for the following code,

1. why there is empty string in position 2,3,5,6,8?

2. then why "b", ":andf", "1" has no empty string behind?

    String[] splitStrs = "booo:and:fooo1o".split("o", -1);  
    System.out.println(splitStrs.length);  
    for (int i=0; i<splitStrs.length; i  ) {  
        System.out.println("\""   splitStrs[i]  "\"");  
    }

output is:

8
"b"
""
""
":and:f"
""
""
"1"
""

CodePudding user response：

why there is empty string in position 2,3,5,6,8?

When splitting on "o", there's nothing between the o's in "ooo", thus empty strings.

then why "b", ":andf", "1" has no empty string behind?

But there is an empty string at the end of your output, i.e., behind "1".

Per the documentation, a negative 2nd arg specifically means "trailing empty strings not discarded".

Always read the doc.

CodePudding user response：

The split method will find all occurances where is wanted character (in your example "o"), put a new (sub)string between current "o" and next "o", without the "o" character, in array, and continue for the whole string.

When you have, for an example "oo", it will be "" since there is nothing between those 2 "o" characters.

Let's take an example. You have a string "Oh, hello Anna! I havent seen you since 2010s!" and split this string on every place where is "a" character.

First, start from the first character, then find where is next letter "a", which is found on 14th index. Take part of the string from start to that place where is "a" and add it into an array. First element of an array will look like "Oh, hello Ann" ("A" and "a" are different characters). Then start from that "a" where I have found (14th index) and find next "a" , which is in 20th index in our example. Take part of the string from first and second "a" and copy it in an array. Then the procedure goes on until the end of the string.

Result will be:

"Oh, hello Ann"
"! I h"
"vent seen you since 2010s!"

If we split our same string on every "n", by using same logic, we will get:

"Oh, hello A"
""
"a! I have"
"t see"
" you si"
"ce 2010s"

Reason why I get an empty string on second part is because in "...Anna...", there is nothing between those 2 "n" characters

Some examples can be found on: https://www.geeksforgeeks.org/split-string-java-examples/

CodePudding user response：

Public String [ ] split ( String regex, int limit ) Parameters:

regex – a delimiting regular expression

Limit – the resulting threshold

The limit parameter can have 3 values:

• limit > 0 – If this is the case, then the pattern will be applied at most limit-1 times, the resulting array’s length will not be more than n, and the resulting array’s last entry will contain all input beyond the last matched pattern.
• limit < 0 – In this case, the pattern will be applied as many times as possible, and the resulting array can be of any size.
• limit = 0 – In this case, the pattern will be applied as many times as possible, the resulting array can be of any size, and trailing empty strings will be discarded.

please visit GeeksforGeeks site for more information regarding spliting.

"booo:and:fooo1o".split("o", -1);

why there is empty string in position 2,3,5,6,8?

Since the limit is -1 we can split it any number of times. When 'o' is used as the regex it will give all the values which are before it since there is no value it returns empty string

then why "b", ":andf", "1" has no empty string behind?

There is no empty string because there are characters after the 'o' previous match.

See this example:

class Split{
    public static void main(final String ... $){
        var out = System.out;
        final String s = "ooa";
        for(final String str : s.split("o", -1))
            out.println("\"" str "\"");

    }
}

Output:

$ javac Split.java && java Split
""
""
"a"

Why this output?

When first match happens @ index 0 which is also the very first character and it returns string before it but since there is no string it returns an empty string.

Then when second match happens with o @ index 1 it returns the string after the first match and before index 1. Since there is no characters it returns an empty string.

After that it returns a.