blocks|key|952903|text|这是因为您转换为错误的对象-您正在尝试转换为特定类型，而您的表达式引用的对象与该类型不兼容。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|952904|Object+x+=+"this+is+a+string";
InputStream+y+=+(InputStream)+x;+//+This+will+throw+ClassCastException|code-block|syntax|javascript|952905|如果你能提供一个代码样本，那将会很有帮助...|952906|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|$]]

It's because you're casting to the wrong thing - you're trying to convert to a particular type, and the object that your express refers to is incompatible with that type. For example:

<pre><code>Object x = "this is a string";
InputStream y = (InputStream) x; // This will throw ClassCastException
</code></pre>

If you could provide a code sample, that would really help...

blocks|key|952969|text|根据the+documentation的说法|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|952970|抛出以指示代码试图将Object强制转换为它不是其实例的子类。例如，下面的代码生成一个ClassCastException：|style|CODE|952971|Object+x+=+new+Integer(0);
System.out.println((String)x);+|code-block|syntax|javascript|952972|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/lang/ClassCastException.html^0|2|H|0|0|A|6|17|I|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|6|7|Y|8|@$A|Z|B|10|F|G]|$A|11|B|12|F|G]]|9|@]|C|$]]|$1|H|3|I|5|J|7|13|8|@]|9|@]|C|$K|L]]|$1|M|3|-4|5|6|7|14|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

According to <a href="http://docs.oracle.com/javase/7/docs/api/java/lang/ClassCastException.html" rel="noreferrer">the documentation</a>:

Thrown to indicate that the code has attempted to cast an <code>Object</code> to a subclass 
 of which it is not an instance. For example, the following code generates a <code>ClassCastException</code>: 

<pre><code>Object x = new Integer(0);
System.out.println((String)x); 
</code></pre>

blocks|key|1167257|text|ClassA+a+=+<something>;
ClassB+b+=+(ClassB)+a;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1167258|如果ClassA不是ClassB的子类，第二行将失败，并抛出ClassCastException。|unstyled|1167259|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>ClassA a = &lt;something&gt;;
ClassB b = (ClassB) a;
</code></pre>

The 2nd line will fail if ClassA is not a subclass of ClassB, and will throw a ClassCastException.

blocks|key|953120|text|当您尝试将对象的实例强制转换为不是该对象的类型时，就会发生ClassCastException。仅当强制转换的对象遵循与您试图强制转换的类型的"is+a“关系时，强制转换才有效。例如|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|953121|Apple+myApple+=+new+Apple();
Fruit+myFruit+=+(Fruit)myApple;|code-block|syntax|javascript|953122|这是因为苹果“是”一种水果。然而，如果我们颠倒这一点。|953123|Fruit+myFruit+=+new+Fruit();
Apple+myApple+=+(Apple)myFruit;|953124|这将抛出一个ClasCastException，因为水果并不总是苹果。|953125|最好先用instanceof检查保护任何显式类型转换：|953126|if+(myApple+instanceof+Fruit)+{
++Fruit+myFruit+=+(Fruit)myApple;
}|953127|entityMap^0|T|I|0|0|0|0|0|4|A|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|12|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|S|3|T|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|U|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|V|$]]

A <code>ClassCastException</code> ocurrs when you try to cast an instance of an Object to a type that it is not. Casting only works when the casted object follows an "is a" relationship to the type you are trying to cast to. For Example

<pre><code>Apple myApple = new Apple();
Fruit myFruit = (Fruit)myApple;
</code></pre>

This works because an apple 'is a' fruit. However if we reverse this.

<pre><code>Fruit myFruit = new Fruit();
Apple myApple = (Apple)myFruit;
</code></pre>

This will throw a ClasCastException because a Fruit is not (always) an Apple.

It is good practice to guard any explicit casts with an <code>instanceof</code> check first:

<pre><code>if (myApple instanceof Fruit) {
 Fruit myFruit = (Fruit)myApple;
}
</code></pre>

blocks|key|1167383|text|要避免x+!instance+of+Long探测，请添加|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1167384|<property+name="openjpa.Compatibility"+value="StrictIdentityValues=false"/>|code-block|syntax|javascript|1167385|在你的persistence.xml中|1167386|entityMap^0|3|J|0|0|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]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

To avoid <code>x !instance of Long</code> prob
Add 

<pre><code>&lt;property name="openjpa.Compatibility" value="StrictIdentityValues=false"/&gt;
</code></pre>

in your persistence.xml

Normally whats the reason to get java.lang.ClassCastException ..? I get the following error in my application

<pre><code>java.lang.ClassCastException: [Lcom.rsa.authagent.authapi.realmstat.AUTHw
</code></pre>

java.lang.ClassCastException

通常情况下，获取java.lang.ClassCastException的原因是什么？我在我的应用程序中得到以下错误java.lang.ClassCastException: [Lcom.rsa.authagent.authapi.realmstat.AUTHw

问java.lang.ClassCastException
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