java常用方法集合

1.获取当前日期

// 获取当前日期
    public Date getDate(int num) {
        Calendar cal = new GregorianCalendar();
        cal.setTime(new Date());
        cal.add(Calendar.DAY_OF_MONTH, num);
        return cal.getTime();
    }

2.转换特殊字符，将json串转换为JS能直接识别的json

/**
     * 转换特殊字符，将json串转换为JS能直接识别的json
     *
     * @param oldJson
     * @return
     * @see [相关类/方法](可选)
     * @since [产品 /模块版本](可选)
     */
    public static String getJsonForJS(String oldJson) {
        String newJson = oldJson;
        newJson = newJson.replaceAll("\\\\", "\\\\\\\\");
        newJson = newJson.replaceAll("\\'", "\\\\'");
        newJson = newJson.replaceAll("\\\"", "\\\\\"");
        return newJson;
    }

 3.根据图片url获取图片的base64编码

public static String getBase64ByUrl(String urlPath){
        ByteArrayOutputStream data = new ByteArrayOutputStream();
        try {
            URL url = new URL(urlPath);
            byte[] by = new byte[1024];
            URLConnection urlConnection = url.openConnection();
            HttpURLConnection httpURLConnection = (HttpURLConnection) urlConnection;
            httpURLConnection.setConnectTimeout(1000*5);
            httpURLConnection.connect();
            InputStream inputStream = httpURLConnection.getInputStream();
            int len = -1;
            while ( (len = inputStream.read(by)) !=-1){
                data.write(by,0,len);
            }
            inputStream.close();
        } catch (Exception e) {
            logger.error("获取图片base64出错：" + e + "图片url为：" + urlPath);
        }
        return Base64.getMimeEncoder().encodeToString(data.toByteArray());
    }