java根据字节数B转成合适的单位，工具类

public class beautifySizeUtil {
	public static String beautifySize(double size) {
		if (size <= 0) return "0";
		final String[] units = new String[]{"B", "KB", "MB", "GB", "TB"};
		int digitGroups = (int) (Math.log10(size) / Math.log10(1024));
		return new DecimalFormat("#,##0.#").format(size / Math.pow(1024, digitGroups)) + "" + units[digitGroups];
	}
	
	public static String beautifySize(long size) {
		if (size <= 0) return "0";
		final String[] units = new String[]{"B", "KB", "MB", "GB", "TB"};
		int digitGroups = (int) (Math.log10(size) / Math.log10(1024));
		return new DecimalFormat("#,##0.#").format(size / Math.pow(1024, digitGroups)) + "" + units[digitGroups];
	}
	
	public static void main(String[] args) {
		System.out.println(beautifySize(1));
		System.out.println(beautifySize(2048));
	    System.out.println(beautifySize(200000));
	    System.out.println(beautifySize(200000000));
	    System.out.println(beautifySize(2000000000));
	}
}

执行结果：