Java 文件大小换算判断

    
    public String fileSizeName(String num){
        Double aDouble = Double.valueOf(num) / 1024;
        Double number;
        //保留两位小数
        DecimalFormat df = new DecimalFormat("#0.00");

        if (aDouble > 0 && aDouble < 1024){
            number = aDouble;
            return df.format(number) + "KB";
        }
        if(aDouble >= 1024 && aDouble < 1048576) {
            number = aDouble / 1024;
            return df.format(number) + "MB";
        }
        if (aDouble >= 1048576 && aDouble <= 1073741824){
            number = aDouble / 1024 / 1024;
            return df.format(number) + "GB";
        }
        return null;
    }

换算
1B（字节）=8b（位）
1 KB = 1024 B
1 MB = 1024 KB
1 GB = 1024 MB
1TB = 1024GB