Develop Reference

Need to round off two points after decimal digit

I'm working on an app and facing an issue. I've tried a number of solutions but nothing solved my problem.
I need to round off two digits after decimal point.
For Example.
9.225 should be rounded off to 9.23
Thank you.

For Kotlin use "%.2f".format(number), for Java use String.format("%.2f", number)
Result:

You can use String.format("%.2f", d), this will rounded automatically. d is your value.
OR
You can use this
double d = 1.234567;
DecimalFormat df = new DecimalFormat("#.##");
Log.d(df.format(d));
You can get as a float value as well like below.
float value = Float.valueOf(df.format(d)); // Output will be 1.24

I would have gone with a probable over the top solution however this is what i came up with.
It uses regex to split the string value of the number passed and then rounds up/down depending on the leading digit after the decimal place. It will return a Double in the instance but you can change that if you like. It does throw IllegalArgumentException, but thats taste dependant.
/**
* #param value the value that is being transformed
* #param decimalPlace the decimal place you want to return to
* #return transformed value to the decimal place
* #throws IllegalArgumentException
*/
Double roundNumber(#NonNull Double value, #NonNull Integer decimalPlace) throws IllegalArgumentException {
String valueString = value.toString();
if(valueString.length()> decimalPlace+1){
throw new IllegalArgumentException(String.format("The string value of %s is not long enough to have %dplaces", valueString, decimalPlace));
}
Pattern pattern = Pattern.compile("(\\d)('.')(\\d)");
Matcher matcher = pattern.matcher(valueString);
if (matcher.groupCount() != 4) { //0 = entire pattern, so 4 should be the total ?
throw new IllegalArgumentException(String.format("The string value of %s does not contain three groups.", valueString));
}
String decimal = matcher.group(3);
int place = decimal.charAt(decimalPlace);
int afterDecimalPlace = decimal.charAt(decimalPlace + 1);
String newDecimal = decimal.substring(0, decimalPlace - 1);
newDecimal += afterDecimalPlace > 5 ? (place + 1) : place;
return Double.parseDouble(matcher.group(1) + "." + newDecimal);
}

Converting string with time to minutes

I am working on an Android app that gets a time (duration) value as string.
For example, the app can get a value like: 6 hours 43 mins
or a value like: 15 mins
I am looking for a way to convert this strings to an integer value in minutes.
I have tried using this function, but I can´t extract the needed values:
str = str.replaceAll("[^\\d.]", "");
Edit:
it could be possible a result like 6 hours, the only known condition is that minutes are always rounded to an integer, the minimum value is 1 min

Using a Regex to get each couple numeric/time_unit. You can easily parse that with :
(\\d+) (\\w+)
Group 1 : numeric value
Group 2 : time unit
(note that I used a space between the two (could be optional if you want)
Using Java Pattern class to use that regex
Pattern p = Pattern.compile("(\\d+) (\\w+)");
Then you just have to iterate on each match to get the couple type/value
Matcher m = p.matcher(s);
while(m.find()){
String type = m.group(2);
int value = Integer.parseInt(m.group(1))
...
}
From that, just use a switch to convert the number into minute and add it to the variable, omitting the break to have a nice (but not efficient) converter :
switch(type){
//Add more time unit in the correct order if needed
case "days":
value *= 24;
case "hours":
value *= 60;
case "mins":
mins += value;
break;
}
Each type will convert the value into a correct number of minute, at the end, you will have the result in minutes.

Problem: There are few concerns as you never know without putting extra conditions like:
15 hours and 15 mins both will be stored in same integer value , you eventually need to differentiate them on some conditions to cater all the issues.
Coming to the question, you may achieve all this by using String split cases but you need to manually cater all the cases keeping in mind a user can use any spell words like hours can be hrs and so on

You could split the String at the whitespace and use the values in the array.
String value1 = "6 hours 43 mins";
String value2 = "15 mins";
String[] resultList1 = value1.split(" ");
String[] resultList2 = value2.split(" ");
int minutes1 = 0;
int minutes2 = 0;
if(resultList1.length == 4) {
minutes1 = Integer.parseInt(resultList1[0]) * 60 + Integer.parseInt(resultList1[2]);
} else {
minutes1 = Integer.parseInt(resultList1[0]);
}
if(resultList2.length == 4) {
minutes2 = Integer.parseInt(resultList2[0]) * 60 + Integer.parseInt(resultList2[2]);
} else {
minutes2 = Integer.parseInt(resultList2[0]);
}
System.out.println(minutes1);
System.out.println(minutes2);
The result is:
403
15

Either String split() or Pattern Matcher, as earlier answers suggest, will work. I'm not sure which will be more efficient though, but it's probably irrelevant in this case. My version:
String timeStr = "2 hours 15 mins";
String[] parts = timeStr.split(" ");
int totalMins = 0;
for(int i=1; i< parts.length; i+=2) {
// Add checking for "days", etc., if necessary.
if(parts[i].equals("hours")) {
int h = Integer.parseInt(parts[i-1]);
totalMins += 60 * h;
} else if(parts[i].equals("mins")) {
int m = Integer.parseInt(parts[i-1]);
totalMins += m;
}
}
System.out.println("totalMins = " + totalMins);
>> totalMins = 135

If you can get each minute and hours separately you can use string.replace("mins", "") then use Integer.parseInt().
If you get overral like 6 hours 43 mins you must split the string.

I am not sure whether this can be done in a single regex, but if I were you I would use a different regex to find the number of hours, the number of minutes, the number of seconds, etc.
Given a string in the format you mentioned, you can first extract the number of hours by using this regex:
\d+(?= hours?)
Then extract the number of minutes:
\d+(?= mins?)
If seconds can appear in the input string, you can use this to extract seconds as well:
\d+(?= secs?)
If any of the regexes don't match, that means there isn't that information in the string.

String time = "6 hours 43 mins";//or (43 mins) or (6 hours)
int h, m;
String[] parts = time.split(" ");
if (parts.length == 4) {
h = parts[1];
m = parts[3];
} else if (parts.length == 2) {
if (parts[1].isEqualTo("hours") {
h = parts[0];
} else if (parts[1].isEqualTo("mins") {
m = parts[0];
}
}
return h*60+m;

How to get byte by byte from byte array

I am getting response from server in string format like
V1YYZZ0x0000010x0D0x00112050x0C152031962061900x0D410240x0E152031962061900x0F410240x1021TATADOCOMOINTERNET101
Then I am converting it in to byte array because i need to get value from this byte by byte.
I tried to use
Arrays.copyOfRange(original,
from , to);
but it work on index basis not on byte basis.
I also tried following solution but it also truncating String(if I use string instead of byte[]) on length basis.
public static String truncateWhenUTF8(String s, int maxBytes) {
int b = 0;
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
// ranges from http://en.wikipedia.org/wiki/UTF-8
int skip = 0;
int more;
if (c <= 0x007f) {
more = 1;
} else if (c <= 0x07FF) {
more = 2;
} else if (c <= 0xd7ff) {
more = 3;
} else if (c <= 0xDFFF) {
// surrogate area, consume next char as well
more = 4;
skip = 1;
} else {
more = 3;
}
if (b + more > maxBytes) {
return s.substring(0, i);
}
b += more;
i += skip;
}
return s;
}
I know how to calculate string in byte length but it giving only full string length in byte like
Here is how I need to extract packet on byte basis.
Above codes and parameters is only example. I need to get byte by byte from string/byte array.
I searched lot but didn't get any solution or link which I can refer. I am not getting how to split string using byte length because I know byte length for each parameter and for value also.
Please give me any reference or hint.

To determine what is equal to one byte in a String is not trivial. Your String contains bytes in hexadecimal text form: 0x0D (one byte, equal to 13), but also contains values as substrings. For example 1024 can be interpreted as an integer which in this case fits into 2 bytes, but could also be interpreted as a text made up by 4 chars, totaling to 8 bytes.
Anyways, I would split the string using a regular expression, and then further split the parts to length and value:
String message = "V1YYZZ0x0000010x0D0x00112050x0C152031962061900x0D41024"+
"0x0E152031962061900x0F410240x1021TATADOCOMOINTERNET101";
String regex = "(0)(x)(\\w\\w)";
String[] parts = message.split(regex);
Log.d(TAG,"HEADER = "+parts[0]);
for (int i=1; i<parts.length; i++) {
String s = parts[i];
// Only process if it has length > 0
if (s.length()>0) {
String len = "", val = "";
// String s is now in format LVVVV where L is the length, V is the value
if (s.length() < 11) {
// 1 character indicates length, up to 9 contains value
len = s.substring(0, 1);
val = s.substring(1);
} else if (s.length() > 10) {
// 2 characters indicate length, up to 99 contains value
len = s.substring(0, 2);
val = s.substring(2);
} else if (s.length() > 101) {
// 3 characters indicate length, up to 999 contains value
len = s.substring(0, 3);
val = s.substring(3);
}
Log.d(TAG, "Length: " + len + " Value: " + val);
}
}
This produces the following output:
D/Activity: HEADER = V1YYZZ
D/Activity: Length: 0 Value: 001
D/Activity: Length: 1 Value: 1205
D/Activity: Length: 15 Value: 203196206190
D/Activity: Length: 4 Value: 1024
D/Activity: Length: 15 Value: 203196206190
D/Activity: Length: 4 Value: 1024
D/Activity: Length: 21 Value: TATADOCOMOINTERNET101
Then you can check the packages (the first two package in the header is not needed), convert Strings to whatever you would like (e.g. Integer.parseInt(val))
If you explain the structure of the header (V1YYZZ0x0000010x0D0x0011205), I can improve my answer to find the message count.

I think it is doable with Scanner
import java.util.Scanner;
public class Library {
public static void main(String[] args) {
String s = "V1YYZZ0x0000010x0D0x001120"
+ "50x0C152031962061900x0D410240x0E152031962061900x0F410240x1"
+ "021TATADOCOMOINTERNET101";
// Skip first 9? bytes. I'm not sure how you define them
// so I just assumed it is 26 chars long.
s = s.substring(26, s.length());
System.out.println(s);
Scanner scanner = new Scanner(s);
// Use byte as delimiter i.e. 0xDC, 0x00
// Maybe you should use smth like 0x[\\da-fA-F]{2}
// And if you want to know that byte, you should use
// just 0x and get first 2 chars later
scanner.useDelimiter("0x\\w{2}");
// Easily extracted
int numberOfParams = scanner.nextInt();
for (int i = 0; i < numberOfParams; i++) {
String extracted = scanner.next();
// Length of message
int l = extracted.length();
boolean c = getLength(l) == getLength(l - getLength(l));
l -= getLength(l);
l = c ? l : l-1;
System.out.println("length="
+ extracted.substring(0, extracted.length()-l));
System.out.println("message="
+ extracted.substring(extracted.length()-l, extracted.length()));
}
// close the scanner
scanner.close();
}
// Counting digits assuming number is decimal
private static int getLength(int l) {
int length = (int) (Math.log10(l) + 1);
System.out.println("counted length = " + length);
return length;
}
}
We definitely need more information about rules, how string is formed. And what exactly you need to do. This code might be good enough you. And without comments it is really short and simple.

This is not a answer to accessing a byte array byte by byte, but is an answer for the situation in which you find yourself.
Your explanation and description have the appearance of being confused as to what it is that you are really getting from the server (e.g. it is quite hard to represent "V1YYZZ0x0000010x0D0x001120" as a 9 byte field (note it probably ends on the 2, not the 0)). Alternately, that you are using the wrong method to get it from the server, or not getting it as the intended data type.
Your code indicates that you believe that what you are getting is a UTF8 string. The data shown in your question does not appear to indicate that it is intended to be in that format.
Keep in mind when doing something like this that some other programmer had to create structure for the data that you are seeing. They had to define it somewhere with the intent that it be able to be decoded by their intended recipients. Unless there are other considerations (security, minimal bandwidth, etc.), such formats are usually defined in a way that is both easy to encode and decode.
The existence of the multiple "0x"-ASCII-encoded hexadecimal numbers --particularly the single byte representing the parameter (called "varam" in your graphic)-- strongly implies that this data was intended to be interpreted as a ASCII encoded string. While that might not be the case, it should be kept in mind when looking at the problem from a larger perspective.
You are having to put too much effort into decoding the information you are getting from the server. It, probably, should be relatively easy unless there are considerations why it would have intentionally been made difficult.
All of this indicates that the real problem exists in an area for which you have provided us with no information.
Step back:
Think about things like:
How are you receiving this from the server (what function/interface)?
In the call requesting the information from the server is there a way to specify the encoding type be bytes, an ASCII string, or some other format that is easier to deal with than UTF8? At a minimum, it appears to be clear that the data was not intended to be handled as a UTF8 string. There should be a way for you to get it without it having been converted to UTF8.
Also, you should try to find an actual specification for the format of the data. You have not explained much about the source, so it may be you are reverse-engineering something and have no access to specifications.
Basically, it looks like this is a problem where it might be a good idea to step back and ask if you are starting from the point that makes it easiest to solve and if you are headed in the right direction for doing so.

I'm sure I'm missing something obvious...
String.getBytes();
And if you want to process it in order taking defined objects from the array, just wrap using
ByteBuffer.wrap();
The result being something along the lines of:
String s = "OUTPUT FROM SERVER";
byte[] bytes = s.getBytes();
ByteBuffer bb = ByteBuffer.wrap(bytes);
What did I miss from the initial question? :/

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
}

Processing large files on Android

I am writing an android app which requires me to process a very large file(say 50MB). The file contains three entries-A userid, artistid and the number of times the user has listened to that artist. So now I write the code to find out who the most popular artist is based on the number of times the artist has been heard. I achieve this by hashmapping each of the artist id(key) and then the number of times he's been heard (value).
The code works fine as long as the file is below 20B (I run the app on Nexus S 4g, so the heap is 32MB), but I get an 'Out of memory' error for larger files. I realize the code is very badly written. Any suggestions as to how I could get through this problem!
while ((text = inRd.readLine()) != null) {
StringTokenizer st = new StringTokenizer(text);
while (st.hasMoreTokens()) {
int userid = Integer.parseInt(st.nextToken());
artistid = Integer.parseInt(st.nextToken());
int no_times = Integer.parseInt(st.nextToken());
if (hm.containsKey(artistid)) {
Integer oldval = (Integer) hm.get(artistid);
Integer newval = no_times + oldval;
hm.remove(artistid);
hm.put(artistid, newval);
} else
hm.put(artistid, no_times);
}
}

A hashmapping is not the most efficient way to store things. Try a Vector or straight arrays.
Hope this Helps
Cliff