需要正则表达式来删除多个换行符之间的空格

Question

I am working on some rawString in which i need to remove \n from some places and Some where i need to go in next line if there showing \n.For Example Input:-

 ** As the coronavirus impact weighs, LMT to advance more\nthan $50 mln to small, medium-sized business partners in its\nsupply chain to protect jobs, support economy \n  \n  *New line should start\n\nregular \n  \n \n  \n text.

I am getting the result Partially using this code

 String str = input.replaceAll("\\n","~").replaceAll("~\\s+",System.lineSeparator()+System.lineSeparator()).replaceAll("~", " ");

Result right now i am getting:

** As the coronavirus impact weighs, LMT to advance more than $50 mln to small, medium-sized business partners in its supply chain to protect jobs, support economy


*New line should startregular 





text.

but problem is where i am getting more than one time "\n" consecutively, that all \n replace into one "\n", because at this time where i am getting "\n" with space its going to next line, e,g so it like "\n \n Keyword" in this case "Keyword" is showing in next line that correct but creating one extra line above that a problem. Can anyone please help on this.

Expected:-

** As the coronavirus impact weighs, LMT to advance more than $50 mln to small, medium-sized business partners in its supply chain to protect jobs, support economy

*New line should startregular 

text.

Input Pattern for New line

\n \n \n SomeText , \n\n SomeText\n , \n \n\n SomeText

In all above Pattern someText will start in next line.

Pattern will create space only

\nSomeText , \n\n\nSomeText\n\n , \nSomeText

in these all cases will create only space " " ,

Answer 1

I suggest the following update:

String str = input
    .replaceAll("(\\n\\s+){2,}","~") // find duplicate linefeeds with optional spaces
    .replaceAll("\\n"," ") // replace remaining linefeeds with spaces
    .replaceAll("\\s{3,}", "") // remove redundant spaces
    .replaceAll("\\s{2}", " ") // replace duplicate spaces with one
    .replaceAll("~", System.lineSeparator() + System.lineSeparator() // restore linefeeds
);

It produces the following text:

** As the coronavirus impact weighs, LMT to advance more than $50 mln to small, medium-sized business partners in its supply chain to protect jobs, support economy 

*New line should start regular 

text.

Update for new test cases

String str = input
        .replaceAll("(\\n +\\n| \\n+ )","~") // mark duplicate linefeeds with optional spaces
        .replaceAll("\\n+"," ") // replace remaining linefeeds with spaces
        .replaceAll("(~\\s*)+","~") // remove duplicate linefeed marks with optional spaces
        .replaceAll("\\s{3,}", "") // remove redundant spaces
        .replaceAll("\\s{2}", " ") // replace duplicate spaces
        .replaceAll("~", System.lineSeparator() + System.lineSeparator()) // restore linefeeds
    ;
    System.out.println("[" + str + "]");

Case 2 : "\n \n \n SomeText1, \n\n SomeText2\n,\n \n\n SomeText3"

[\n
\n
SomeText1,\n
\n
SomeText2 ,\n
\n
SomeText3]

Case 3 : "\nSomeText1, \n\n\nSomeText2\n\n, \nSomeText3"

[ SomeText1, SomeText2 , SomeText3]

Answer 2

If i didn't get it wrong you want to convert the multiple \n and spaces in one \n then

please try s = s.replaceAll("\\n\\s+\\b","\n");

for this particular use case output was

As the coronavirus impact weighs, LMT to advance more
than $50 mln to small, medium-sized business partners in its
supply chain to protect jobs, support economy 
New line should start
regular 
text.

In general

It will convert \n\n \n \n , \n \n \n , \n \n\n \n \n these kinds of patterns into a single new line ie. \n