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Regex to remove all special characters except periods

I need help with creating a regex that removes all special characters, including commas, but not periods. What I have tried to do is escape all the characters, symbols and punctuation I do not want. It is not working as intended.
replace("[-\\[\\]^/,'*:.!><~##\$%+=?|\"\\\\()]+".toRegex(), "")
I removed the period and tested that too. It did not work.
replace("[-\\[\\]^/,'*:!><~##\$%+=?|\"\\\\()]+".toRegex(), "")
For example, lets take the String "if {cat.is} in a hat, then I eat green eggs and ham!".
I want the result
if {cat.is} in a hat then I eat green eggs and ham (comma and exclamation symbol removed)
Note: I want to keep brackets, although braces are OK to omit.
Anyone have a solution for this?

You can use
"""[\p{P}\p{S}&&[^.]]+""".toRegex()
The [\p{P}\p{S}&&[^.]]+ pattern matches one or more (+) punctuation proper (\p{P}) or symbol (\p{S}) chars other than dots (&&[^.], using character class subtraction).
See a Kotlin demo:
println("a-b)h.".replace("""[\p{P}\p{S}&&[^.]]+""".toRegex(), ""))
// => abh.

android Regex issue

I had an issue with this regex:
(\{(([^\p{Space}][^\p{Punct}])+)\})
The problem is in number of chars. If I typing even number of chars it's works, when odd - not. I was trying to replace '+' with '?' or '*', but result still the same. How can I fix this?
I expect from this regex to block such strings: {%,$ #fd}. And allow this:
{F} or {F242fFSf23}.

Currently, it matches a {, then 1 or more repetitions of 2 chars, a non-space and then a non-punctuation, and then a }, hence you cannot use 1 char in between {...}.
To fix that, you need to use both the character classes inside bracket expression:
\{[^\p{Punct}\p{Space}]+\}
or
\{[^\p{P}\p{S}\s]+\}
Details
\{ - a { char
[^\p{Punct}\p{Space}]+ - 1 or more repetitons (+) of any char that does not belong to the \p{Punct} (punctuation) or \p{Space} (whitespace) class.
\} - a }.
Note that if the contents between the braces can only include ASCII letters or digits (in regex, [A-Za-z0-9]+), you may even use a mere
\{[A-Za-z0-9]+\}

Disassembling your regex... the reason why it only accepts an even number in between is the following part:
([^\p{Space}][^\p{Punct}])+
This basically means: something which isn't a space, exactly 1 character and something which isn't a ~punct, exactly 1 character and this several times... so exactly 1 + exactly another 1 are exactly 2 characters... and this several times will always be even.
So what you probably rather want is the following:
[^\p{Space}\p{Punct}]+
for the part shown above... which will result in the following for your complete regex:
\{[^\p{Space}\p{Punct}]+}
that of course can be simplified even more. I leave that up to you.

What's the difference between Android's Html.escapeHtml and TextUtils.htmlEncode ? When should I use one or the other?

Android has two different ways to escape / encode HTML characters / entities in Strings:
Html.escapeHtml(String), added in API 16 (Android 4.1). The docs say:
Returns an HTML escaped representation of the given plain text.
TextUtils.htmlEncode(String) For this one, the docs say:
Html-encode the string.
Reading the docs, they both seem to do pretty much the same thing, but, when testing them, I get some pretty mysterious (to me) output.
Eg. With the input: <p>This is a quote ". This is a euro symbol: €. <b>This is some bold text</b></p>
Html.escapeHtml gives:
<p>This is a quote ". This is a euro symbol: €. <b>This is some bold text</b></p>
Whereas TextUtils.htmlEncode gives:
<p>This is a quote ". This is a euro symbol: €. <b>This is some bold text</b></p>
So it seems that the second escapes / encodes the quote ("), but the first doesn't, although the first encodes the Euro symbol, but the second doesn't. I'm confused.
So what's the difference between these two methods ? Which characters does each escape / encode ? What's the difference between encoding and escaping here ? When should I use one or the other (or should I, gasp, use them both together ?) ?

You can compare their sources:
This is what Html.escapeHtml uses underneath:
https://github.com/android/platform_frameworks_base/blob/d59921149bb5948ffbcb9a9e832e9ac1538e05a0/core/java/android/text/Html.java#L387
This is TextUtils.htmlEncode:
https://github.com/android/platform_frameworks_base/blob/d59921149bb5948ffbcb9a9e832e9ac1538e05a0/core/java/android/text/TextUtils.java#L1361
As you can see, the latter only quotes certain characters that are reserved for markup in HTML, while the former also encodes non-ASCII characters, so they can be represented in ASCII.
Thus, if your input only contains Latin characters (which is usually unlikely nowadays), or you have set up Unicode in your HTML page properly, and can go along with TextUtils.htmlEncode. Whereas if you need to ensure that your text works even if transmitted via 7-bit channels, use Html.escapeHtml.
As for the different treating of the quote character (") -- it only needs to be escaped inside attribute values (see the spec), so if you are not putting your text there, you should be fine.
Thus, my personal choice would be Html.escapeHtml, as it seems to be more versatile.

Android Regular Expression - Replace all spaces '(' ')' '-'

I newt o regular expressions and been using tutorials, but the regular express I have works sometimes, but doesn't all the time. I am getting my numbers out of the contact list from my android phone. I am trying to get rid of all spaces, '(', ')', and '-'
For example:
1. (555) 867-5309 -> 5558675309
2. 1555-555-5555 -> 15555555555
3. 555-555-5555 -> 5555555555
This is the line I am using
String formatphone = contactPhone.replaceAll("\\s()-","");
For some numbers it only returns number and sometimes it doesn't change the format.
Is it correct? Do i need to format something because I am taking it out of the phone's contact list?

Put the desired characters in a character class:
String formatphone = contactPhone.replaceAll("[ ()-]","");
Ensure that you put the hyphen - at either end.

Try using this:
String formatphone = contactPhone.replaceAll("^.*[\\s\\(\\)-].*", "");
As a regular expression you're defining a set using []. In that set you include any character you want to be replaced. As ( and ) are special meaning characters, you have to escape them. As the - is a special character used to design ranges, it has to be the last character of your set, so if nothing is behind it, it's not a range, but just that character (you could escape it too, though).

android string equals returns false but they are equal

I've written this code:
Log.d("DE", p1.pId);
and I know p1.pId is "123" (it's String and all)
I then do:
if (p1.pId.equals("123"))
and it's always false.
Eclipse debugging tooltip is EXACTLY THE SAME.
I've noticed that via Log.d though I don't see 123 but 123 with 1 slashed somehow (like a special character). I've tried copy pasting in Notepad++ only to get ??123, when I paste in notepad I get smaller text.
Instead of 123 I get (maybe) ff fe ff fe ff fe 31 in hex.
Please check this picture: http://img821.imageshack.us/img821/8616/foox.png

Your string has Unicode byte order marks at the beginning. They need to be stripped off. If you show the code where is p1.pId coming from, perhaps we can explain how it can be fixed there.