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    <p>Create a Folder object to store the data, then build these objects as you read from the database. Once you have built all the Folder objects, do a final loop to bind each Folder to its parent class. Perhaps something like this:</p> <pre><code>class Folder { private String name; private int id; private int parentId; private List&lt;Folder&gt; children = new ArrayList&lt;Folder&gt;(); public Folder(String name, int id, int parentId) { this.name = name; this.id = id; this.parentId = parentId; } public void addChildFolder(Folder folder) { this.children.add(folder); } public List&lt;Folder&gt; getChildren() { return Collections.unmodifiableList(children); } public int getParentFolderId() { parentId; } public String getName() { return name; } public int getId() { return id; } } </code></pre> <p>Now as you read the data from the database, you create these Folder objects (with no children) and add them to the map with:</p> <pre><code>Map&lt;Integer, Folder&gt; data = new HashMap&lt;Integer, Folder&gt;(); ... loop through your result set getting folder data... Folder newFolder = new Folder(nameString, id, parentId); data.put(newFolder.getId(), newFolder); </code></pre> <p>Use Integer.valueOf(String) to convert String to int.</p> <p>Once you have the created all the Folders, you can make one final loop to connect the parent folders to the children, like this:</p> <pre><code>for(Folder folder : data.values()) { int parentId = folder.getParentFolderId(); Folder parentFolder = data.get(parentId); if(parentFolder != null) parentFolder.addChildFolder(folder); } </code></pre> <p>Finally, just grab the folder with id 0 and start building your Files on the disk, using folder.getChildren() as a convenient way to move down the tree. Check out the javadoc on the File object, you will particularly want to use the mkdirs() method.</p> <p>Hope that helps.</p>
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    1. POCreate folders from folder id and parent id in java
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    1. USEric Lindauer
    1. USEric Lindauer
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    1. COThis all works great for me (never new about objects before) except that in "data.put(newFolder.getId(), newFolder);" i get: "Type mismatch: cannot convert from element type Integer to Folder" and eclipse wants to convert 'folder' to an interger. Any idea what I did wrong?
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    2. COThe map generic type was wrong, I've edited the code for creating the Map to reflect this. It should be Map<Integer,Folder> data = new HashMap<Integer,Folder>();
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    3. COHow can I go about the last part, grapping the folder with id=0. I am also not sure where to put the code, currently it is all inside the pid loop
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