Develop Reference

Java (Android) - can't detect first character of string?

Not sure if I've missed something really obvious. I know for sure that my String is as follows:
1This is a test message
I'm trying to detect whether the first character is '1', so here's some of my code:
//This outputs '1'
Toast noCmd = Toast.makeText(Play.this, decodedMessage.substring(0,1), Toast.LENGTH_SHORT);
noCmd.show();
if (decodedMessage.charAt(0) == 1) {
noCmd = Toast.makeText(Play.this, "This should show up", Toast.LENGTH_SHORT);
noCmd.show();
noCmd = Toast.makeText(Play.this, finalMessage + " from " + sender, Toast.LENGTH_SHORT);
noCmd.show();
}
if (decodedMessage.substring(0,1) == "1") {
noCmd = Toast.makeText(Play.this, "This should show up", Toast.LENGTH_SHORT);
noCmd.show();
noCmd = Toast.makeText(Play.this, finalMessage + " from " + sender, Toast.LENGTH_SHORT);
noCmd.show();
}
As you can see, I'm trying two methods to get the toasts inside the if statement to show up. Weirdly, when the code is run, only the top (unconditional) toast displays.
Any ideas?

For the first one, the char is '1'. What's currently happening in your code is that because you're comparing a char with an integer, the char is being converted to an int using its character code. For a 1, that comes out as 49, which is not equal to the integer 1. You need to compare the char you're retrieving from the String with the char representing a digit "1", and that means you need to write it as '1'.
For the second one, you need to use .equals() to test for String equality, rather than ==. If you take two String objects s and t that have the same content, then you still will find that s==t will come out as false, unless they happen to be pointing at the same bit of memory (i.e., they're the same instance). To check whether they have the same content, you check
s.equals(t)
rather than
s==t
So, in summary, make the first one
if (decodedMessage.charAt(0) == '1') {
//toast stuff
}
and the second one
if ("1".equals(decodedMessage.substring(0,1))) {
//toast stuff
}
The reason, by the way, for not writing
if (decodedMessage.substring(0,1).equals("1")) {
//toast stuff
}
instead is that if the String on which you call .equals() is null then you'll end up with a NullPointerException, which usually you want to avoid. Actually in this case it would be fine, because the substring() call won't return null, but in the general case if you want to test whether s and "something" are equal then you use
"something".equals(s)
rather than
s.equals("something")
just in case s is null.

1 is an integer with value 1. If you want the ASCII 1, use '1' in single quotes which has the integer value of 49.
For comparing strings, use equals() and not ==. See How do I compare strings in Java?

To compare strings you need to use equals method:
if("1".equals(decodedMessage.charAt(0))){
}

Separating the words after the last integer in a large String

I've seen many people do similar to this in order to get the last word of a String:
String test = "This is a sentence";
String lastWord = test.substring(test.lastIndexOf(" ")+1);
I would like to do similar but get the last few words after the last int, it can't be hard coded as the number could be anything and the amount of words after the last int could also be unlimited. I'm wondering whether there is a simple way to do this as I want to avoid using Patterns and Matchers again due to using them earlier on in this method to receive a similar effect.
Thanks in advance.

I would like to get the last few words after the last int.... as the number could be anything and the amount of words after the last int could also be unlimited.
Here's a possible suggestion. Using Array#split
String str = "This is 1 and 2 and 3 some more words .... foo bar baz";
String[] parts = str.split("\\d+(?!.*\\d)\\s+");
And now parts[1] holds all words after the last number in the string.
some more words .... foo bar baz

What about this one:
String test = "a string with a large number 1312398741 and some words";
String[] parts = test.split();
for (int i = 1; i < parts.length; i++)
{
try
{
Integer.parseInt(parts[i])
}
catch (Exception e)
{
// this part is not a number, so lets go on...
continue;
}
// when parsing succeeds, the number was reached and continue has
// not been called. Everything behind 'i' is what you are looking for
// DO YOUR STUFF with parts[i+1] to parts[parts.length] here
}

Extract code country from phone number [libphonenumber]

I have a string like this : +33123456789 (french phone number). I want to extract the country code (+33) without knowing the country. For example, it should work if i have another phone from another country. I use the google library https://code.google.com/p/libphonenumber/.
If I know the country, it is cool I can find the country code :
PhoneNumberUtil phoneUtil = PhoneNumberUtil.getInstance();
int countryCode = phoneUtil.getCountryCodeForRegion(locale.getCountry());
but I don't find a way to parse a string without to know the country.

Okay, so I've joined the google group of libphonenumber ( https://groups.google.com/forum/?hl=en&fromgroups#!forum/libphonenumber-discuss ) and I've asked a question.
I don't need to set the country in parameter if my phone number begins with "+". Here is an example :
PhoneNumberUtil phoneUtil = PhoneNumberUtil.getInstance();
try {
// phone must begin with '+'
PhoneNumber numberProto = phoneUtil.parse(phone, "");
int countryCode = numberProto.getCountryCode();
} catch (NumberParseException e) {
System.err.println("NumberParseException was thrown: " + e.toString());
}

I have got kept a handy helper method to take care of this based on one answer posted above:
Imports:
import com.google.i18n.phonenumbers.NumberParseException
import com.google.i18n.phonenumbers.PhoneNumberUtil
Function:
fun parseCountryCode( phoneNumberStr: String?): String {
val phoneUtil = PhoneNumberUtil.getInstance()
return try {
// phone must begin with '+'
val numberProto = phoneUtil.parse(phoneNumberStr, "")
numberProto.countryCode.toString()
} catch (e: NumberParseException) {
""
}
}

In here you can save the phone number as international formatted phone number
internationalFormatPhoneNumber = phoneUtil.format(givenPhoneNumber, PhoneNumberFormat.INTERNATIONAL);
it return the phone number as
International format +94 71 560 4888
so now I have get country code as this
String countryCode = internationalFormatPhoneNumber.substring(0,internationalFormatPhoneNumber.indexOf('')).replace('+', ' ').trim();
Hope this will help you

Here is a solution to get the country based on an international phone number without using the Google library.
Let me explain first why it is so difficult to figure out the country. The country code of few countries is 1 digit, 2, 3 or 4 digits. That would be simple enough. But the country code 1 is not just used for US, but also for Canada and some smaller places:
1339 USA
1340 Virgin Islands (Caribbean Islands)
1341 USA
1342 not used
1343 Canada
Digits 2..4 decide, if it is US or Canada or ... There is no easy way to figure out the country, like the first xxx are Canada, the rest US.
For my code, I defined a class which holds information for ever digit:
public class DigitInfo {
public char Digit;
public Country? Country;
public DigitInfo?[]? Digits;
}
A first array holds the DigitInfos for the first digit in the number. The second digit is used as an index into DigitInfo.Digits. One travels down that Digits chain, until Digits is empty. If Country is defined (i.e. not null) that value gets returned, otherwise any Country defined earlier gets returned:
country code 1: byPhone[1].Country is US
country code 1236: byPhone[1].Digits[2].Digits[3].Digits[6].Country is Canada
country code 1235: byPhone[1].Digits[2].Digits[3].Digits[5].Country is null. Since
byPhone[1].Country is US, also 1235 is US, because no other
country was found in the later digits
Here is the method which returns the country based on the phone number:
/// <summary>
/// Returns the Country based on an international dialing code.
/// </summary>
public static Country? GetCountry(ReadOnlySpan<char> phoneNumber) {
if (phoneNumber.Length==0) return null;
var isFirstDigit = true;
DigitInfo? digitInfo = null;
Country? country = null;
foreach (var digitChar in phoneNumber) {
var digitIndex = digitChar - '0';
if (isFirstDigit) {
isFirstDigit = false;
digitInfo = ByPhone[digitIndex];
} else {
if (digitInfo!.Digits is null) return country;
digitInfo = digitInfo.Digits[digitIndex];
}
if (digitInfo is null) return country;
country = digitInfo.Country??country;
}
return country;
}
The rest of the code (digitInfos for every country of the world, test code, ...) is too big to be posted here, but it can be found on Github:
https://github.com/PeterHuberSg/WpfWindowsLib/blob/master/WpfWindowsHelperLib/CountryCode.cs
The code is part of a WPF TextBox and the library contains also other controls for email addresses, etc. A more detailed description is on CodeProject: International Phone Number Validation Explained in Detail
Change 23.1.23: I moved CountryCode.cs to WpfWindowsHelperLib, which doesn't have any WPF dependencies, despite it's name.

Use a try catch block like below:
try {
const phoneNumber = this.phoneUtil.parseAndKeepRawInput(value, this.countryCode);
}catch(e){}

If the string containing the phone number will always start this way (+33 or another country code) you should use regex to parse and get the country code and then use the library to get the country associated to the number.

Here's a an answer how to find country calling code without using third-party libraries (as real developer does):
Get list of all available country codes, Wikipedia can help here:
https://en.wikipedia.org/wiki/List_of_country_calling_codes
Parse data in a tree structure where each digit is a branch.
Traverse your tree digit by digit until you are at the last branch - that's your country code.

Compare two things doesn't work

I have a strange problem in my android app. I must compare two string which are equals. I tried this :
if (raspunsdata.equals(rok)) {
System.out.println("changed ");
} else
System.out.println("no change");
}
but I get always "no change". Before this I have System.out.println for both strings, and both of them have the same value.
I tried also (raspunsdata==rok) and raspunsdata.contentEquals(rok) but I have the same problem. Why? I cant understand this.,...please help...

You might have unwanted white spaces. Might need to use the trim function just to make sure.
if (raspunsdata.trim.equals(rok.trim())) {
System.out.println("changed ");
} else
System.out.println("no change");
}
Btw equals is the correct way to check whether the values are the same.

.equals - compares the values of both objects. If you have 2 Strings with the same characters sets .equals will return true;
== - compares if two objects references are equal.
For example:
String a = "lol";
String b = a;
a == b - will be true.
Try reading: http://www.devdaily.com/java/edu/qanda/pjqa00001.shtml

Get phone number without country code for the purpose of comparing numbers

I can obtain the phone number from an incoming call or from a sms message. unfortunately, in case of the SMS there might be the country code in it. So, basically I need to obtain the plain phone number, without country code, in order to compare it with existing numbers in Contacts.

If you want to compare phone numbers you can always use the
PhoneNumberUtils.compare(number1, number2);
or
PhoneNumberUtils.compare(context, number1, number2);
Then you don't have to worry about the country code, it will just compare the numbers from the reversed order and see if they match (enough for callerID purposes at least).

fast untested approach (AFAIK phone numbers have 10 digits):
// As I said, AFAIK phone numbers have 10 digits... (at least here in Mexico this is true)
int digits = 10;
// the char + is always at first.
int plus_sign_pos = 0;
// Always send the number to this function to remove the first n digits (+1,+52, +520, etc)
private String removeCountryCode(String number) {
if (hasCountryCode(number)) {
// +52 for MEX +526441122345, 13-10 = 3, so we need to remove 3 characters
int country_digits = number.length() - digits;
number = number.substring(country_digits);
}
return number;
}
// Every country code starts with + right?
private boolean hasCountryCode(String number) {
return number.charAt(plus_sign_pos) == '+'; // Didn't String had contains() method?...
}
then you just call these functions