Can only iterate over java lang iterable

How can I make my class iterable so I can use foreach syntax?

I changed Objects to Book in my real app, this is auto generated eclipse code seems I forgot to change objects to book before I post the question.

5 Answers 5

You need to implement the Iterable interface, which means you need to implement the iterator() method. In your case, this might look something like this:

public class BookList implements Iterable  < private final ListbList = new ArrayList(); @Override public Iterator iterator() < return bList.iterator(); >. > 

Implement the Iterable interface. That means you need to implement a method that returns an Iterator object that will iterate over the elements of a BookList .

In this case, your iterator() method could just return the result of calling bList.iterator() . (That will cause for (Book b : somBookList) to iterate over the Book objects in the BookList.bList . )

In other cases, you might need to write your own Iterator implementation class, complete with T next() , boolean hasNext() and remove() methods. For instance, if you wanted to prevent external code from removing elements from the BookList via your iterator, you might implement it like this:

public class BookList implements Iterable  < private final ListbList = new ArrayList(); //. @Override public Iterator iterator() < return new Iterator() < private final Iteratoriter = bList.iterator(); @Override public boolean hasNext() < return iter.hasNext(); >@Override public Book next() < return iter.next(); >@Override public void remove() < throw new UnsupportedOperationException("no changes allowed"); >>; > > 

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Solve the Can Only Iterate Over an Array or an Instance of Java.Lang.Iterable Error in Java

1. Can Only Iterate Over an Array or an Instance of java.lang.iterable
2. Solve the Can Only Iterate Over an Array or an Instance of java.lang.iterable Error Using Iterator()

We will learn about the Java error Can only iterate over an array or an instance of java.lang.iterable . We will see why this error occurs and the solution to it.

So without any further delay, let’s dive in.

Can Only Iterate Over an Array or an Instance of java.lang.iterable

This error is a compile time error, and it’s just as it says. It occurs when there is a problem with the iteration of an array or an instance.

While programming, the user tries to make things easier for themselves, and while doing so, the user uses loops. However, using loops is not always the correct answer.

The error can only iterate over an array or an instance of java.lang.iterable doesn’t mean that it stops the user from using a loop on an array or an instance. It means that a loop is used that doesn’t complement its conditions — for example, the for or foreach loop.

Solve the Can Only Iterate Over an Array or an Instance of java.lang.iterable Error Using Iterator()

In the case of loops, if a foreach loop is used, we have to explicitly type our iterations as sometimes foreach can cause this error to occur. We can do that by using Iterator .

Another way is to use a simple for or while loop.

Here is a simple example of explicitly iterating an array using an Iterator with a while loop. Here we will use ArrayList to demonstrate Iterator() .

An ArrayList is used here because Iterator() is a method of the ArrayList class.

A while loop is used here to make things easier. This is because while using other loops, for example, for and foreach , the Iterator() method does not work correctly.

Since Iterator() is part of a collection method, it works properly with specific loops, like the while loop.

import java.util.ArrayList; import java.util.Iterator; import java.util.List; import java.util.function.Consumer;  public class Main   public static void main(String[] args)    ListInteger> Num = new ArrayList<>(); //ArrayList is used here  Num.add(1);  Num.add(2);  Num.add(3);  Num.add(4);   IteratorInteger> value = Num.iterator(); //Here is the use of Iterator()  while (value.hasNext()) //hasNext() is used to loop. It is a method of Iterator()    System.out.println(value.next());  >  > > 

Haider specializes in technical writing. He has a solid background in computer science that allows him to create engaging, original, and compelling technical tutorials. In his free time, he enjoys adding new skills to his repertoire and watching Netflix.

Related Article — Java Error

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Error: can only iterate over an array or an instance of java.lang.Iterable

I assume Nodecollection is a com.aspose.words.NodeCollection.

If you want to use the foreach syntax you better do:

Node[] shapesArray = shapes.toArray(); for (Node node : shapesArray )< . 

Solution 2

Error: can only iterate over an array or an instance of java.lang.Iterable

It clearly says that you should iterate only on objects which are iterable.

In your code you are using

NodeCollection shapes = doc.getChildNodes(NodeType.SHAPE, true, false); . for(Shape shape: shapes) 

The for loop fails unless the shapes base class is an instance of a java.util.Collection or java.lang.Iterable .

Check if NodeCollection is a collection type class that implemented java.lang.Iterable .

the nodeCollection is from the com.aspose.words.

NodeCollection implements generic Iterable directly, without specifying the type of objects it would be handling. Hence you should explicitly generate the Iterator from the NodeCollection instance and on that you can iterate.

NodeCollection shapes = doc.getChildNodes(NodeType.SHAPE, true, false); Iterator shapesIterator = shapes.iterator(); . // now use the above iterator in for loop, as below for( Shape shape: shapesIterator ) 

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Rohan21

Comments

please help me with my error can't seem to make it work because of that can only iterate over an array or an instance of java.lang.Iterable. i want to create a barcode and read it and add it to the word document Update Post the nodeCollection is from the com.aspose.words.

import com.aspose.barcode.*; import com.aspose.barcoderecognition.BarCodeReadType; import com.aspose.barcoderecognition.BarCodeReader; import com.aspose.words.Document; import com.aspose.words.DocumentBuilder; import com.aspose.words.ImageType; import com.aspose.words.NodeCollection; import com.aspose.words.NodeType; import com.aspose.words.Shape; try < // Generate barcode image BarCodeBuilder builder = new BarCodeBuilder(); builder.setSymbologyType(Symbology.Code39Standard); builder.setCodeText("test-123"); String strBarCodeImageSave = "img.jpg"; builder.save(strBarCodeImageSave); // Add the image to a Word doc Document doc = new Document(); DocumentBuilder docBuilder = new DocumentBuilder(doc); docBuilder.insertImage(strBarCodeImageSave); String strWordFile = "docout.doc"; doc.save(strWordFile); // Recognition part // Extract image from the Word document NodeCollectionshapes = doc.getChildNodes(NodeType.SHAPE, true, false); int imageIndex = 0; for(Shape shape: shapes) < if (shape.hasImage()) < // If this shape is an image, extract image to file String extension = ImageTypeToExtension(shape.getImageData().getImageType()); String imageFileName = MessageFormat.format("Image.ExportImages.Out.", imageIndex, extension); String strBarCodeImageExtracted = "" + imageFileName; shape.getImageData().save(strBarCodeImageExtracted); // Recognize barcode from this image BarCodeReader reader = new BarCodeReader((BufferedImage) Toolkit.getDefaultToolkit().getImage(strBarCodeImageExtracted),BarCodeReadType.Code39Standard); while (reader.read()) < System.out.println("codetext: " + reader.getCodeText()); >imageIndex++; > > > catch(Exception ex) < System.out.println(ex.getMessage()); >> private static String ImageTypeToExtension(int imageType) throws Exception < switch (imageType) < case ImageType.BMP: return "bmp"; case ImageType.EMF: return "emf"; case ImageType.JPEG: return "jpeg"; case ImageType.PICT: return "pict"; case ImageType.PNG: return "png"; case ImageType.WMF: return "wmf"; default: throw new Exception("Unknown image type."); >>> 

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Error: can only iterate over an array or an instance of java.lang.Iterable

I assume Nodecollection is a com.aspose.words.NodeCollection.

If you want to use the foreach syntax you better do:

Node[] shapesArray = shapes.toArray(); for (Node node : shapesArray )< . 

Solution 2

Error: can only iterate over an array or an instance of java.lang.Iterable

It clearly says that you should iterate only on objects which are iterable.

In your code you are using

NodeCollection shapes = doc.getChildNodes(NodeType.SHAPE, true, false); . for(Shape shape: shapes) 

The for loop fails unless the shapes base class is an instance of a java.util.Collection or java.lang.Iterable .

Check if NodeCollection is a collection type class that implemented java.lang.Iterable .

the nodeCollection is from the com.aspose.words.

NodeCollection implements generic Iterable directly, without specifying the type of objects it would be handling. Hence you should explicitly generate the Iterator from the NodeCollection instance and on that you can iterate.

NodeCollection shapes = doc.getChildNodes(NodeType.SHAPE, true, false); Iterator shapesIterator = shapes.iterator(); . // now use the above iterator in for loop, as below for( Shape shape: shapesIterator ) 

Related videos on Youtube

Rohan21

Comments

please help me with my error can't seem to make it work because of that can only iterate over an array or an instance of java.lang.Iterable. i want to create a barcode and read it and add it to the word document Update Post the nodeCollection is from the com.aspose.words.

import com.aspose.barcode.*; import com.aspose.barcoderecognition.BarCodeReadType; import com.aspose.barcoderecognition.BarCodeReader; import com.aspose.words.Document; import com.aspose.words.DocumentBuilder; import com.aspose.words.ImageType; import com.aspose.words.NodeCollection; import com.aspose.words.NodeType; import com.aspose.words.Shape; try < // Generate barcode image BarCodeBuilder builder = new BarCodeBuilder(); builder.setSymbologyType(Symbology.Code39Standard); builder.setCodeText("test-123"); String strBarCodeImageSave = "img.jpg"; builder.save(strBarCodeImageSave); // Add the image to a Word doc Document doc = new Document(); DocumentBuilder docBuilder = new DocumentBuilder(doc); docBuilder.insertImage(strBarCodeImageSave); String strWordFile = "docout.doc"; doc.save(strWordFile); // Recognition part // Extract image from the Word document NodeCollectionshapes = doc.getChildNodes(NodeType.SHAPE, true, false); int imageIndex = 0; for(Shape shape: shapes) < if (shape.hasImage()) < // If this shape is an image, extract image to file String extension = ImageTypeToExtension(shape.getImageData().getImageType()); String imageFileName = MessageFormat.format("Image.ExportImages.Out.", imageIndex, extension); String strBarCodeImageExtracted = "" + imageFileName; shape.getImageData().save(strBarCodeImageExtracted); // Recognize barcode from this image BarCodeReader reader = new BarCodeReader((BufferedImage) Toolkit.getDefaultToolkit().getImage(strBarCodeImageExtracted),BarCodeReadType.Code39Standard); while (reader.read()) < System.out.println("codetext: " + reader.getCodeText()); >imageIndex++; > > > catch(Exception ex) < System.out.println(ex.getMessage()); >> private static String ImageTypeToExtension(int imageType) throws Exception < switch (imageType) < case ImageType.BMP: return "bmp"; case ImageType.EMF: return "emf"; case ImageType.JPEG: return "jpeg"; case ImageType.PICT: return "pict"; case ImageType.PNG: return "png"; case ImageType.WMF: return "wmf"; default: throw new Exception("Unknown image type."); >>> 

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[Error] Can only iterate over an array or an instance of java.lang.Iterable

posted 12 years ago

I'm trying to transverse an ArrayList with a for..each loop, but Eclipse complained:

Error:
Can only iterate over an array or an instance of java.lang.Iterable

posted 12 years ago

You are attempting to iterate over players.get(i); I don't know what that returns, but your error message indicates it is not iterable. I would have expected it to be a player, and a Player object to have a method that returns a collection of cards (getCards(), getHand(), something like that). Perhaps you need something like players.get(i).getCards().

Bartender

posted 12 years ago

• 1

If you want to traverse the players list, you just need:
If you want to iterate over the cards owned by each player, as Ralph says, it depends on what methods you're exposing in Player. Maybe:

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