java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: HighscoreList$HighscoreEntry
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:368)
        at java.util.ArrayList.readObject(ArrayList.java:696)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:616)
        at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:991)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1865)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1770)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1346)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1963)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1887)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1770)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1346)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:368)
        at FileIO.load(Unknown Source)
        at Game.loadHighscores(Unknown Source)
        at Game.<init>(Unknown Source)
        at Main.main(Unknown Source)
Caused by: java.io.NotSerializableException: HighscoreList$HighscoreEntry
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1180)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
        at java.util.ArrayList.writeObject(ArrayList.java:673)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:616)
        at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:962)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
        at FileIO.save(Unknown Source)
        at Game.doHighscores(Unknown Source)
        at Game.play(Unknown Source)
        ... 1 more