java lang ClassCastException

Question

Normally  whats the reason to get java lang ClassCastException     I get the following error in my application  java lang ClassCastException   Lcom rsa authagent authapi realmstat AUTHw

User · Answer

ClassA a    lt something gt   ClassB b    ClassB  a    The 2nd line will fail if ClassA is not a subclass of ClassB  and will throw a ClassCastException

User · Answer

A ClassCastException 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  Apple myApple   new Apple    Fruit myFruit    Fruit myApple    This works because an apple  is a  fruit  However if we reverse this   Fruit myFruit   new Fruit    Apple myApple    Apple myFruit    This will throw a ClasCastException because a Fruit is not  always  an Apple   It is good practice to guard any explicit casts with an instanceof  check first   if  myApple instanceof Fruit      Fruit myFruit    Fruit myApple

User · Answer

To avoid x  instance of Long prob Add                                                    lt property name  openjpa Compatibility  value  StrictIdentityValues false   gt    in your persistence xml

User · Answer

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   Object x    this is a string   InputStream y    InputStream  x     This will throw ClassCastException   If you could provide a code sample  that would really help

User · Answer

According to the documentation   Thrown to indicate that the code has attempted to cast an Object to a subclass      of which it is not an instance  For example  the following code generates a ClassCastException        Object x   new Integer 0   System out println  String x

User · Answer

Lauren iu Dascalu s answer explains how   why you get a ClassCastException   Your exception message looks rather suspicious to me  but it might help you to know that   Lcom rsa authagent authapi realmstat AUTHw  means that the actual type of the object that you were trying to cast was com rsa authagent authapi realmstat AUTHw    i e  it was an array object   Normally  the next steps to solving a problem like this are    examining the stacktrace to figure out which line of which class threw the exception  examining the corresponding source code  to see what the expected type  and tracing back to see where the object with the  wrong  type came from

[java] java.lang.ClassCastException

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