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Retrieving data using java matcher and pattern

I am trying to get an alphanumeric number from a string statement for eg. UN345690 .I am using the below code.
Pattern pattern = Pattern.compile("\\d+");
Please tell me what code should I use to get the desired result.

I am trying to get an alphanumeric number
Since you already specified the regex \d+ I assume you want to extract the ordinary number 345690 from UN345690. An alphanumeric number would also include letters; but it is unclear which letters would be allowed in that case and how you would differentiate between a regular word and an alphanumeric "number".
Use a Matcher to search for your pattern in a string, then retrieve the first match.
Pattern pattern = Pattern.compile("\\d+");
Matcher matcher = pattern.matcher("UN345690");
if (matcher.find()) {
String number = matcher.group();
// do something with the extracted number
}

Regex: How to detect a pattern if an undesired sub pattern comes before the pattern?

I'm new to regex and I'm trying to use Java to detect a sequence of either: lowercase, uppercase, or digits, but not JUST digits separated by periods.
Restriction: No consecutive periods.
The sample String I have is: ###951.324.1###foo1.bar2.123proccess.this.subString
I currently have the following regex: ((\p{Alnum})+\.)+(\p{Alnum})+
I'm trying to have the pattern recognize foo1.bar2.123proccess.this.subString but my regex gives me 951.324.1 since it's a sub-pattern of the pattern I defined.
How would I go about detecting the subString foo1.bar2.123proccess.this.subString
I would imagine the general nature would be: The entire returned String should have at least 1 lowercase or uppercase char, but I'm hopelessly confused on how I would detect that in the String.

[a-zA-Z\d.]*[a-zA-Z][a-zA-Z\d.]*
This can be split into 3 parts:
[a-zA-Z\d.]* // optional sequence of letters/numbers/dots
[a-zA-Z] // MUST have a letter
[a-zA-Z\d.]* // optional sequence of letters/numbers/dots
Basically, "sandwiching" things that are required in optional things.
Try it here: https://regex101.com/r/VT4t2x/1

You may use
String rx = "\\d+(?:\\.\\d+)+|(\\p{Alnum}+(?:\\.\\p{Alnum}+)+)";
See the regex demo (pattern adjusted since regex101 does not support Java POSIX character class syntax)
The point is to match and skip dot-separated digit chunks, and only match and capture what you need. See Java demo:
String s = "###951.324.1###abc.123";
String rx = "\\d+(?:\\.\\d+)+|(\\p{Alnum}+(?:\\.\\p{Alnum}+)+)";
Pattern pattern = Pattern.compile(rx);
Matcher matcher = pattern.matcher(s);
while (matcher.find()){
if (matcher.group(1) != null) {
System.out.println(matcher.group(1));
}
} // => abc.123

Java Regular expressions for filename

I want to check the filenames sent to me against two patterns.
The first regular expression is ~*~, which should match names like ~263~. I put this in online regular expression testers and it matches. The code doesnt work though. Says no match
List<FTPFile> ret = new ArrayList<FTPFile>();
Pattern pattern = Pattern.compile("~*~");
Matcher matcher;
for (FTPFile file : files)
{
matcher = pattern.matcher(file.getName());
if(matcher.matches())
{
ret.add(file);
}
}
return ret;
Also the second pattern I need is ##* which should match strings like abc#ere#sss
Please tell me the proper patterns in java for this.

You need to define your pattern like,
Pattern pattern = Pattern.compile("~.*~");
~* in your regex ~*~ will repeat the first ~ zero or more times. So it won't match the number following the first ~. Because matches method tries to match the whole input string, this regex causes the match to fail. So you need to add .* inbetween to match strings like ~66~ or ~kjk~ . To match the strings which has only numbers present inbetween ~, you need to use ~\d+~

Try Regex:
\~.*\~
Instead:
~*~
Example:
Pattern pattern = Pattern.compile("\\~.*\\~");

Regular expression to find substring in text

I have a text file contains some strings I want to extract with Java regex,
Those strings are in format of:
$numbers,numbers,numbers....,numbers##
(start with $, followed by groups of numbers plus ,, and end with ##)
Here is my pattern.
Pattern pattern = Pattern.compile("$*##");
Matcher matcher = pattern.matcher(text);
if (matcher.find())
{
}
It turns out that nothing match my pattern
Can anyone tell me what's wrong with it?

You need to do:
Pattern pattern = Pattern.compile("\\$\\$\\d+(,\\d+)*##$");
Thanks to #Pshemo for his valuable inputs to reach the solution.

%etd(msg01) regular expression?

I am trying to write a regular expression for String like %etd(msg01).
String string = "My name is %etd(msg01) and %etd(msg02)";
Pattern pattern = Pattern.compile("%etd(.+)");
Matcher matcher = pattern.matcher(string);
while(matcher.find()) {
System.out.println(matcher.group());
}
It prints %etd(msg01) and %etd(msg02). However, I want it to print %etd(msg01) %etd(msg02) separately. I mean I am looking for non-greedy match.
How should the regular expression be changed to make it non greedy in this situation?

You should use this regex:
Pattern pattern = Pattern.compile("%etd\\([^)]+\\)");

Please place a question mark after .* or .+ to make it nongreedy. This should work for you...
Pattern pattern = Pattern.compile("%etd\\(.+?\\)");
Double slashes are also necessary in front of open and close parenthesis because they carry a special meaning in regular expression.
Another way of using is as below if you are sure that your names doesn't contain an open paranthesis after the first one.
Pattern pattern = Pattern.compile("%etd\\([^(]+\\)");