Replace some escape characters with characters of the specified standard

demand ：

In each field A carriage return 、 A newline Use space characters (“ ”, Hexadecimal 0x20) Transference . English comma “,” Double quotes “"” Single quotation marks “’” And the vertical bar separator “|” according to RFC1738 Standards are used separately %2C、%22、%27、%7C Transference .

package com.rk.spark

import org.apache.commons.lang.StringEscapeUtils

/**
  * @program: bd1809
  * @class_name StringTest
  * @author: rk
  * @create: 2019-03-15 12:06
  * @Description:
  *  In each field   A carriage return 、 A newline   Use space characters (“ ”, Hexadecimal 0x20) Transference .  English comma “,”  Double quotes “"”
  *  Single quotation marks “’” And the vertical bar separator “|”  according to RFC1738 Standards are used separately  %2C、%22、%27、%7C Transference .
  *
  *
  * replace The parameter is char and CharSequence, That is, it can support character replacement , String substitution is also supported 
  * （CharSequence The meaning of string sequence , To put it bluntly, it's a string ）;
  *
  * replaceAll The parameter is regex, That is, replacement based on regular expression , such as ： Can pass replaceAll("\\d", "*")
  *  Change all numeric characters of a string to asterisks ;
  *
  *  The same thing ： It's all replacement , That is, to replace a character or string in the source string with a specified character or string ;
  *
  *  Difference ：replaceAll regular expression , So the parameters are parsed （ Both parameters are ）, Such as replaceAll("\\d", "*"),
  *  and replace Will not be ,replace("\\d","*") Just replace "\\d" String , It doesn't resolve to regular .
  *
  *  There's another difference ：“\” stay java Is an escape character , So we need two for one .
  *  for example System.out.println( "\\" ) ; Print only one "\". however “\” It's also the escape character in regular expressions , You need two for one .
  *  therefore ：\\\\ By java convert to \\,\\ It's also converted into \, So with replaceAll Replace “\” by "\\",
  *  To use replaceAll("\\\\","\\\\\\\\"), and replace be replace("\\","\\\\").
  *
  **/
object StringTest {
  def main(args: Array[String]): Unit = {

    val str = "aa\raabbb\rccc\nsc"
    println(str)
    // Use StringEscapeUtils.escapeJava() You can display non escape strings 
    val out: String = StringEscapeUtils.escapeJava(str)

    println(out)
    println(out.replace("\\r", " "))
    //replaceAll At the bottom is the regular expression used 
    println(out.replaceAll("\\\\r"," "))

    println(getSpecialCharTransferField(str))


  }


  def getSpecialCharTransferField(field:String):String= {
    var aa = field
    var lastStr = ""
    var lastStr01 = ""
    var lastStr02 = ""
    var lastStr03 = ""
    var lastStr04 = ""
    if(field.contains("\r")||field.contains("\n")){
      val reg = "\r|\n".r
      lastStr = field.replaceAll(reg.toString()," ")
      aa = lastStr
    }
    if(aa.contains(",")||aa.contains("\"")||aa.contains("'")||aa.contains("|")){
      lastStr01 = aa.replace(",","%2C")
      lastStr02 = lastStr01.replace("\"","%22")
      lastStr03 = lastStr02.replace("'","%27")
      lastStr04 = lastStr03.replace("|","%7C")
      aa = lastStr04
    }
    aa
  }

}

public String replaceAll(String regex, String replacement) {
    return Pattern.compile(regex).matcher(this).replaceAll(replacement);

For the above String Class replaceAll Source code , It can be seen that the bottom layer adopts regular expression .

By the way replace and replaceAll The difference between ：

    replace The parameter is char and CharSequence, That is, it can support character replacement , String substitution is also supported （CharSequence The meaning of string sequence , To put it bluntly, it's a string ）;

     replaceAll The parameter is regex, That is, replacement based on regular expression , such as ： Can pass replaceAll("\\d", "*") Change all numeric characters of a string to asterisks ;

    The same thing ： It's all replacement , That is, to replace a character or string in the source string with a specified character or string ;

    Difference ：replaceAll regular expression , So the parameters are parsed （ Both parameters are ）, Such as replaceAll("\\d", "*"), and replace Will not be ,replace("\\d","*") Just replace "\\d" String , It doesn't resolve to regular .

    There's another difference ：“\” stay java Is an escape character , So we need two for one . for example System.out.println( "\\" ) ; Print only one "\". however “\” It's also the escape character in regular expressions , You need two for one . therefore ：\\\\ By java convert to \\,\\ It's also converted into \, So with replaceAll Replace “\” by "\\", To use replaceAll("\\\\","\\\\\\\\"), and replace be replace("\\","\\\\").

    If you want to replace only the first time , have access to replaceFirst(), This method is also based on the replacement of regular expressions , But with replaceAll() The difference is , Replace only the first occurrence of the string .