I am new to Java and practicing parsing csv file into the object. I've tried but cannot figure it out.
The file looks like this:
[0], [1], [2], [3] , [4] , [5] , [6] , [7] , [8] , [9]
class, gender, age, bodyType, profession, pregnant, isYou ,species, isPet, role
scenario:green, , , , , , , ,
person, female, 24, average , , FALSE , , , , passenger
animal, male , 4, , , FALSE , , dog , TRUE , pedestrian
scenario:red
person, male , 16, athletic, boxer , FALSE , TRUE , , , passenger
person, female, 25, athletic, doctor , TRUE , FALSE , , , pedestrian
I need to parse it by any number of passengers and pedestrians with any scenarios. Finally, add these scenarios into an ArrayList for analyzing.
What I think is to:
loop through each line, stops when reaches to the next scenario:red, adds the passengers and the pedestrians to the Character ArrayList. (I've done adding, but don't how to stop).
Create a scenario using constructor scenario(ArrayList<Character> passenger, ArrayList<Character> pedestrians, boolean redOrGreen);
The ArrayList scenarios add the created scenarios.
What I've done is put everything together instead of separate them. Any help or hint is highly appreciated.
Thanks for this community who helped me, here is what I've got so far.
public void loadCsv() throws IOException {
String csvFile = "config.csv";
String line = "";
String csvSplit = "\\s*,\\s*";
Scenario scenario = new Scenario();
Person person = new Person();
Animal animal = new Animal();
ArrayList<Scenario> scenaios = new ArrayList<Scenario>();
ArrayList<String> csvContents = new ArrayList<String>();
ArrayList<Character> passengers = new ArrayList<Character>();
ArrayList<Character> pedestrians = new ArrayList<Character>();
try (BufferedReader csvReader = new BufferedReader(new FileReader(csvFile));) {
String headerLine = csvReader.readLine(); //get rid of the header
//add each line to the arrayList
while ((line = csvReader.readLine()) != null) {
csvContents.add(line);
}
for(String csvLine : csvContents) {
String[] data = csvLine.split(csvSplit); // split by comma and remove redundant spaces
if (data.length == NO_OF_FIELD) { //check and avoid indexOutOfBoundException
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
if (clazz.startsWith("scenario") && data.length == 1) {
scenario = new Scenario();
scenario.setLegalCrossing(clazz.endsWith("green"));
continue;
}
else if ("person".equals(clazz) && data.length ==10) {
person = loadCsvPerson(data);
addCharacter(person, data);
}
else if ("animal".equals(clazz) && data.length ==10) {
animal = loadCsvAnimal(data);
addCharacter(animal, data);
}
}
}
}
//passenger and pedestrians are in position
System.out.println("passengers: " + passengers);
System.out.println("pedestrians: " + pedestrians);
if (null != scenario) {
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
If it is possible to change the csv file format, I would add scenario type column (and scenario id or name if required), so you can work with csv file as a result set from database when you join tables (scenario + passenger + pedestrian) and return plain rows.
With this approach you will be able to delegate parsing to any csv library and do your logic (group by scenario id/name/type) separately. With surrogate rows you have (scenario:green...) you have to write your custom parser.
For example, you can use univocity to simply parse file into your model (even using annotations) and iteratively group it and handle.
Or if you need to work with existing file format do something like that:
if (clazz.startsWith("scenario") && data.length == 1) {
// collect existing scenario before starting processing new one
if (scenario != null) {
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
passengers = new ArrayList();
pedestrians = new ArrayList();
scenarios.add(scenario);
}
// now start new group (scenario)
scenario = new Scenario();
scenario.setLegalCrossing(clazz.endsWith("green"));
continue;
}
Following things need to be addressed in your code:
Strive to avoid using the name of a class which is already used by the standard library (and especially when it is in the default package, java.lang) e.g. there is already a class Character in Java library and therefore you should use a different name for your custom class.
Use continue to skip the line, scenario:red
for(String csvLine : csvContents) {
if(csvLine.equals("scenario:red")){
continue;
}
String[] data = csvLine.split(csvSplit); // split by comma and remove redundant spaces
if (data.length == NO_OF_FIELD) {
//..
}
//..
}
If you have already defined final int NO_OF_FIELD = 10, you can use the same instead of using the value 10 directly i.e. you should use NO_OF_FIELD instead of 10 in the following code:
if (data.length == NO_OF_FIELD) { //check and avoid indexOutOfBoundException
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
//...
else if ("person".equals(clazz) && data.length ==10) {
However, you also need to understand that && data.length ==10 is unnecessary here as you have already checked data.length == NO_OF_FIELD in the enclosing if condition.
I couldn't understand the rest of your points. If you clarify them, I'll be able to help you further.
I need to add the previous scenario in the second round.
Since the last set of data won't be captured, I need to set another new scenario to add it in. Thanks for the art sir.
Character character = null;
try (BufferedReader csvReader = new BufferedReader(new FileReader(csvFile));) {
String headerLine = csvReader.readLine(); //get rid of the header
//add each line to the arrayList
while ((line = csvReader.readLine()) != null) {
csvContents.add(line);
}
final int NO_OF_FIELDS = 10;
for(String csvLine : csvContents) {
String[] data = csvLine.split(csvSplit); // split by comma and remove redundant spaces
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
if (clazz.startsWith("scenario") && data.length == 1) {
// adding scenario after one set of data
// i.e second round adding the first round data
if (passengers.size() != 0 && pedestrians.size() != 0) {
Scenario scenario = new Scenario();
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
scenarios.add(scenario);
}
passengers = new ArrayList<Character>();
pedestrians = new ArrayList<Character>();
if (clazz.endsWith("green")) {
scenario.setLegalCrossing(true);
System.out.println("green light");
}
else if (clazz.endsWith("red")){
scenario.setLegalCrossing(false);
System.out.println("red light");
}
continue;
}
//...
Scenario scenario = new Scenario();
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
scenarios.add(scenario);
scenario.setPassengers(passengers);
scenario.setPedestrians(pedestrians);
Audit audit = new Audit();
audit.setScenario(scenarios);
Related
I only want to check for:
if (lore.contains("§eSigned of ")) {
but it doesn't get that it does contain "§eSigned of "
I wrote a Minecraft Command /sign you can add a lore to an item ("Signed of playerrank | playername").
Then i wanted to add an /unsign command to remove this lore.
ItemStack is = p.getItemInHand();
ItemMeta im = is.getItemMeta();
List<String> lore = im.hasLore() ? im.getLore() : new ArrayList<String>();
if (lore.contains("§eSigned of " + getChatName(p))) { // this line is important!
for (int i = 0; i < 3; i++) {
int size = lore.size();
lore.remove(size - 1);
}
im.setLore(lore);
is.setItemMeta(im);
p.setItemInHand(is);
sendMessage(p, "§aThis item is no longer signed");
} else {
sendMessage(p, "§aThis item is not signed!");
}
return CommandResult.None;
Everything works fine until you e.g. change your name. than you can't remove the sign because getChatName(p) has changed.
To fix this i only want to check
if (lore.contains("§eSigned of ")) {
but than it doesn't get it and returns false. (it says lore does not contain "§eSigned of ")
I tried a lot but it only works with the string "§eSigned of " and getChatName(p).
As the documentation "contains" searches for the specific string so it should work as I thought right?
Add:
getChatName(p) returns the rank of the player and the playername like: "Member | domi"
sendMessage(p, "") sends a simple message in the Minecraft chat
The problem you run into is that contains(String) looks for a matching string. What you search for is a check if any string in the list starts with "§eSigned of ".
I would suggest adding a function isSignedItem like this:
private boolean isSignedItem(List<String> lore) {
for (String st : lore)
if (st.startsWith("§eSigned of "))
return true;
return false;
}
and then to use this function to check if the item is signed or not:
[...]
List<String> lore = im.hasLore() ? im.getLore() : new ArrayList<String>();
if (isSignedItem(lore)) { // this line is important!
for (int i = 0; i < 3; i++) {
int size = lore.size();
lore.remove(size - 1);
}
[...]
I am new to Java and practice parsing csv file. I do understand what does IndexOutOfBound means, but I don't understand why my parsed data cannot do like all the tutorials I've visited such as https://examples.javacodegeeks.com/java-csv-parsing-example/
I can only read the first column, which is data[0]. There must be something wrong with my parsing method, but I cannot figure it out. Any help or hint is hight appreciated.
my data file looks like this:
[0], [1], [2], [3] , [4] , [5] , [6] , [7] , [8] , [9]
class, gender, age, bodyType, profession, pregnant, isYou ,species, isPet, role
scenario:green, , , , , , , ,
person, female, 24, average , doctor , FALSE , , , , passenger
animal, male , 4, , , FALSE , , dog , TRUE , pedestrian
.
.
I tried to parse like this:
ArrayList<String> csvContents = new ArrayList<String>();
try (BufferedReader csvReader = new BufferedReader(new FileReader(csvFile));) {
String headerLine = csvReader.readLine(); //get rid of header
while ((line = csvReader.readLine()) != null) {
csvContents.add(line);// add the line to the ArrayList
}
for (String csvLine : csvContents) {
// split by comma and remove redundant spaces
String[] data = csvLine.split("\\s*,\\s*");
System.out.println(data[1]);// IndexOutOfBound
Character character = null;
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
Profession professionEnum = Profession.valueOf(data[4].toUpperCase());
Gender genderEnum = Gender.valueOf(data[1].toUpperCase());
BodyType bodyTypeEnum =BodyType.valueOf(data[3].toUpperCase());
if (clazz.startsWith("scenario")) {
scenario = new Scenario();
scenario.setLegalCrossing(clazz.endsWith("green"));
continue;
} else if ("person".equals(clazz)) {
person = new Person(Integer.parseInt(data[2]), professionEnum ,genderEnum , bodyTypeEnum , Boolean.parseBoolean(data[5]));
person.setAsYou(Boolean.parseBoolean(data[6]));
} else if ("animal".equals(clazz)) {
animal = new Animal(Integer.parseInt(data[2]) , genderEnum , bodyTypeEnum, data[7]);
animal.setIsPet(Boolean.parseBoolean(data[8]));
}
} catch (someException e) {
e.printStackTrace();
}
EDIT
print out csvLine before split:
scenario:green,,,,,,,,,
person,female,24,average,doctor,false,false,,,passenger
person,male,40,overweight,unknown,false,false,,,passenger
person,female,2,average,,false,false,,,passenger
person,male,82,average,,false,false,,,pedestrian
person,female,32,average,ceo,true,false,,,pedestrian
person,male,7,athletic,,false,false,,,pedestrian
animal,male,4,,,false,false,dog,true,pedestrian
scenario:red,,,,,,,,,
After spliting, the data just have one element, so that when you access data[1], then you get exception.
Solution: try with another regex like "," only.
Ps: your csv is malformed at
scenario:green, , , , , , , ,
Try to put one more ","
you need to fill comlete data for all cells in a row.
For eg. first line in your csv, contains only 1 cell having value scenario:green which is data[0].
If you fill in data for all other cells in your csv, your will start receiving data[1], data[2], data[3]....
I've figured it out. It's counterintuitive for me, though. I need to specify the length of the data array parsed to put every attribute like this:
ArrayList<String> csvContents = new ArrayList<String>();
try (BufferedReader csvReader = new BufferedReader(new FileReader(csvFile));) {
String headerLine = csvReader.readLine(); //get rid of header
while ((line = csvReader.readLine()) != null) {
csvContents.add(line);// add the line to the ArrayList
}
for (String csvLine : csvContents) {
// split by comma and remove redundant spaces
String[] data = csvLine.split("\\s*,\\s*");
System.out.println(data[1]);// IndexOutOfBound
Character character = null;
String clazz = data[0].toLowerCase();// cannot use word "class" as a variable
if (clazz.startsWith("scenario"&& data.length == 1)) {
scenario = new Scenario();
scenario.setLegalCrossing(clazz.endsWith("green"));
continue;
} else if ("person".equals(clazz)&& data.length == 10) {
Profession professionEnum = Profession.valueOf(data[4].toUpperCase());
Gender genderEnum = Gender.valueOf(data[1].toUpperCase());
BodyType bodyTypeEnum =BodyType.valueOf(data[3].toUpperCase());
person = new Person(Integer.parseInt(data[2]), professionEnum ,genderEnum , bodyTypeEnum , Boolean.parseBoolean(data[5]));
person.setAsYou(Boolean.parseBoolean(data[6]));
} else if ("animal".equals(clazz)) {
animal = new Animal(Integer.parseInt(data[2]) , genderEnum , bodyTypeEnum, data[7]);
animal.setIsPet(Boolean.parseBoolean(data[8]));
}
} catch (someException e) {
e.printStackTrace();
}
I'm hoping to trim all Strings that are part of an object graph.
So I have an object graph like so
RootElement
- name (String)
- adjective (String)
- items ArrayOfItems
- getItems (List<Item>)
- get(i) (Item)
Item
- name (String)
- value (double)
- alias (String)
- references ArrayOfReferences
- getReferences (List<Reference>)
- get(i) (Reference)
Reference
- prop1 (String)
- prop2 (Integer)
- prop3 (String)
There is a get and set pair for every property of every class represented in this object graph. Ideally every field of type String would end up trimmed, including enumerating any child objects contained in collections. There are no cycles contained within the object graph.
Is there any java library that implements some sort of generic object graph visitor pattern or String\Reflection utility library that does this?
An external third party library that does this would also be fine, it does not have to be part of the standard java libraries.
No, there's no built-in traversal for something like this, and remember that Java Strings are immutable, so you can't actually trim in place--you have to trim and replace. Some objects may not permit modification of their String variables.
Below is the explanation of solution that I have built using Java Reflection API. I have posted the working code (with its url to github) below. This solution mainly uses:
Java Reflection API
Independent handling of Java Collections
Recursion
To start with, I have used Introspector to go over the readMethods of the Class omitting the methods defined for Object
for (PropertyDescriptor propertyDescriptor : Introspector
.getBeanInfo(c, Object.class).getPropertyDescriptors()) {
Method method = propertyDescriptor.getReadMethod();
Cases
If the current level of Property is of type String
If its an Object Array of Properties
If its a String array
If its a type of Java Collection class
Separate placement for Map with special conditions to process its keys and values
This utility uses the Java Reflection API to traverse through an object graph with disciplined syntax of getters and setters and trims all strings encountered within an Object graph recursively.
Code
This entire util class with the main test class (and custom data types/pojos) is here on my github
Usage:
myObj = (MyObject) SpaceUtil.trimReflective(myObj);
Util method:
public static Object trimReflective(Object object) throws Exception {
if (object == null)
return null;
Class<? extends Object> c = object.getClass();
try {
// Introspector usage to pick the getters conveniently thereby
// excluding the Object getters
for (PropertyDescriptor propertyDescriptor : Introspector
.getBeanInfo(c, Object.class).getPropertyDescriptors()) {
Method method = propertyDescriptor.getReadMethod();
String name = method.getName();
// If the current level of Property is of type String
if (method.getReturnType().equals(String.class)) {
String property = (String) method.invoke(object);
if (property != null) {
Method setter = c.getMethod("set" + name.substring(3),
new Class<?>[] { String.class });
if (setter != null)
// Setter to trim and set the trimmed String value
setter.invoke(object, property.trim());
}
}
// If an Object Array of Properties - added additional check to
// avoid getBytes returning a byte[] and process
if (method.getReturnType().isArray()
&& !method.getReturnType().isPrimitive()
&& !method.getReturnType().equals(String[].class)
&& !method.getReturnType().equals(byte[].class)) {
System.out.println(method.getReturnType());
// Type check for primitive arrays (would fail typecasting
// in case of int[], char[] etc)
if (method.invoke(object) instanceof Object[]) {
Object[] objectArray = (Object[]) method.invoke(object);
if (objectArray != null) {
for (Object obj : (Object[]) objectArray) {
// Recursively revisit with the current property
trimReflective(obj);
}
}
}
}
// If a String array
if (method.getReturnType().equals(String[].class)) {
String[] propertyArray = (String[]) method.invoke(object);
if (propertyArray != null) {
Method setter = c.getMethod("set" + name.substring(3),
new Class<?>[] { String[].class });
if (setter != null) {
String[] modifiedArray = new String[propertyArray.length];
for (int i = 0; i < propertyArray.length; i++)
if (propertyArray[i] != null)
modifiedArray[i] = propertyArray[i].trim();
// Explicit wrapping
setter.invoke(object,
new Object[] { modifiedArray });
}
}
}
// Collections start
if (Collection.class.isAssignableFrom(method.getReturnType())) {
Collection collectionProperty = (Collection) method
.invoke(object);
if (collectionProperty != null) {
for (int index = 0; index < collectionProperty.size(); index++) {
if (collectionProperty.toArray()[index] instanceof String) {
String element = (String) collectionProperty
.toArray()[index];
if (element != null) {
// Check if List was created with
// Arrays.asList (non-resizable Array)
if (collectionProperty instanceof List) {
((List) collectionProperty).set(index,
element.trim());
} else {
collectionProperty.remove(element);
collectionProperty.add(element.trim());
}
}
} else {
// Recursively revisit with the current property
trimReflective(collectionProperty.toArray()[index]);
}
}
}
}
// Separate placement for Map with special conditions to process
// keys and values
if (method.getReturnType().equals(Map.class)) {
Map mapProperty = (Map) method.invoke(object);
if (mapProperty != null) {
// Keys
for (int index = 0; index < mapProperty.keySet().size(); index++) {
if (mapProperty.keySet().toArray()[index] instanceof String) {
String element = (String) mapProperty.keySet()
.toArray()[index];
if (element != null) {
mapProperty.put(element.trim(),
mapProperty.get(element));
mapProperty.remove(element);
}
} else {
// Recursively revisit with the current property
trimReflective(mapProperty.get(index));
}
}
// Values
for (Map.Entry entry : (Set<Map.Entry>) mapProperty
.entrySet()) {
if (entry.getValue() instanceof String) {
String element = (String) entry.getValue();
if (element != null) {
entry.setValue(element.trim());
}
} else {
// Recursively revisit with the current property
trimReflective(entry.getValue());
}
}
}
} else {// Catch a custom data type as property and send through
// recursion
Object property = (Object) method.invoke(object);
if (property != null) {
trimReflective(property);
}
}
}
} catch (Exception e) {
throw new Exception("Strings cannot be trimmed because: ", e);
}
return object;
}
Test
I also have a test class in there which creates a relatively complex object. The test class has different scenarios that cover:
String properties
Properties as custom datatypes which in turn have String properties
Properties as custom datatypes which in turn have properties as custom datatypes which in turn have String properties
List of custom data types
Set of Strings
Array of custom data types
Array of Strings
Map of String and custom data type
Object Graph:
Test Object Code Snippet:
public static Music buildObj() {
Song song1 = new Song();
Song song2 = new Song();
Song song3 = new Song();
Artist artist1 = new Artist();
Artist artist2 = new Artist();
song1.setGenre("ROCK ");
song1.setSonnet("X ");
song1.setNotes("Y ");
song1.setCompostions(Arrays.asList(new String[] { "SOME X DATA ",
"SOME OTHER DATA X ", "SOME MORE DATA X ", " " }));
Set<String> instruments = new HashSet<String>();
instruments.add(" GUITAR ");
instruments.add(" SITAR ");
instruments.add(" DRUMS ");
instruments.add(" BASS ");
song1.setInstruments(instruments);
song2.setGenre("METAL ");
song2.setSonnet("A ");
song2.setNotes("B ");
song2.setCompostions(Arrays.asList(new String[] { "SOME Y DATA ",
" SOME OTHER DATA Y ",
" SOME MORE DATA Y ", " " }));
song3.setGenre("POP ");
song3.setSonnet("DONT ");
song3.setNotes("KNOW ");
song3.setCompostions(Arrays.asList(new String[] { "SOME Z DATA ",
" SOME OTHER DATA Z ",
" SOME MORE DATA Z ", " " }));
artist1.setSongList(Arrays.asList(new Song[] { song1, song3 }));
artist2.setSongList(Arrays.asList(new Song[] { song1, song2, song3 }));
Map<String, Person> artistMap = new HashMap<String, Person>();
Person tutor1 = new Person();
tutor1.setName("JOHN JACKSON DOE ");
artistMap.put(" Name ", tutor1);
Person coach1 = new Person();
coach1.setName("CARTER ");
artistMap.put("Coach ", coach1);
artist2.setTutor(artistMap);
music.setSongs(Arrays.asList(new Song[] { song1, song2, song3 }));
music.setArtists(Arrays.asList(new Artist[] { artist1, artist2 }));
music.setLanguages(new String[] { " ENGLISH ", "FRENCH ",
"HINDI " });
Person singer1 = new Person();
singer1.setName("DAVID ");
Person singer2 = new Person();
singer2.setName("JACOB ");
music.setSingers(new Person[] { singer1, singer2 });
Human man = new Human();
Person p = new Person();
p.setName(" JACK'S RAGING BULL ");
SomeGuy m = new SomeGuy();
m.setPerson(p);
man.setMan(m);
music.setHuman(man);
return music;
}
Outcome:
#######BEFORE#######
>>[>>DAVID ---<<, >>JACOB ---<<]---[ ENGLISH , FRENCH , HINDI ]---[>>ROCK ---X ---Y ---[SOME X DATA , SOME OTHER DATA X , SOME MORE DATA X , ]---[ SITAR , GUITAR , BASS , DRUMS ]<<, >>METAL ---A ---B ---[SOME Y DATA , SOME OTHER DATA Y , SOME MORE DATA Y , ]---<<, >>POP ---DONT ---KNOW ---[SOME Z DATA , SOME OTHER DATA Z , SOME MORE DATA Z , ]---<<]---[>>---[>>ROCK ---X ---Y ---[SOME X DATA , SOME OTHER DATA X , SOME MORE DATA X , ]---[ SITAR , GUITAR , BASS , DRUMS ]<<, >>POP ---DONT ---KNOW ---[SOME Z DATA , SOME OTHER DATA Z , SOME MORE DATA Z , ]---<<]<<, >>{Coach =>>CARTER ---<<, Name =>>JOHN JACKSON DOE ---<<}---[>>ROCK ---X ---Y ---[SOME X DATA , SOME OTHER DATA X , SOME MORE DATA X , ]---[ SITAR , GUITAR , BASS , DRUMS ]<<, >>METAL ---A ---B ---[SOME Y DATA , SOME OTHER DATA Y , SOME MORE DATA Y , ]---<<, >>POP ---DONT ---KNOW ---[SOME Z DATA , SOME OTHER DATA Z , SOME MORE DATA Z , ]---<<]<<]---=> JACK'S RAGING BULL <=<<
Number of spaces : 644
#######AFTER#######
>>[>>DAVID---<<, >>JACOB---<<]---[ENGLISH, FRENCH, HINDI]---[>>ROCK---X---Y---[SOME X DATA, SOME OTHER DATA X, SOME MORE DATA X, ]---[GUITAR, SITAR, DRUMS, BASS]<<, >>METAL---A---B---[SOME Y DATA, SOME OTHER DATA Y, SOME MORE DATA Y, ]---<<, >>POP---DONT---KNOW---[SOME Z DATA, SOME OTHER DATA Z, SOME MORE DATA Z, ]---<<]---[>>---[>>ROCK---X---Y---[SOME X DATA, SOME OTHER DATA X, SOME MORE DATA X, ]---[GUITAR, SITAR, DRUMS, BASS]<<, >>POP---DONT---KNOW---[SOME Z DATA, SOME OTHER DATA Z, SOME MORE DATA Z, ]---<<]<<, >>{Name=>>JOHN JACKSON DOE---<<, Coach=>>CARTER---<<}---[>>ROCK---X---Y---[SOME X DATA, SOME OTHER DATA X, SOME MORE DATA X, ]---[GUITAR, SITAR, DRUMS, BASS]<<, >>METAL---A---B---[SOME Y DATA, SOME OTHER DATA Y, SOME MORE DATA Y, ]---<<, >>POP---DONT---KNOW---[SOME Z DATA, SOME OTHER DATA Z, SOME MORE DATA Z, ]---<<]<<]---=>JACK'S RAGING BULL<=<<
Number of spaces : 111
There is a non-zero count of the number of spaces in the above trimmed output because I didn't make an effort to override toString of any collections (List, Set) or Map. There are certain improvements to the code I want to make but for your case the solution should work just fine.
Limitations (further improvements)
Cannot handle undisciplined syntax of properties (invalid getters/setters)
Cannot handle chained Collections: for example, List<List<Person>> - because of the exclusive support to disciplined getters/setters convention
No Guava collection library support
Building off #SwissArmyKnife I converted his simple String trimming function into an interface with a default method. So any object where you would like to use object.trim(), you just have to add "implements Trimmable".
Simple String trim interface: Trimmable.class
/**
* Utility interface that trims all String fields of the implementing class.
*/
public interface Trimmable {
/**
* Trim all Strings
*/
default void trim(){
for (Field field : this.getClass().getDeclaredFields()) {
try {
field.setAccessible(true);
Object value = field.get(this);
if (value != null){
if (value instanceof String){
String trimmed = (String) value;
field.set(this, trimmed.trim());
}
}
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
An object that we would like to be trimmable: Person.class (implements Trimmable interface)
public class Person implements Trimmable {
private String firstName;
private String lastName;
private int age;
// getters/setters omitted
}
Now you can use person.trim()
Person person = new Person();
person.setFirstName(" John ");
person.setLastName(" Doe");
person.setAge(30);
person.trim();
I made a simple method for trimming String values with Reflection API.
public Object trimStringValues(Object model){
for(Field field : model.getClass().getDeclaredFields()){
try{
field.setAccessible(true);
Object value = field.get(model);
String fieldName = field.getName();
if(value != null){
if(value instanceof String){
String trimmed = (String) value;
field.set(model, trimmed.trim());
}
}
}catch(Exception e){
e.printStackTrace();
}
}
}
I haven't bumped in to any problems with this one yet. I know its an old thread, but it might help somone whos is looking for something simple.
I have a method getFormattedValue(List<String> dataHeaders, List<String> data) that returns String value based contents of dataHeaders and data list. dataHeaders list can have 10 distinct values and based on value at particular index output string formation changes.
Below code was working fine tiil the time when dataHeaders contents are received in specific order , but lately this order is changing many atimes. As this input is received from other app/ system, i do not have control over order of elements. Hence i want to update my code so that it works correctly even after input order is altered.
If 1'st element of dataHeaders list is "OPERATION_NAME" then i need not take any action, but if "OPERATION_NAME" comes at 2'nd index in dataHeaders list then i need to do special formatting to output value. And so on....
My Pain is that i receive 10 dataHeaders. Please suggest me any good approach to handle this issue. I am posting my code below, suggestions are welcome.
import java.util.ArrayList;
import java.util.List;
public class ValueGenerator {
public String getFormattedValue(List<String> dataHeaders, List<String> data){
String formattedOutValue=null;
if(dataHeaders!=null && data!=null &&
dataHeaders.size() == data.size()){
if(dataHeaders.get(0).equals("OPERATION_NAME")){
formattedOutValue=data.get(0); // Add no spaces
}else if(dataHeaders.get(1).equals("OPERATION_NAME")){
formattedOutValue=data.get(1)+" "; // Add 4 blank spaces
}else if(dataHeaders.get(2).equals("OPERATION_NAME")){
formattedOutValue=data.get(2)+" "; // Add 6 blank spaces
}
}
//likewise i want to avoid redundant if - else if check
return formattedOutValue;
}
}
I assume that you want data.get(2) in the case of dataHeaders.get(2) and not data.get(1)
Basically you just need to find the index of the string OPERATION_NAME in dataHeaders and use it for data. The simplest way is to iterate over the list dataHeaders with an index and stop when you find it.
If you need to handle more strings then you could use a Map to map the strings you want to evaluate to their indices, this could look like this:
final static Map<Integer, String> formatByIndexMap;
static {
formatByIndexMap = new HashMap<>();
formatByIndexMap.put(0, "");
formatByIndexMap.put(1, " ");
formatByIndexMap.put(2, " ");
// and so on
formatByIndexMap.put(9, "----format for 10----");
}
public String getFormattedValue(List<String> dataHeaders, List<String> data){
String formattedOutValue = null;
if (dataHeaders != null && data != null &&
dataHeaders.size() == data.size()) {
Map<String, Integer> dhm = new HashMap<>();
for(int i = 0; i < dataHeaders.size(); i++) {
dhm.put(dataHeaders.get(i), i);
}
Integer operationNameIndex = dhm.get("OPERATION_NAME");
if(operationNameIndex != null) {
formattedOutValue = data.get(operationNameIndex.intValue()) +
formatByIndexMap.get(operationNameIndex);
}
}
return formattedOutValue;
}
The format map formatByIndexMap is defines as final static.
An for some basic testing:
#Test
public void getFormattedValue() {
List<String> data = Arrays.asList("operation", "foo", "bar");
List<String> dataHeaders;
String formated;
dataHeaders = Arrays.asList("OPERATION_NAME", "FOO_NAME", "BAR_NAME");
formated = getFormattedValue(dataHeaders, data);
Assert.assertEquals("operation", formated); // no spaces
dataHeaders = Arrays.asList("FOO_NAME", "OPERATION_NAME", "BAR_NAME");
formated = getFormattedValue(dataHeaders, data);
Assert.assertEquals("foo ", formated); // four spaces
dataHeaders = Arrays.asList("FOO_NAME", "BAR_NAME", "OPERATION_NAME");
formated = getFormattedValue(dataHeaders, data);
Assert.assertEquals("bar ", formated); // six spaces
dataHeaders = Arrays.asList("FOO_NAME", "BAR_NAME", "", "", "", "", "",
"", "", "OPERATION_NAME");
data = Arrays.asList("operation", "foo", "bar", "", "", "", "",
"", "", "tail");
formated = getFormattedValue(dataHeaders, data);
// ----format for 10----
Assert.assertEquals("tail----format for 10----", formated);
}
I have a csv dataset like this:
A, 10, USA
B,30, UK
C,4,IT
A,20,UK
B,10,USA
I want to read this csv lines and provide the following output:
A has ran 30 miles with average of 15.
B has ran 30 miles with average of 20.
C has ran 4 miles with average of 4.
I want to achieve this in Java. I have done this in C# by using Linq:
var readlines = File.ReadAllLines(filename);
var query = from lines in readlines
let data = lines.Split(',')
select new
{
Name = data[0],
Miles = data[1],
};
var values = query.GroupBy(x => new {x.Name}).Select(group => new { Person = group.Key, Events = group.Sum(g =>Convert.ToDouble(g.Miles)) ,Count = group.Count() });
I am looking to do this in Java, and I am not sure if I can do this without using any third party library or not? Any ideas?
So far, my code looks like this in Java:
CSVReader reader = new CSVReader(new FileReader(filename));
java.util.List<String[]> content = reader.readAll();
String[] row = null;
for(Object object:content)
{
row = (String[]) object;
String Name = row[0];
String Miles = row[1];
System.out.printf("%s has ran %s miles %n",Name,Miles);
}
reader.close();
}
I am looking for a nice way to get the total milage value for each name to calculate for the average.
As a C# developer, it is hard sometimes not to miss the features of linq. But as Farlan suggested you could do something like this:
CSVReader reader = new CSVReader(new FileReader(filename));
java.util.List<String[]> content = reader.readAll();
Map<String, Group> groups = new HashMap<>();
for(String[] row : content)
{
String Name = row[0];
String Miles = row[1];
System.out.printf("%s has ran %s miles %n", Name, Miles);
if (groups.containsKey(Name)){
groups.get(Name).Add(Double.valueOf(Miles));
} else {
Group g = new Group();
g.Add(Double.valueOf(Miles));
groups.put(Name, g);
}
}
reader.close();
for (String name : groups.keySet())
{
System.out.println(name + " ran " + groups.get(name).total() + " with avg of " + groups.get(name).average());
}
}
class Group {
private List<Double> miles;
public Group()
{
miles = new ArrayList<>();
}
public Double total(){
double sum = 0;
for (Double mile : miles)
{
sum += mile;
}
return sum;
}
public Double average(){
if (miles.size() == 0)
return 0d;
return total() / miles.size();
}
public void Add(Double m){
miles.add(m);
}
}
Use Java's BufferedReader class:
BufferedReader in = new BufferedReader(new FileReader("your.csv"));
String line;
while ( (line = in.readLine()) != null) {
String [] fields = line.split(",");
System.out.println(fields[0] + " has ran " + fields[1] + " miles with average " + fields[2]);
}
There are quite a few ways to do this, some long-winded approaches, some shorter. The issue is that Java can be very verbose for doing simple tasks, so the better approaches can be a bit uglier.
The example below shows you exactly how to achieve this, par the printing. Bear in mind however, it might not be the best approach but I feel its more of the easier ones to read and comprehend.
final File csvFile = new File("filename.csv");
final Scanner reader = new Scanner(csvFile);
final Map<String, Integer> info = new HashMap<>(); //Store the data
//Until there is are no more lines, continue
while (reader.hasNextLine()) {
final String[] data = reader.nextLine().split(","); // data[0] = A. [1] = 10. [2] = USA
final String alpha = data[0];
if (!info.containsKey(alpha)) {
info.put(alpha, Integer.parseInt(data[1]));
} else {
int miles = info.get(alpha);
info.put(alpha, miles + Integer.parseInt(data[1]));
}
}
reader.close();
The steps involved are simple:
Step 1 - Read the file.
By passing a File into the Scanner object, you set the target parsing to the File and not the console. Using the very neat hasNextLine() method, you can continually read each line until no more exist. Each line is then split by a comma, and stored in a String array for reference.
Step 2 - Associating the data.
As you want to cumulatively add the integers together, you need a way to associate already passed in letters with the numbers. A heavyweight but clean way of doing this is to use a HashMap. The Key which it takes is going to be a String, specifically A B or C. By taking advantage of the fact the Key is unique, we can use the O(1) containsKey(String) method to check if we've already read in the letter. If its new, add it to the HashMap and save the number with it. If however, the letter has been seen before, we find the old value, add it with the new one and overwrite the data inside the HashMap.
All you need to do now is print out the data. Feel free to take a different approach, but I hope this is a clear example of how you CAN do it in Java.
Maybe you could try this Java library: https://code.google.com/p/qood/
It handles data without any getter/setters, so it's more flexible than LINQ.
in your case, file "D:/input.csv" has 3 columns:
NAME,MILES,COUNTRY
A, 10, USA
B,30, UK
C,4,IT
A,20,UK
B,10,USA
the query code would be:
final QModel raw = QNew.modelCSV("D:/input.csv")
.debug(-1);//print out what read from CSV
raw.query()
.selectAs("OUTPUT",
"CONCAT(NAME,' has ran ',SUM(MILES),' miles with average of ',MEAN(MILES),'.')")
.groupBy("NAME")
.result().debug(-1)//print out the result
.to().fileCSV("D:/output.csv", "UTF-8");//write to another CSV file