Question

This is my string

String s = "asadsdas357902||190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC";

I split it as

String a[] = s.split(s, i);

outputs: i=0

        |   |   1   9   0   |   |   R   U   E       R   A   C   H   E   L   L   E   |   |   S   T   |   |   |   L   E   S       C   È   D   R   E   S   |   J   7   T   1   J   9   |   Q   C   

First two indexes of array are empty nad then each index has one character.

When i=1, output is the whole original string

asadsdas357902||190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC

when i=2, output is

    ||190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC  

first index of array is empty and second contains the substring from first | symbol

when i=3, output is

        ||190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC

first two indexes are empty and last index has the same substring as for i=2

when i=4, output is

        |   |190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC   

first two indexes empty, next contains a pipe and last the rest

when i=5, output is

        |   |   190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC    

first two empty, next two pipe character and last the remaining.

as the i value increases, the output is

first two indexes empty
next all indexes except last contains one character each
last index contains the remaining string

My questions are

1. Why it is not considering the first word before the first pipe symbol?
2. Why it is making he first two indexes empty for every value of i except 1?
3. The pattern is the same string here, so what is matched here and how the outputs come?

And another thing is if I replace the pipe symbol with any other symbol such as @ or ! or %, the output is

array length is 2 with both indexes has empty strings. this is for i>=2

for i=0

the array length is also 0

for i=1

the array length is 1 containing the whole string.

Is it taking the pipe symbol as a special regex symbol?

Any help appreciable.

Answer 1

split method takes a regex as an input param. Now the regex in your case is
asadsdas357902||190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC and the second parameter i is the number of times that split operation is applied. This is the explanation of your regex

                         // Match either the regular expression below (attempting the next alternative only if this one fails)
   "asadsdas357902" +       // Match the characters “asadsdas357902” literally
"|" +                    // Or match regular expression number 2 below (attempting the next alternative only if this one fails)
   "|" +                    // Empty alternative effectively truncates the regex at this point because it will always find a zero-width match
                         // Or match regular expression number 3 below (attempting the next alternative only if this one fails)
   "190" +                  // Match the characters “190” literally
"|" +                    // Or match regular expression number 4 below (attempting the next alternative only if this one fails)
   "|" +                    // Empty alternative effectively truncates the regex at this point because it will always find a zero-width match
                         // Or match regular expression number 5 below (attempting the next alternative only if this one fails)
   "RUE\\ RACHELLE" +        // Match the characters “RUE RACHELLE” literally
"|" +                    // Or match regular expression number 6 below (attempting the next alternative only if this one fails)
   "|" +                    // Empty alternative effectively truncates the regex at this point because it will always find a zero-width match
                         // Or match regular expression number 7 below (attempting the next alternative only if this one fails)
   "ST" +                   // Match the characters “ST” literally
"|" +                    // Or match regular expression number 8 below (attempting the next alternative only if this one fails)
   "|" +                    // Empty alternative effectively truncates the regex at this point because it will always find a zero-width match
                         // Or match regular expression number 9 below (attempting the next alternative only if this one fails)
   "|" +                    // Empty alternative effectively truncates the regex at this point because it will always find a zero-width match
                         // Or match regular expression number 10 below (attempting the next alternative only if this one fails)
   "LES\\ CÈDRES" +          // Match the characters “LES CÈDRES” literally
"|" +                    // Or match regular expression number 11 below (attempting the next alternative only if this one fails)
   "J7T1J9" +               // Match the characters “J7T1J9” literally
"|" +                    // Or match regular expression number 12 below (the entire match attempt fails if this one fails to match)
   "QC"                     // Match the characters “QC” literally

So, your regex is effectively equivalent to asadsdas357902| in a way because the regex that comes after it is never tested. See the split method documentation here String#split

This code would give you the same output

private static void splitWithPipe() {
    String s = "asadsdas357902||190||RUE RACHELLE||ST|||LES CÈDRES|J7T1J9|QC";
    for (int i = 0; i < 10; i++) {
        String a[] = s.split("asadsdas357902|", i); 
        System.out.println(Arrays.toString(a));
    }
}