java - Hitting ClassCastException to String -

edit : solved using this solution

i have strange problem. i'm trying deserialize hashmap 2 classes have since been changed, though not large degree. can't post code because it's under copyright.

notably constructor of class 2 has added field (string name) since file i'm trying deserialize serialized.

it seems class 1 trying cast string name field of class 2.

i've been using objectinputstream , objectoutputstream. part has me mystified class 1 has never had member variable of type class 2, , hashmap types have been in order . don't know what's going on, tried solution posted in this question had same exception i'm getting, despite lots of research on classloaders, still don't understand , didn't know classloader use "free variable".

here stack trace (class names changed) of problem i'm encountering:

java.lang.classcastexception: cannot assign instance of [class 1] field [class 2].name of type java.lang.string in instance of [class 2] @ java.io.objectstreamclass$fieldreflector.setobjfieldvalues(objectstreamclass.java:2034) @ java.io.objectstreamclass.setobjfieldvalues(objectstreamclass.java:1207) @ java.io.objectinputstream.defaultreadfields(objectinputstream.java:1975) @ java.io.objectinputstream.readserialdata(objectinputstream.java:1893) @ java.io.objectinputstream.readordinaryobject(objectinputstream.java:1775) @ java.io.objectinputstream.readobject0(objectinputstream.java:1327) @ java.io.objectinputstream.readobject(objectinputstream.java:349) @ java.util.hashmap.readobject(hashmap.java:1030) @ sun.reflect.generatedmethodaccessor27.invoke(unknown source) @ sun.reflect.delegatingmethodaccessorimpl.invoke(delegatingmethodaccessorimpl.java:25) @ java.lang.reflect.method.invoke(method.java:597) @ java.io.objectstreamclass.invokereadobject(objectstreamclass.java:969) @ java.io.objectinputstream.readserialdata(objectinputstream.java:1871) @ java.io.objectinputstream.readordinaryobject(objectinputstream.java:1775) @ java.io.objectinputstream.readobject0(objectinputstream.java:1327) @ java.io.objectinputstream.readobject(objectinputstream.java:349) 

code snip:

    final classloader loader = this.getclass().getclassloader();    //attempt solve classcastexception issue below.             fileinputstream fin = new fileinputstream(targetfile);             inputstream buffer = new bufferedinputstream(fin);             objectinputstream ois = new objectinputstream(buffer)   {                  /*                  * seen here: https://stackoverflow.com/questions/2358886/how-can-i-deserialize-the-object-if-it-was-moved-to-another-package-or-renamed                  */                 @override                 protected objectstreamclass readclassdescriptor() throws ioexception, classnotfoundexception    {                     objectstreamclass resultclassdescriptor = super.readclassdescriptor();                      if (resultclassdescriptor.getname().equals("class 1 [old path]"))                         resultclassdescriptor = objectstreamclass.lookup(class 1 [new path].class);                                         else if (resultclassdescriptor.getname().equals("class 2 [old path]"))                         resultclassdescriptor = objectstreamclass.lookup(class 2 [new path].class);                      return resultclassdescriptor;                 }                  /*                  * seen here : https://stackoverflow.com/questions/9110677/readresolve-not-working-an-instance-of-guavas-serializedform-appears                  */                 @suppresswarnings("rawtypes")                 @override                 protected class resolveclass(objectstreamclass objectstreamclass)                         throws ioexception, classnotfoundexception {                     return class.forname(objectstreamclass.getname(), true, loader);                 }             };              object ob = ois.readobject(); //exception happens here             hashmap<class 1, class 2> loadedmap = (hashmap<class 1, class 2>)ob;              ois.close();             buffer.close();             fin.close(); 

it looks assigning 2 incompatible classes.

class_1 = new class_2() 

class_1 has either of class_2 or superclass of class_2. seems

resultclassdescriptor = objectstreamclass.lookup(class 2 [new path].class); 

may culprit. //................... edit

class a{} class b extends a{} class c{} 

a obj = new b(); , not give error since super class of b. if cast obj class c, throw classcastexception

c cobj = (c) obj;