How Can I Get A Regex That Allows Only 0000 Or Spaces

how can I get a regex that allows only 0000 or spaces, but not both examples: 0000000000000000000 --> OK; only spaces --> OK; 000000000 0000 --> Not Ok; a

Solution 1:

^(?:0+| +)$

Explanation:

^      # Start of string
(?:    # Either match (but don't capture)...
 0+    # one or more zeroes
|      # or
 [ ]+  # one or more spaces
)      # End of non-capturing group (used to contain the alternation)
$      # End of string

Solution 2:

This should work: (0+)|( +), doesn't it?