counting number of files within a given directory (Breadth first)

Count.java

	public int count(File root){
		
		if(root == null || !root.exists()){
			System.out.println("ERROR: The source drive/directory does not exist.");
			return -1;
		}
		
		Queue<File> files = new Queue<>();
		
		files.push(root);
		int sum = 0;
		
		while(!files.empty()){
			File tmp = files.pop();
			
			if(tmp.isFile()){
				sum++;
			}else if(tmp.isDirectory()){
				for(File f : tmp.listFiles()){
					files.push(f);	
				}
			}
		}
		
		return sum;
	}