Regular expression for && and &

Question

Can you please suggest me regular expression which will only match '&' from string but not '&&'.

E.g. Input String

s1 = "STRING1 && STRING2 & STRING3 AND STRING4";

I'm splitting input string with function -

String[] param = s1.split('&'); or s1.split('&(?!&&)');

Result after split should be -

param[1] = STRING1 && STRING2  
param[2] = STRING3 AND STRING4

Thank you for your replies.

Dev

Answer 1

You can make use of lookaround in regex here

(?<!&)&(?!&)

The above regex matches an & neither preceded nor followed by another &.

Answer 2

You can use this pattern as well:

[^&]&[^&]

and a call to some language specific SPLIT function should do the job.

If this is for iOS platform, try this example in a separate app:

NSString *string = @"STRING1 && STRING2 & STRING3 AND STRING4"; //[NSString stringWithFormat:@"%@", @""];

NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"[^&]&[^&]"
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];

NSUInteger numberOfMatches = [regex numberOfMatchesInString:string
                                                    options:0
                                                      range:NSMakeRange(0, [string length])];
NSLog(@"numberOfMatches : %d", numberOfMatches);
NSArray *matches = [regex matchesInString:string
                                  options:0
                                    range:NSMakeRange(0, [string length])];

for (NSTextCheckingResult *match in matches) // adjust loop per your criteria
{
    NSRange matchRange = [match range];

    // Pick the separator
    NSLog(@"::::%@", [string substringWithRange:matchRange]);

    // Splitted string array
    NSArray *arr = [string componentsSeparatedByString:[string substringWithRange:matchRange]];

    NSLog(@"Splitted String : %@", arr);
}

Answer 3

It may not be elegant but i would replace the isolated & for something else and then i would do the split.

Something like this (pseudo code, not IOS Syntax):

// s1 = "STRING1 && STRING2 & STRING3 AND STRING4";
aux=s1.replaceAll("([^&])&([^&])","$1 _SEPARATOR_ $2");
// in case of & at the beginning
aux=aux.replaceAll("^&([^&])"," _SEPARATOR_ $2");
// in case of & at the end
aux=aux.replaceAll("([^&])&$","$1 _SEPARATOR_ ");

// now aux="STRING1 && STRING2  _SEPARATOR_  STRING3 AND STRING4";
String[] params=aux.split(" _SEPARATOR_ ");