android 扫描文件栈溢出问题，自己写的扫描文件方法

class Scaning{
    	
    	private ArrayList<String> list;//保存扫描的文件
    	
    	public List<String> queue=null;//用一个list，做法跟队列一样
    	
    	public Scaning(String root){
    		list=new ArrayList<String>();
    		queue=(List<String>) Collections.synchronizedList(new LinkedList<String>());
    		queue.add(root);
    	}

    	public void scaning(){
    		new Thread(new Runnable() {
    			@Override
    			public void run() {
    						if(queue.size()>0){
    							new Thread(new ScanThread(queue.get(0))).start();
    						}
    				}
    		}).start();
    	}
    	
    	
    	class ScanThread implements Runnable{

    		private String root;
    		
    		private File [] files;
    		
    		ScanThread(String root){
    			this.root=root;
    		}
    		@Override
    		public void run() {
    			synchronized (queue) {
    				if(null!=root){
    					files=new File(root).listFiles();
    					if(null!=files){
    						for(File f:files){
    							if(f.isDirectory()){
    								queue.add(f.getAbsolutePath());
    							}else{
    								list.add(f.getAbsolutePath());
    								Log.e("ScanFile",f.getAbsolutePath());
    							}
    						}
    					}
    					queue.remove(root);

    					if(queue.size()>0){
    						new Thread(new ScanThread(queue.get(0))).start();
    					}else{
    						Log.e("ScanFile","scaning finish");
    					}
    				}
    			}
    			
    				
    		}
    	}
    }