Develop Reference

Don't understand how accessing CSV file in processing 3 works. Need an explanation

I have created previously a CSV file with textedit called titanicLinearisedDataSet.csv. My goal is to access this file using processing 3 and check whether element in a column are equal to string value "Nil". I don't receive result whereas the csv file contains "Nil"s.
I have joint an image of the CSV file
(CSV_file_image.jpg).
Thanks for your help !
String [][] array;
void setup() {
String [] lines = loadStrings("titanicLinearisedDataSet.csv");
array = new String[lines.length][3];
int i = 0;
for(String line: lines){
String [] pieces = split(line,",");
if(pieces[3] == "Nil"){
println("It worked");
}
}

You should not use == to compare String values. You should use the equals() function instead:
if(pieces[3].equals("Nil")){
println("It worked");
}
From the reference:
To compare the contents of two Strings, use the equals() method, as in if (a.equals(b)), instead of if (a == b). A String is an Object, so comparing them with the == operator only compares whether both Strings are stored in the same memory location. Using the equals() method will ensure that the actual contents are compared.
Also watch your curly brackets. The code you posted seems to be missing one.
If that doesn't work, try to get into the habit of debugging your code. For example, try printing out the values of pieces and pieces[3] to see exactly what's going on.

How do i declare custom generated strings inside a while loop?

What I'm trying to do is to declare a certain amount of strings according to the amount of tokens a scanner scans in a single input, then have these strings equal the next input. This is what I'm trying:
int numberOfTokens = 0;
boolean mainLoop = true;
Scanner input = new Scanner(System.in);
while(mainLoop == true)
{
while(input.hasNext())
{
String int(+ numberOfTokens) = input.next(); (this doesn't work)
numberOfTokens += 1;
}
}
I hope I made it clear of what I am trying to do. I tried using String arrays, but they won't work for what i'm trying to do.
Thanks.

You can do:
String[] myStringArray = new String[abc];
where abc is an integer you get from user
and then
myStringArray[index] = input.next();
and index must be a valid number between 0 and abc

If you don't know in advance how many strings you will need to store then an array is a poor choice of data structure, at least during the input phase. Use a List instead -- these keep the elements in order, yet expand as needed to accommodate new elements. They are convenient to work with overall, but if you ultimately must get the strings in array form (e.g. because some external API requires that form) then it is easy to obtain the corresponding array.
For example:
List<String> tokens = new ArrayList<>();
while (input.hasNext()) {
tokens.add(input.next());
// a List keeps track of its own length
}
If you later wanted the array then you could do
String[] tokenArray = tokens.toArray(new String[0]);
The number of tokens recorded in the List is available at any time as tokens.size(), or after you convert to an array, as tokenArray.length.
In any event, you cannot create new variables at runtime in Java.

Instead of string variables, you should declare one variable like this before the while loop.
List<String> tokens = new ArrayList<>();
while (input.hasNext()) {
tokens.add(input.next());
}
You can then operate on the tokens, like this:
int n = tokens.size();
for (String token : tokens) {
System.out.println(token);
}

convert String to arraylist of integers using wrapper class

Im trying to write a program that takes a string of user inputs such as (5,6,7,8) and converts it to an arrayList of integers e.g. {5,6,7,8}. I'm having trouble figuring out my for loop. Any help would be awesome.
String userString = "";
ArrayList<Integer> userInts = new ArrayList<Integer>();
System.out.println("Enter integers seperated by commas.");
userString = in.nextLine();
for (int i = 0; i < userString.length(); i++) {
userInts.add(new Integer(in.nextInt()));
}

If your list consists of single-digit numbers, your approach could work, except you need to figure out how many digits there are in the string before allocating the result array.
If you are looking to process numbers with multiple digits, use String.split on the comma first. This would tell you how many numbers you need to allocate. After than go through the array of strings, and parse each number using Integer.parseInt method.
Note: I am intentionally not showing any code so that you wouldn't miss any fun coding this independently. It looks like you've got enough knowledge to complete this assignment by reading through the documentation.

Lets look at the lines:
String userString = ""
int[] userInt = new int[userString.length()];
At this point in time userString.length() = 0 since it doesnt contain anything so this is the same as writing int[] userInt = new int[0] your instantiating an array that cant hold anything.
Also this is an array not an arrayList. An arrayList would look like
ArrayList<Integer> myList = new ArrayList()<Integer>;

I'm assuming the in is for a Scanner.
I don't see a condition to stop. I'll assume you want to keep doing this as long as you are happy.
List<Integer> arr = new ArrayList<Integer>();
while(in.hasNext())
arr.add(in.nextInt());
And, say you know that you will get 10 numbers..
int count = 10;
while(count-- > 0)
arr.add(in.nextInt());

Might I suggest a different input format? The first line of input will consist of an integer N. The next line contains N space separated integers.
5
3 20 602 3 1
The code for accepting this input in trivial, and you can use java.util.Scanner#nextInt() method to ensure you only read valid integer values.
This approach has the added benefit of validate the input as it is entered, rather than accepting a String and having to validate and parse it. The String approach presents so many edge cases which need to be handled.

Workaround for declaring array in an if condition

I have a problem with this part of the code where I want to be able to declare an array and the size of which should be the corresponding no of splits in the string.
Or do I need to count the no of commas in the string and allocate size accordingly or is there a better solution.
String MapPath2[];
if(type.equals("comparative"))
MapPath2[]=args[1].split(",");
I haven't had a chance to code in java in the recent past. Please spare me if it is a silly question and guide me as a noob. Appreciate your help.

You don't need to declare the size, what you have is fine if you remove the extra []:
String MapPath2[];
if(type.equals("comparative"))
MapPath2=args[1].split(",");
The array split gives back to you has the appropriate size. If you need to know the resulting size, use MapPath2.length (after assigning it).
You'd probably want to do something in the else as well, so that MapPath2 has a definite value either way:
String MapPath2[];
if(type.equals("comparative"))
MapPath2=args[1].split(",");
else
MapPath2=null;
or more concisely:
String MapPath2[];
MapPath2 = type.equals("comparative") ? args[1].split(",") : null;
(Instead of the nulls there, if having an empty array is preferred for subsequent logic as is sometimes handy, replace null with new String[0] above and below. Other times, it's more handy to have the null as a "no data" flag.)
Side note: There are some overwhelmingly common code style conventions in the Java world that you would be best advised to use in your code:
Variable names should start with a lower case letter, so as not to be confused with class names.
The [] should go with the type name rather than the variable name.
Always use {} even when the body of an if or else is only one line.
Put spaces around operators and keywords for ease of reading.
Applying those:
String[] mapPath2;
if (type.equals("comparative")) {
mapPath2 = args[1].split(",");
}
else {
mapPath2 = null;
}
Many people also put the else on the same line as the }, so:
String[] mapPath2;
if (type.equals("comparative")) {
mapPath2 = args[1].split(",");
} else {
mapPath2 = null;
}
Or again, more concisely:
String[] mapPath2;
mapPath2 = type.equals("comparative") ? args[1].split(",") : null;

You can use List instead of Array if you don't know what size it needs be.
Then you can use
List<String> list = new ArrayList<>();
if(type.equals("comparative")){
Collections.addAll(list, args[1].split(","));
}

Checking the end of a string in Java multiple times?

So in Java, I know that str.endsWith(suffix) tests if str ends with something. Let's say I have a text with the line "You are old" in it. How would I take the "old" and set it as a variable so I can print it out in the console?
I know I could do:
if(str.endsWith("old")){
String age = "old";
}
But then I'm going to have more options, so then I'd have to do:
if(str.endsWith("option1")){
String age = "option1";
}
if(str.endsWith("option2")){
String age = "option2";
}
...
Is there a more efficient and less verbose way to check the end of strings over writing many, possibly hundreds, of if statements
Format:
setting: option
setting2: option2
setting3: option3 ...
Regardless of what "option" is, I want to set it to a variable.

If you are working with sentences and you want to get the word, do
String word = str.substring(str.lastIndexOf(" "));
You may need a +1 after the lastIndexOf() to leave the space out.
Is that what you are looking for?

Open your file and read the line with the readLine() method. Then to get the last word of the string you can do as it is suggested here

You mean like:
String phrase = "old";
if(str.endsWith(old)){

Is this what you're looking for?
List<String> suffixes = new ArrayList<String>();
suffixes.add("old");
suffixes.add("young");
for(String s: suffixes)
{
if (str.endsWith(s))
{
String age = s;
// .... more of your code here...
}
}

If you're worried about repeating very similar code, the answer is always (99%) to create a function,
So in your case, you could do the following:
public void myNewFunction(String this, String that){
if(this.endsWith(that)){
String this = that;
}
}
...
String str = "age: old";
myNewFunction(str, "old"); //Will change str
myNewFunction(str, "new"); //Will NOT change str
And if that is too much, you can create a class which will do all of this for you. Inside the class, you can keep track of a list of keywords. Then, create a method which will compare a given word with each keyword. That way, you can call the same function on a number of strings, with no additional parameters.

You could use this Java code to solve your problem:
String suffix = "old";
if(str.endsWith(suffix)) {
System.out.println(suffix);
}