How to deal with java.util.ConcurrentModificationException with ArrayList

by toy

It is literally occurred when you needed to modify the list while you are iterating it in the same time.
I have two options for you to consider and use at your own risk.

This is the example that cause an error

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import java.util.ArrayList;

import java.util.List;



public class TestAddRemoveList

{



    public static void main( String args[] )

    {

        List< String > list = new ArrayList< String >();

        list.add("A");

        list.add("B");

        

        for( String str : list )

        {

            if( str.equals( "B" ) )

            {

                list.remove( new String("B" ) );

            }

        }

    }

}

This is the first option you could use CopyOnWriteArrayList but there are some drawbacks too. This is the modified result and it worked for me. 

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import java.util.List;

import java.util.concurrent.CopyOnWriteArrayList;



public class TestAddRemoveList

{



    public static void main( String args[] )

    {

        List< String > list = new CopyOnWriteArrayList< String >();

        list.add("A");

        list.add("B");

        

        for( String str : list )

        {

            if( str.equals( "B" ) )

            {

                list.remove( new String("B" ) );

            }

        }

    }

}

This is the other option. You could you iterator to modify the list

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import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;



public class TestAddRemoveList

{



    public static void main( String args[] )

    {

        List< String > list = new ArrayList< String >();

        list.add("A");

        list.add("B");

        list.add("C");

        

        for( Iterator< String > it = list.iterator(); it.hasNext() ; )

        {

            String str = it.next();

            if( str.equals( "B" ) )

            {

                it.remove();

            }

        }

        

        for( String str : list )

        {

            System.out.println( str );

        }

    }

}