Regular expression to check Not Null values and empty strings

Question

What would be the regular expression to check a string value is "Not null and not empty" in java? i tried like this "/^$|\s+/", but seems not working.

The regex /^$|\s+/ equates to 'empty string OR any string containing at least one whitespace character' — spikeheap
– spikeheap, Commented Feb 28, 2014 at 16:43
Also, why the slashes? Java isn't PHP, it doesn't have regex delimiters (but it does require backslashes to be escaped)... — Tim Pietzcker
– Tim Pietzcker, Commented Feb 28, 2014 at 16:43

Sabuj Hassan · Accepted Answer · 2014-02-28 16:40:08Z

6

Considering this: your string can not contain "null" as string:

String.valueOf(input).matches("^null|$");

Otherwise check input != null and remove null| from the regex.

answered Feb 28, 2014 at 16:40

Sabuj Hassan

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Tim Pietzcker Over a year ago

Anchors are unnecessary with the .matches() method.

Tim Pietzcker · Accepted Answer · 2014-02-28 16:42:26Z

5

".*\\S+.*"

This means there is at least one non-whitespace character in the string. But you should watch out—if you call the string as an implicit parameter and it's null, you'll see a NullPointerException. Thus, it's probably better to check for null using conditionals.

edited Feb 28, 2014 at 16:42

Tim Pietzcker

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answered Feb 28, 2014 at 16:41

La-comadreja

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Comments

spikeheap · Accepted Answer · 2014-02-28 17:33:29Z

0

You cannot check for not-null using a regular expression, because that regex is run against the String.

To check the String isn't empty you can just use !myString.isEmpty()

so if(myString != null && !myString.isEmpty())

Of course, in Groovy it would just be if(myString) ;)

edited Feb 28, 2014 at 17:33

answered Feb 28, 2014 at 16:41

spikeheap

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