I am trying to read the data from CSV file. everything works fine but when i try to read the data for longitude and latitude. it gives me an below error message.
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.yogi.guestlogix/com.example.yogi.guestlogix.MainActivity}: java.lang.NumberFormatException: Invalid double: "EVE"
Caused by: java.lang.NumberFormatException: Invalid double: "EVE"**
MainActivity.java
//Airports data begin
InputStream isss = getResources().openRawResource(R.raw.airports);
BufferedReader readerss = new BufferedReader(
new InputStreamReader(isss, Charset.forName("UTF-8"))
);
String liness = "";
//for airports.csv
try {
readerss.readLine();
while ((liness = readerss.readLine()) != null) {
//split by ',' first
String[] airport = liness.split(",");
//Read the data
AirportsData airdata = new AirportsData();
airdata.setAirportname(airport[0]);
airdata.setAirportcity(airport[1]);
airdata.setAirportcountry(airport[2]);
airdata.setAirportIATAcode(airport[3]);
//airdata.setAirportlang(Double.parseDouble(airport[4]));
//airdata.setAirportlat(Double.parseDouble(airport[5]));
AirportsDatas.add(airdata);
}
} catch (IOException e) {
Log.wtf("My Activity", "Reading data file error " + liness, e);
e.printStackTrace();
}
Log.d("Airline", "name is " + AirportsDatas);
AirportsData.java
public double getAirportlang(double airportlang) {
return airportlang;
}
public void setAirportlang(double airportlang) {
this.airportlang = airportlang;
}
public double getAirportlat( ) {
return airportlat;
}
public void setAirportlat(double airportlat) {
this.airportlat = airportlat;
}
#Override
public String toString() {
return "AirportsData{" +
"airportname='" + airportname + '\'' +
", airportcity='" + airportcity + '\'' +
", airportcountry='" + airportcountry + '\'' +
", airportIATAcode='" + airportIATAcode + '\'' +
", airportlang=" + airportlang +
", airportlat=" + airportlat +
'}';
}
**Any solution for this problem would be greatly appreciated....
The problem with CSV files is, that users (and other programmers) can pretty much write into the file what they want.
In your case, somebody entered a non-number into a CSV cell where you were expecting a double floating point number. Java correctly complains that this cannot be parsed to double. You have two approaches, to treat such situations:
A) Design by Contract
First, you could resolve that by relying on design by contract. You could have a parseLat method:
public Double parseLat(String[] csvRow) {
final String lat= csvRow[4];
assertIsNumeric(lat);
}
private void assertIsNumeric(String lat) {
if(!isNumeric(lat)) {
throw new IllegalArgumentException("Lattitude '" + lat + "' is not numeric");
}
}
There are countless options to implement an isNumeric method, some are discussed here. This will still stop the execution, but it will give a clearer message to users.
B) Defensive Design
A second option, is to provide a parseLAttitude method, that replaces non numeric value with null:
public Double parseLattitude(String[] csvRow) {
final String lattitude = csvRow[4];
if(!isNumeric(lattitude)) {
System.out.println("Could not parse lattitude '" + lat + "'");
return null;
}
return Double.parseDouble(lat);
}
I think the problem is that airport[4] & airport[5] might not be the lon and lat of the airport. If these field contain alpha characters [a-z] you will get an numberFormatException. Can you add the the output when you print airport like:
System.out.println(Arrays.asList(airport));
to the question? Than we will be better able to help you
Related
I have never done anything in java before so I really am a newb but while building the program I have ran into a snag that i just can't figure out. I will try to explain and show to the best of my abilities.
Here is what I am building
The UI
Here is the code I have so far to make it work.
private void jButtonGenerateActionPerformed(java.awt.event.ActionEvent evt) {
String ObjectName = jtObjectName.getText();
String ObjectBase = jcbBaseNPC.getSelectedItem().toString();
String NPCName = jtNPCName.getText();
String MinLevel = jtMinLevel.getText();
if (MinLevel != null && MinLevel.isEmpty())
MinLevel = MinLevel.replace(MinLevel, "minLevel" + MinLevel);{
}
//Alignment Combo Box Start
String Alignment = jcbAlignment.getSelectedItem().toString();
if (Alignment.contains("Good")) {
Alignment = Alignment.replace("Good", "255");
}
if (Alignment.contains("Neutral")) {
Alignment = Alignment.replace("Neutral", "127");
}
if (Alignment.contains("Evil")) {
Alignment = Alignment.replace("Evil", "0");
}
//Alignment Combo Box End
// Print to Output Box
jaOutput.append("object" + " " + ObjectName + " " + "of" + " " + ObjectBase +
"\n\tproperties" + "\n\tname" +" " + "\"" + NPCName + "\"" + MinLevel
);
What I can not understand it how to check to see if there is something entered in a String and if there is I need to add to it so the output looks like this.
minLevel 1100
maxLevel 1500
only thing I will be adding is the numbers so i need to add something like
minLevel + MinLevel
and if it is empty just skip it all together. If I add it to the append and its empty I will just get minLevel and i can't have it like that.
Any tips would be great.
Thank you all
Donald
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 7 years ago.
I have a problem right now in my program where a Student class is allowed 1 book and it must be stored in a variable _book however I can not seem to find a way to check if an object has already been instantiated or not without getting a run time error.
I have tried
Comparing variable to null
Accessing a function inside the variable that checks if the variable is null
Accessing a function inside the variable that checks if variable is 0
Simplified Code:
Student Class
public class Student {
private String _name;
private Library _collegeLibrary;
private LibraryCard _card;
private TextBook _book;
public Student(String name, Library library) {
_name = name;
_collegeLibrary = library;
System.out.println("[Student] Name: " + _name);
}
public void describe() {
String message;
message = "[Student] " + _name;
if (_book.returnTitle() == null) // returns java.lang.NullPointerException
message += " does not have a book";
else {
message += " is borrowing the book \"" + _book.returnTitle() + "\"";
}
System.out.println(message);
}
}
TextBook Class
public class TextBook {
String _title;
public TextBook(String title) {
_title = title;
}
public String returnTitle() {
return _title;
}
}
The above code will give me a java.lang.NullPointerException. I looked into catching the error however it doesn't seem like that is recommended.
You are checking if _book.returnTitle() is null, however, this doesn't take in account for _book being null. You can check if _book is null instead. That should fix your nullpointer exception.
Also, you should always wrap your if-else clauses in curly brackets. That way it's easier to read.
Change this section of your code:
if (_book.returnTitle() == null) // returns java.lang.NullPointerException
message += " does not have a book";
else {
message += " is borrowing the book \"" + _book.returnTitle() + "\"";
}
To this:
if (_book == null) { // returns java.lang.NullPointerException
message += " does not have a book";
} else {
message += " is borrowing the book \"" + _book.returnTitle() + "\"";
}
Also, as a tip, you can override the toString function to do exactly what your describe function does:
#Override
public String toString() {
String message;
message = "[Student] " + _name;
if (_book == null) { // returns java.lang.NullPointerException
message += " does not have a book";
} else {
message += " is borrowing the book \"" + _book.returnTitle() + "\"";
}
return message;
}
Usage:
public class SomeClass {
public static void main(String[] args) {
Student student = new Student("Student", new Library());
System.out.println(student); //Because you override #toString() you can just println the Student object.
}
}
I have a string, let's call it output, that's equals the following:
ltm data-group internal str_testclass {
records {
baz {
data "value 1"
}
foobar {
data "value 2"
}
topaz {}
}
type string
}
And I'm trying to extract the substring between the quotes for a given "record" name. So given foobar I want to extract value 2. The substring I want to extract will always come in the form I have prescribed above, after the "record" name, a whitespace, an open bracket, a new line, whitespace, the string data, and then the substring I want to capture is between the quotes from there. The one exception is when there is no value, which will always happen like I have prescribed above with topaz, in which case after the "record" name there will just be an open and closed bracket and I'd just like to get an empty string for this. How could I write a line of Java to capture this? So far I have ......
String myValue = output.replaceAll("(?:foobar\\s{\n\\s*data "([^\"]*)|()})","$1 $2");
But I'm not sure where to go from here.
Let's start extracting "records" structure with following regex ltm\s+data-group\s+internal\s+str_testclass\s*\{\s*records\s*\{\s*(?<records>([^\s}]+\s*\{\s*(data\s*"[^"]*")?\s*\}\s*)*)\}\s*type\s*string\s*\}
Then from "records" group, just find for sucessive match against [^\s}]+\s*\{\s*(?:data\s*"(?<data>[^"]*)")?\s*\}\s*. The "data" group contains what's you're looking for and will be null in "topaz" case.
Java strings:
"ltm\\s+data-group\\s+internal\\s+str_testclass\\s*\\{\\s*records\\s*\\{\\s*(?<records>([^\\s}]+\\s*\\{\\s*(data\\s*\"[^\"]*\")?\\s*\\}\\s*)*)\\}\\s*type\\s*string\\s*\\}"
"[^\\s}]+\\s*\\{\\s*(?:data\\s*\"(?<data>[^\"]*)\")?\\s*\\}\\s*"
Demo:
String input =
"ltm data-group internal str_testclass {\n" +
" records {\n" +
" baz {\n" +
" data \"value 1\"\n" +
" }\n" +
" foobar {\n" +
" data \"value 2\"\n" +
" }\n" +
" topaz {}\n" +
" empty { data \"\"}\n" +
" }\n" +
" type string\n" +
"}";
Pattern language = Pattern.compile("ltm\\s+data-group\\s+internal\\s+str_testclass\\s*\\{\\s*records\\s*\\{\\s*(?<records>([^\\s}]+\\s*\\{\\s*(data\\s*\"[^\"]*\")?\\s*\\}\\s*)*)\\}\\s*type\\s*string\\s*\\}");
Pattern record = Pattern.compile("(?<name>[^\\s}]+)\\s*\\{\\s*(?:data\\s*\"(?<data>[^\"]*)\")?\\s*\\}\\s*");
Matcher lgMatcher = language.matcher(input);
if (lgMatcher.matches()) {
String records = lgMatcher.group();
Matcher rdMatcher = record.matcher(records);
while (rdMatcher.find()) {
System.out.printf("%s:%s%n", rdMatcher.group("name"), rdMatcher.group("data"));
}
} else {
System.err.println("Language not recognized");
}
Output:
baz:value 1
foobar:value 2
topaz:null
empty:
Alernatives: As your parsing a custom language, you can give a try to write an ANTLR grammar or create Groovy DSL.
Your regex shouldn't even compile, because you are not escaping the " inside your regex String, so it is ending your String at the first " inside your regex.
Instead, try this regex:
String regex = key + "\\s\\{\\s*\\n\\s*data\\s*\"([^\"]*)\"";
You can check out how it works here on regex101.
Try something like this getRecord() method where key is the record 'name' you're searching for, e.g. foobar, and the input is the string you want to search through.
public static void main(String[] args) {
String input = "ltm data-group internal str_testclass { \n" +
" records { \n" +
" baz { \n" +
" data \"value 1\" \n" +
" } \n" +
" foobar { \n" +
" data \"value 2\" \n" +
" }\n" +
" topaz {}\n" +
" } \n" +
" type string \n" +
"}";
String bazValue = getRecord("baz", input);
String foobarValue = getRecord("foobar", input);
String topazValue = getRecord("topaz", input);
System.out.println("Record data value for 'baz' is '" + bazValue + "'");
System.out.println("Record data value for 'foobar' is '" + foobarValue + "'");
System.out.println("Record data value for 'topaz' is '" + topazValue + "'");
}
private static String getRecord(String key, String input) {
String regex = key + "\\s\\{\\s*\\n\\s*data\\s*\"([^\"]*)\"";
final Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(input);
if (matcher.find()) {
//if we find a record with data return it
return matcher.group(1);
} else {
//else see if the key exists with empty {}
final Pattern keyPattern = Pattern.compile(key);
Matcher keyMatcher = keyPattern.matcher(input);
if (keyMatcher.find()) {
//return empty string if key exists with empty {}
return "";
} else {
//else handle error, throw exception, etc.
System.err.println("Record not found for key: " + key);
throw new RuntimeException("Record not found for key: " + key);
}
}
}
Output:
Record data value for 'baz' is 'value 1'
Record data value for 'foobar' is 'value 2'
Record data value for 'topaz' is ''
You could try
(?:foobar\s{\s*data "(.*)")
I think the replaceAll() isn't necessary here. Would something like this work:
String var1 = "foobar";
String regex = '(?:' + var1 + '\s{\n\s*data "([^"]*)")';
You can then use this as your regex to pass into your pattern and matcher to find the substring.
You can simple transform this into a function so that you can pass variables into it for your search string:
public static void SearchString(String str)
{
String regex = '(?:' + str + '\s{\n\s*data "([^"]*)")';
}
I am working on an assignment with an online Udacity course, where we have been asked to develop a method that recognizes the last letter of the noun and then based on the letter, out put a "La", "el", or "?" + the noun.
The complete instructions are You are to complete the method fixNoun in the SpanishWord class so that it returns the noun preceded by:
// "la " if the noun ends in "a",
// "el " if it ends in "o"
// "? " if it ends in some other letter.
I seem to keep getting all failures when compiling. Can someone please help me understand what I am doing wrong?
public String fixNoun(String noun) {
String determinenet= noun.substring(noun.length() - 1);
if(determinenet.equals("a")) {
System.out.println("la" + " "+noun );
}
else if ( determinenet.equals("o")) {
System.out.println( "el"+ " "+noun);
}
else {
System.out.println("?"+ " "+noun);
}
return noun;
}
you don't return the altered noun but the old one. In your code you have to change the
System.out.println("la" + " "+noun );
to
return("la " + noun);
and so on.
The fixed code looks like this:
public String fixNoun(String noun) {
String determinenet= noun.substring(noun.length() - 1);
if(determinenet.equals("a")) {
return("la" + " "+noun );
}
else if ( determinenet.equals("o")) {
return( "el"+ " "+noun);
}
else {
return("?"+ " "+noun);
}
}
}
P.S.: The String class has a method endsWith() that gives you the last character of the string.
So you also could write your code like this:
public String fixNoun(String noun) {
if(noun.endsWith("a")) {
return("la " + noun);
else if(noun.endsWith("o")) {
return("el " + noun);
else {
return("? " + noun);
}
}
Good luck with your assignment :)
I don't know maybe i'm wrong. how about this?
String de=noun.charAt(noun.length()-1)
if(de.equalsIgnoreCase("a"))
return "la" + " "+noun ;
I'm writing something similar to smarterChild (that automated AOL Instant Messenger chat program from back in the day) and was curious about my method of determining sentence structure and response.
Currently, the bare bones design is to use 5 main methods which collectively determine the appropriate response given the user input:
1) Read(): initially accepts user input, then calls first of many methods: sentenceType()
2) getSentenceType(): User sentence type: Question, statement, directive, suggestion, etc…
3) getWho(): If question is about the computer, or about someone else…
4) getCategory(): What category the question is about (weather, sports…)
5) getResponse(): finally, form a response
These methods will query a database to determine if the user input contains key words...
Example of getSentenceType():
public String getSentenceType(String sentence) {
String type = null;
for (String s : db.getQuestions()) {
if (sentence.contains(s)) {
type = "question";
break;
}
else {
type = "statement";
}
}
return getWho(type, sentence);
}
Example of the final method which returns sentence structure:
//final call...
public String getResponse(String cat, String who, String type) {
String response = new String();
String auxVerb, subject, mainVerb, noun;
auxVerb = "do";
subject = who;
mainVerb = "like";
noun = cat;
//question structure: auxiliary verb + subject + main verb + noun/pronoun
// DO YOU LIKE MARY?
if (type.equals("question")) {
response = subject + " " + auxVerb + " " + mainVerb + " " + noun + ". ";
}
else {
response = auxVerb + " " + subject + " " + mainVerb + " " + noun + "?";
}
return response;
}
Sample database methods:
public String[] getQuestions() {
String[] questions = new String[] {"why", "?"};
return questions;
}
public String[] getWeather() {
String[] weather = new String[] {"cold", "hot", "rainy", "weather"};
return weather;
}
It will then progressively concatenate all the method results into a coherent response… then send that result back to Read(), which will print out the result to the user...
Is this an inefficient way to go about this? I know that if I continue down this path... to make a robust system, it will take tons of if else checks and a massive database to determine every possible type of response for user input.
Are there any suggested methods?
Thank you