Java StreamCorrupted Exception, using JSON -

i'm not sure why getting error @ bottom of code? appreciated. understand has use of objectoutputstream or objectinputstream? not entirely positive. in advance.

//main

import java.io.serializable;  class libraryofmoviedescriptions implements serializable {     public static void main(string[] args){             movielibrary movielibrary;     movielibrary = new movielibrary("movies.json");      movielibrary.tojsonfile("movies.json");     } } 

//movie description class

import org.json.jsonexception; import org.json.jsonobject; import org.json.jsonarray; import java.io.serializable;  public class moviedescription implements serializable {  private string title; private string rating; private string release; private string runtime; private string plot; private string filename; private string genre; private string actors;  public jsonobject tojsonobject() throws jsonexception {      jsonobject obj = new jsonobject();      obj.put("title", title);      obj.put("rated", rating);      obj.put("released", release);      obj.put("runtime", runtime);      obj.put("plot", plot);      obj.put("filename", filename);        jsonarray = new jsonarray();      string[] sarray = this.actors.split(" , ");      for(int = 0; < sarray.length; i++){          a.put(i);      }      obj.put("actors", a);       jsonarray g = new jsonarray();      string[] garray = this.genre.split(" , ");      for(int = 0; < garray.length; i++){          g.put(i);      }      obj.put("genre", g);       return obj; }  public moviedescription(jsonobject jsonobj) throws jsonexception{                    this.title = jsonobj.getstring("title");         this.rating = jsonobj.getstring("rating");      this.release = jsonobj.getstring("released");     this.plot = jsonobj.getstring("plot");     this.runtime = jsonobj.getstring("runtime");     this.filename = jsonobj.getstring("filename");      jsonarray g = jsonobj.getjsonarray("genre");     for(int = 0; < g.length(); i++){         this.genre += g.get(i) + ", ";     }      jsonarray = jsonobj.getjsonarray("actors");     for(int = 0; < a.length(); i++){         this.actors += a.get(i) + ", ";     } }  public moviedescription(){     title = " ";     rating = " ";     release = " ";     runtime = " ";     plot = " ";     filename = " ";     genre = " ";     actors = " "; }  public moviedescription(string title, string rating, string release, string runtime, string plot, string filename,                         string genre, string actors){     this.title = title;     this.rating = rating;     this.release = release;     this.runtime = runtime;     this.plot = plot;     this.filename = filename;     this.genre = genre;     this.actors = actors; }  public void settitle(string title){     this.title = title; }  public string gettitle(){     return title; }  public void setrating(string rating){     this.rating = rating; }  public string getrating(){     return rating; }  public void setrelease(string release){     this.release = release; }  public string getrelease(){     return this.release; }  public void setruntime(string runtime){     this.runtime = runtime; }  public string getruntime(){     return runtime; }  public void setplot(string plot){     this.plot = plot; }  public string getplot(){     return plot; }  public void setfilename(string filename){     this.filename = filename; }  public string getfilename(){     return filename; }  public void setgenre(string genre){     this.genre = genre; }  public string getgenre(){     return genre; }  public void setactors(string actors){     this.actors = actors; }  public string getactors(){     return actors; }  public string tostring(){     string string = ("title: " + title + "\n" + "rating: " + rating + "\n" + "released: " + release + "\n" +     "runtime: " + runtime + "\n" + "plot: " + plot + "\n" + "filename: " +    filename + "\n" + "genre: " + genre     + "\n" + "actors: " + actors + "\n");          return string;     }  } 

//movie library class

import org.json.jsonobject; import java.io.ioexception; import java.io.file; import java.util.arraylist; import java.util.list; import java.io.fileinputstream; import java.io.fileoutputstream; import org.json.jsontokener; import java.io.serializable; import java.io.objectinputstream; import java.io.objectoutputstream;  public class movielibrary implements serializable {  private list<moviedescription> movielib = new arraylist<moviedescription>();  private int arraysize;  public movielibrary(){     arraysize = 0; }  public boolean isempty(){     return arraysize == 0; }  public moviedescription get(string atitle){     int = indexof(atitle);     if(i == -1){         return null;     }     return movielib.get(i); }  public boolean add(moviedescription aclip){     movielib.add(aclip);     arraysize++;     return true; }  public boolean remove(string atitle){     int = indexof(atitle);     if(i != -1){         movielib.remove(i);         arraysize--;     }     return true; }  public string[] gettitles(){     string[] s = new string[movielib.size()];     for(int = 0; < movielib.size(); i++){         s[i] = movielib.get(i).gettitle();     }     return s; }  private int indexof(string atitle){     for(int = 0; < movielib.size(); i++)         if(((movielib.get(i)).gettitle()).equals(atitle)){             return i;         }     return -1; }  public movielibrary(string jsonfile){       objectinputstream in = null;     file infile = null;     jsonobject jsonobj = null;     string[] titles;      try{                 infile = new file(jsonfile);         in = new objectinputstream(new fileinputstream(infile));         jsonobj = new jsonobject(new jsontokener(in));         titles = jsonobject.getnames(jsonobj);         system.out.println("adding movies...");         for(int = 0; < titles.length; i++){             jsonobject temp = jsonobj.getjsonobject(titles[i]);             moviedescription movies = new moviedescription(temp);             movielib.add(movies);         }         system.out.println(this.gettitles());         in.close();              }     catch(exception e){         e.printstacktrace();         if(in != null){             try{                 in.close();             }             catch(ioexception z){                 z.printstacktrace();                 system.exit(0);;             }         }     } }  public void tojsonfile(string jsonfilename){      jsonobject jsonobj = new jsonobject();     objectoutputstream out = null;      try{         for(int = 0; < movielib.size(); i++)             jsonobj.put(movielib.get(i).gettitle(),movielib.get(i).tojsonobject());         out = new objectoutputstream(new fileoutputstream(jsonfilename));                out.writeobject(jsonobj.tostring());         out.close();     }     catch(exception e){         e.printstacktrace();         if(out != null){             try{             out.close();             }             catch(ioexception z){                 z.printstacktrace();                 system.exit(0);             }         }     }   } } 

and getting error:

java.io.streamcorruptedexception: invalid stream header: 7b202022   @ java.io.objectinputstream.readstreamheader(unknown source)   @ java.io.objectinputstream.<init>(unknown source)   @ movielibrary.<init>(movielibrary.java:79)   @ libraryofmoviedescriptions.main(libraryofmoviedescriptions.java:11)