+((cmp+=+Byte.compare(a[i],+b[i]))+!=+0)+{
++++++++++++++++++++return+cmp;
++++++++++++++++}
++++++++++++}

++++++++++++return+0;
++++++++}
++++}
}|code-block|syntax|javascript|423018|entityMap^0|A|D|19|D|22|A|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|L|$]]

<code>Arrays.equals</code> is not enough for a comparator, you can not check the map contain the data. I copy the code from <code>Arrays.equals</code>, modified to build a <code>Comparator</code>.

<pre><code>class ByteArrays{
 public static &lt;T&gt; SortedMap&lt;byte[], T&gt; newByteArrayMap() {
 return new TreeMap&lt;&gt;(new ByteArrayComparator());
 }

 public static SortedSet&lt;byte[]&gt; newByteArraySet() {
 return new TreeSet&lt;&gt;(new ByteArrayComparator());
 }

 static class ByteArrayComparator implements Comparator&lt;byte[]&gt; {
 @Override
 public int compare(byte[] a, byte[] b) {
 if (a == b) {
 return 0;
 }
 if (a == null || b == null) {
 throw new NullPointerException();
 }

 int length = a.length;
 int cmp;
 if ((cmp = Integer.compare(length, b.length)) != 0) {
 return cmp;
 }

 for (int i = 0; i &lt; length; i++) {
 if ((cmp = Byte.compare(a[i], b[i])) != 0) {
 return cmp;
 }
 }

 return 0;
 }
 }
}
</code></pre>

blocks|key|422836|text|有一种更快的方法可以做到：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|422837|Arrays.hashCode(arr1)+==+Arrays.hashCode(arr2)|code-block|syntax|javascript|422838|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|$]]

There's a faster way to do that:

<pre><code>Arrays.hashCode(arr1) == Arrays.hashCode(arr2)
</code></pre>

<pre><code>public class ByteArr {

 public static void main(String[] args){
 Byte[] a = {(byte)0x03, (byte)0x00, (byte)0x00, (byte)0x00};
 Byte[] b = {(byte)0x03, (byte)0x00, (byte)0x00, (byte)0x00};
 byte[] aa = {(byte)0x03, (byte)0x00, (byte)0x00, (byte)0x00};
 byte[] bb = {(byte)0x03, (byte)0x00, (byte)0x00, (byte)0x00};

 System.out.println(a);
 System.out.println(b);
 System.out.println(a == b);
 System.out.println(a.equals(b));

 System.out.println(aa);
 System.out.println(bb);
 System.out.println(aa == bb);
 System.out.println(aa.equals(bb));
 }
}
</code></pre>

I do not know why all of them print false.

When I run "java ByteArray", the answer is "false false false false".

I think the a[] equals b[] but the JVM is telling me I am wrong, why？？

how to compare the Java Byte[] array?

Java

public class ByteArr {    public static void main(String[] args){        Byte[] a = {(byte)0x03, (byte)0x00, (byte)0x00, (byte)0x00};        Byte[] b = {(byte)0x03, (byte)0x00, (byte)0x00, (byte)0x00}

问如何比较Java的Byte[]数组？
EN

回答 14

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何比较Java的Byte[]数组？EN

回答 14

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何比较Java的Byte[]数组？
EN