Develop Reference

Custom Regular Expression in Java

I have to implement a function that check if a string is compliant to a regular expression, I have wrote a method that parse a list of filename, for each file name I need to check if respect the regexp.
The filename is composed like as follow (just an example):
verbale.pdf.001.001
image.jpg.002.001
The string is always composed by:
extension (only jpg or pdf) "." a group of three number "." a group of three number
With this regexp I need to check if the string in input end as described above, I have currently implemented this:
Pattern rexExp = Pattern.compile("((\\.jpg)|(\\.pdf))\\.[0-9]{3}\\.[0-9]{3}");
But not work properly, is it a good idea implement a regExp to check if a filename end with a certain path ?

Less greedy than the other answer, think it suits you:
\\w+\\.(jpg|pdf)(\\.\\d{3}){2}
file name, only composed of letters, numbers and _
dot
jpg or pdf formats
another dot
three digits
the dot and the three digits repeated

This should work :
.*\\w{3}\\.\\d{3}\\.\\d{3}
.* = any Characters (like "verbale123")
\\w{3} = any 3 alphabetic\numeric characters
\\. = a dot
\\d{3} = any three numeric characters

To check if a string ends with pdf or jpg and two sequences of . and 3 digits, you may use
(?i)(?:jpg|pdf)(?:\.[0-9]{3}){2}$
See the regex demo
Details
(?i) - case insensitive flag
(?:jpg|pdf) - either jpg or pdf
(?:\.[0-9]{3}){2} - 2 repetitions of a . and 3 digits
$ - end of string.
Use with Matcher#find() (as matches() anchors the match at the start and end of the string, while a partial match is required when using this pattern), example demo:
String s = "verbale.pdf.001.001";
Matcher matcher = Pattern.compile("(?i)(?:jpg|pdf)(?:\\.[0-9]{3}){2}$").matcher(s);
if (matcher.find()){
System.out.println("Valid!");
}

Rules of escaping characters in Android and ios strings

I'm wondering in strings.xml and localizable.strings, what are the treatments towards single(') and double(") quote and also line breaks.
My understandings are:
1. string.xml needs all single and double quotes to be escaped. e.g. I\'m or \"story\"
2. localizable.strings only needs the double quotes to be escaped. e.g. \"story\"
3. line breaks in string.xmlwill need to be represented by \n
4. line breaks in localizable.stringscan be either \n or literal line breaks.
Are my understandings correct? Please let me know if other differences. Thank you very much!

How to remove hyphen from TextUtils.split(line, "-")?

I found a dictionary sample in GitHub that I am currently experimenting with. The sample database used hyphen between the searched word and the word's meaning. So something like this.
abbey - n. a monastery ruled by an abbot
I looked into the dictionary database java file and found the following code:
String[] strings = TextUtils.split(line, "-");
I have my own database that translates Korean words to English. However I didn't use hyphen while creating it. So is there a way to not use hyphen or any other symbols but simply spaces? Also this is part of an android app.
Edit- An example of my own dictionary would be something like
abbey a monastery ruled by an abbot
Edit-
The problem here is that the old code only differentiates and recognizes the words and the meaning only if they are separated by hyphen. How do I make this so it works with spaces alone.

To remove a character in a String use String.replace
String newString = line.replace("-","");
To replace with a space simply use
String newString = line.replace("-"," ");

String mystring = mystring 1.replace("_"," "); if you want space give space.

As I understand it, you want to split your String to get the output like
abbey - n. a monastery ruled by an abbot
[abbey][n. a monastery ruled by an abbot]
You can use String.split(String, int) to force the number of split.
The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n - 1 times
Let's use it like :
String[] array = s.split(" ", 2);
This will split your String on the regex " " but will limit the size of the output to 2 cells. So it will only split once, put the left part on the first cell and the right part on the second cell.
Without this limit argument, the method would keep split the right part again using a bigger array.
Note: this will be a problem if your word is a sentence in the left part.

What is the the double quotation marks in strings.xml used for?

Just a little while ago, I was looking around on GitHub， and I found there were some double quotation marks beside the string value in some strings.xml just like this:
<string name="ClipMmi" msgid="6952821216480289285">"来电显示"</string>
In short I mean this
"来电显示"
For full example please click here.
I don't know what is the "" used for? Because if I remove the "" beside the string value (e.g. "来电显示" change to 来电显示), the output won't change any more, both "来电显示" and 来电显示 will print 来电显示 as the output.
So does the quotations make any sense here?

It makes sense on languages that are using simple quotes '.
If simple quotes aren't escaped like this, \', Lint will detect an error.
Using double quotes at the start and at the end of a string value will allow you to omit these backslashes.
There may be other purposes I didn't discovered yet.

New Line character \n not displaying properly in textView Android

I know that if you do something like
myTextView.setText("This is on first line \n This is on second line");
Then it will display properly like this:
This is on first line
This is on second line
When I store that string in a database and then set it to the view it displays as such:
This is on first line \n This is on second line
Here is the line of code I use to extract the string from the database:
factView.setText(factsCursor.getString(MyDBAdapter.FACT_COLUMN));
I simply populate the database from a text file where each line is a new entry into the table so a line would look like this "This is on first line \n This is on second line" and it is stored as text.
Is there a reason that it isn't displaying the \n characters properly? It must be something to do with the string being in the database. Any suggestions?

I found this question Austyn Mahoney's answer is correct but here's a little help:
private String unescape(String description) {
return description.replaceAll("\\\\n", "\\\n");
}
description being the string coming out of your SQLite DB

As Falmarri said in his comment, your string is being escaped when it is put into the database. You could try and unescape the string by calling String s = unescape(stringFromDatabase) before you place it in your TextView.
As a side note, make sure you are using DatabaseUtils.sqlEscapeString() on any kind of data that is from the user or an unknown changeable source when inserting data into the database. This will protect you from errors and SQL Injection.

Try \\n instead of \n. If it throws an exception than use newline keyword in place of \n....newline is one character, ascii 10; it's often entered in a string literal...and will serve your purpose....:)

"This is on first line"||x'0A'||"This is on second line"
The || concatenates strings and the x'0A' is an unescaped newline.
If you're inserting records you'll have to replace every newline with "||x'0A'||" (If your string is double quoted). This may seem clumsy compared to the other asnswers. However if your lines are in separate columns this also works in a select:
SELECT firstline||x'0A'||secondline FROM wherever;
I found this while having the same problem you are: http://www.mail-archive.com/sqlite-users#sqlite.org/msg43557.html

A text area can be in multi line or single line mode. When it is in single line mode newline characters '\n' will be treated as spaces. When in doubt, to switch multi line mode on you can use the following code:
setInputType(getInputType() | InputType.TYPE_TEXT_FLAG_MULTI_LINE);
I had the problem that the same code did not work on honeycomb and on froyo, which seem to have different defaults. I am now also excluding the flag when I want to force a field to be single lined.
From the Android doc:
public static final int TYPE_TEXT_FLAG_MULTI_LINE Added in API level 3
Flag for TYPE_CLASS_TEXT: multiple lines of text can be entered into
the field. If this flag is not set, the text field will be
constrained to a single line. Constant Value: 131072 (0x00020000)
http://developer.android.com/reference/android/text/InputType.html#TYPE_TEXT_FLAG_MULTI_LINE
You have to set the flag before you populate the field.