Java 实现读取出来的文件大小变成KB,MB,TB,PB大小，或者将大单位变成KB

public static String changeFileFormat(String flow) {
        BigDecimal flows = new BigDecimal(flow);
        if (flows.compareTo(new BigDecimal(0)) > 0 && flows.compareTo(new BigDecimal(1024)) < 0) {//小于1M
            return flows.toString() + "B";
        } else if(flows.compareTo(new BigDecimal(1024)) >= 0 && flows.compareTo(new BigDecimal(1048576)) < 0){
            BigDecimal result = flows.divide(new BigDecimal(1024),2,BigDecimal.ROUND_HALF_UP);
            return  result.toString() + "KB";
        } else if(flows.compareTo(new BigDecimal(1048576)) >= 0 && flows.compareTo(new BigDecimal(1073741824)) < 0){
            BigDecimal result = flows.divide(new BigDecimal(1048576),2,BigDecimal.ROUND_HALF_UP);
            return  result.toString() + "MB";
        } else if(flows.compareTo(new BigDecimal(1073741824)) >= 0 && flows.compareTo(new BigDecimal("1099511627776")) < 0){
            BigDecimal result = flows.divide(new BigDecimal(1073741824),2,BigDecimal.ROUND_HALF_UP);
            return  result.toString() + "GB";
        } else if(flows.compareTo(new BigDecimal("1099511627776")) >= 0 && flows.compareTo(new BigDecimal("1125899906842624")) < 0){
            BigDecimal result = flows.divide(new BigDecimal("1099511627776"),2,BigDecimal.ROUND_HALF_UP);
            return  result.toString() + "TB";
        } else if(flows.compareTo(new BigDecimal("1125899906842624")) >= 0){
            BigDecimal result = flows.divide(new BigDecimal("1125899906842624"),2,BigDecimal.ROUND_HALF_UP);
            return  result.toString() + "PB";
        }else {
            return "0";
        }
    }

/**
     * 将xxZB,xxPB,xxTB,xxGB，xxMB转为 xxKB
     * @param flow xxGB，xxMB
     */
    private static String changeFileToKBInfo(String flow) {
        if(flow.contains("KB")){
            return flow.replace("KB","");
        }else if(flow.contains("MB")){
            BigDecimal flows = new BigDecimal(flow.replace("MB",""));
            BigDecimal result = flows.multiply(new BigDecimal(1024)).setScale(2,BigDecimal.ROUND_HALF_UP);
            return result.toString();
        }else if(flow.contains("GB")){
            BigDecimal flows = new BigDecimal(flow.replace("GB",""));
            BigDecimal result = flows.multiply(new BigDecimal(1048576)).setScale(2,BigDecimal.ROUND_HALF_UP);
            return result.toString();
        }else if(flow.contains("TB")){
            BigDecimal flows = new BigDecimal(flow.replace("TB",""));
            BigDecimal result = flows.multiply(new BigDecimal(1073741824)).setScale(2,BigDecimal.ROUND_HALF_UP);
            return result.toString();
        }
        else if(flow.contains("PB")){
            BigDecimal flows = new BigDecimal(flow.replace("PB",""));
            BigDecimal result = flows.multiply(new BigDecimal("1099511627776")).setScale(2,BigDecimal.ROUND_HALF_UP);
            return result.toString();
        }
        else if(flow.contains("EB")){
            BigDecimal flows = new BigDecimal(flow.replace("EB",""));
            BigDecimal result = flows.multiply(new BigDecimal("1125899906842624")).setScale(2,BigDecimal.ROUND_HALF_UP);
            return result.toString();
        }
        else {
            return "0";
        }
    }