Java Iterator Issue - Overclock.net

LyokoHaCk · 06-19-08

Code:

public List<String> Pool;
public List<String> OtherList1;
public List<String> OtherList2;

public myClass() {
Pool = new ArrayList<String>();
OtherList1 = new ArrayList<String>();
OtherList2 = new ArrayList<String>();
} 
// Later, after adding some things to the lists...

public List<String> GPool() {
		for(Iterator<String> i = Pool.iterator(); i.hasNext();) {
			if(OtherList1.contains(i.next()) || OtherList2.contains(i.next())) { Pool.remove(i.next().toString()); }
		}
		return Pool;
	}

When trying to access GPool, I get

Code:

 java.util.ConcurrentModificationException
[20:18:10.625] java.util.AbstractList$Itr.checkForComodification(Unknown Source)
[20:18:10.625] java.util.AbstractList$Itr.next(Unknown Source)
[20:18:10.625] GPool(myClass.java:70)

Line 70 is

Code:

if(OtherList1.contains(i.next()) || OtherList2.contains(i.next())) { Pool.remove(i.next().toString()); }

I am basically trying to check if the elements of two others lists are present in "Pool" and I'd like to remove them if they are, then return the list.

rabidgnome229 · 06-19-08

Each time you call i.next() it gives you a different object. So in line 70 you're looking 2 or 3 different objects in the iterator. Most likely you are overrunning the end of the list

Code:

public List<String> GPool() {
Iterator<String> i = Pool.iterator();
if(i.hasNext())
		for(String next = i.next(); i.hasNext(); next = i.next()) {
			if(OtherList1.contains(next) || OtherList2.contains(next())) { Pool.remove(next()); }
		}
		return Pool;
	}

LyokoHaCk · 06-19-08

Quote:

Originally Posted by rabidgnome229

Each time you call i.next() it gives you a different object. So in line 70 you're looking 2 or 3 different objects in the iterator. Most likely you are overrunning the end of the list

Code:

public List<String> GPool() {
Iterator<String> i = Pool.iterator();
if(i.hasNext())
		for(String next = i.next(); i.hasNext(); next = i.next()) {
			if(OtherList1.contains(next) || OtherList2.contains(next())) { Pool.remove(next()); }
		}
		return Pool;
	}

Thanks!
So storing it in a variable and calling it that way should solve it?

rabidgnome229 · 06-19-08

stphung · 07-02-08

I would recommend using the new style for loop introduced in Java 5. Makes the code a lot more readable and you don't need to fuss with declaring an iterator, instead it is implicit.

<Begin Untested Code>

Code:

public List<String> GPool() {
    for ( String s : Pool )  {
        if ( OtherList1.contains(s) || OtherList2.contains(s) )
            Pool.remove(s);
    }
    return Pool;
}

</End Untested Code>

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Java Iterator Issue

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