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POConcurrentModificationException with writeObject
 

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  1. POConcurrentModificationException with writeObject
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    <p>I have the following (simplified) code periodically run by a Thread in the class <code>A</code> (once per second):</p> <pre><code>Socket s = new Socket(IP,PORT); ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream()); synchronized(this) { oos.writeObject(this); //Exception HERE oos.flush(); } ... </code></pre> <p>The object (<code>this</code>) to send through the socket has an object of the class <code>B</code> as instance variable and <code>B</code> has a <code>LinkedList&lt;Long&gt;</code> as instance variable.</p> <p>The application throws <code>ConcurrentModificationException</code>:</p> <pre><code>E/AndroidRuntime(681): FATAL EXCEPTION: Thread-10 E/AndroidRuntime(681): java.util.ConcurrentModificationException E/AndroidRuntime(681): at java.util.LinkedList$LinkIterator.next(LinkedList.java:124) E/AndroidRuntime(681): at java.util.LinkedList.writeObject(LinkedList.java:973) E/AndroidRuntime(681): at java.lang.reflect.Method.invokeNative(Native Method) E/AndroidRuntime(681): at java.lang.reflect.Method.invoke(Method.java:507) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1219) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1575) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:1143) E/AndroidRuntime(681): at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:413) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1241) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1575) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:1143) E/AndroidRuntime(681): at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:413) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1241) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1575) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653) E/AndroidRuntime(681): at java.util.LinkedList.writeObject(LinkedList.java:973) E/AndroidRuntime(681): at java.lang.reflect.Method.invokeNative(Native Method) E/AndroidRuntime(681): at java.lang.reflect.Method.invoke(Method.java:507) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1219) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1575) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:1143) E/AndroidRuntime(681): at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:413) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1241) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1575) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689) E/AndroidRuntime(681): at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653) E/AndroidRuntime(681): at qoe.Application.connectUpdate(Application.java:194) E/AndroidRuntime(681): at qoe.Application.access$0(Application.java:183) E/AndroidRuntime(681): at qoe.Application$AutoUpdate.run(Application.java:217) </code></pre> <p>I run this app in Android with Eclipse and AVD, Windows 7 x64. Thanks in advance.</p> <p>Edit: After many tests I think that the method that could cause problem is the following:</p> <pre><code>/* Instance variables */ private LinkedList&lt;Long&gt; mylist; private long value; /* The incriminated method */ public synchronized void myBadMethod() { this.mylist.add(this.value); } </code></pre>
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    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
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      1. PTAnswer
    2. PO
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    3. PO
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      1. POConcurrentModificationException with writeObject
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

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