Why do we need to put \\\\ for inserting a single \

Question

Hi,
I wanted to replace the string h"i with h'i. The following code does that.
public class replace {
     public static void main(String a[]) {
          String hel = "h\"i";
          System.out.println(hel);
          hel = hel.replaceAll("\"","\\\\");
          System.out.println(hel);
My question is why do we need to put 4(\\\\) back slash for inserting a single \? Why not just put 2(\\) back slash? Your help is appreciated.
Sundar.

Answer 1

Hi,
Could you please explain bit more on this. Im talking about the second argument in replaceAll method.
All i want is to replace the double quote in the string h"i with h\i.
Why cant the code look like this hel = hel.replaceAll("\"","\\");
If i use this code i get the following exception.
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 1
at java.lang.String.charAt(Unknown Source)
at java.util.regex.Matcher.appendReplacement(Unknown Source)
at java.util.regex.Matcher.replaceAll(Unknown Source)
at java.lang.String.replaceAll(Unknown Source)
at hello.main(hello.java:70)