PERMISSION: READ_EXTERNAL , WRITE_EXTERNAL

Folder utils

public static String formatSize(long bytes, int place) {
		int level = 0;
		float number = bytes;
		String[] unit = { "bytes", "KB", "MB", "GB", "TB", "PB" };

		while (number >= 1024f) {
			number /= 1024f;
			level++;
		}

		String formatStr = null;
		if (place == 0) {
			formatStr = "###0";
		} else {
			formatStr = "###0.";
			for (int i = 0; i < place; i++) {
				formatStr += "#";
			}
		}

		DecimalFormat nf = new DecimalFormat(formatStr);

		String[] value = new String[2];
		value[0] = nf.format(number);
		value[1] = unit[level];

		return value[0]+" "+value[1];
	}

	public static long getFolderSize(File folderPath) {

		long totalSize = 0;

		if (folderPath == null) {
			return 0;
		}

		if (!folderPath.isDirectory()) {
			return folderPath.length();
		}
		try {
			File[] files = folderPath.listFiles();
			for (File file : files) {
				if (file.isFile()) {
					totalSize += file.length();
				} else if (file.isDirectory()) {
					totalSize += file.length();
					totalSize += getFolderSize(file);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return totalSize;
	}

	public static void clearFolder(File folderPath) {

		if (folderPath == null) {
			return;
		}

		if (!folderPath.isDirectory()) {
			return;
		}

		File[] files = folderPath.listFiles();
		for (File file : files) {
			if (file.isFile()) {
				file.delete();
			} else if (file.isDirectory()) {
				clearFolder(file);
				file.delete();
			}
		}
	}