I know how to use an ArrayList as an object like so:
ArrayList<Integer> numbers = new ArrayList<>();
However, as part of an assignment, I'm supposed to fill out the provided method:
private static ArrayList<Token> parse(String s) { }
How am I supposed to work with the ArrayList (which I'm guessing is a parameter) in this case?
The ArrayList is the return value from the parse method. The only parameter is a String which you need to break up into tokens, place each token in the ArrayList and then return the list.
How you break up the list is specific to its initial format which you haven't mentioned. The example below shows how the method might look if the String was comma separated:
private static ArrayList<Token> parse(String s) {
String[] tokens = s.split(",");
return Arrays.asList(tokens);
}
See the API docs for split asList:
https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String,%20int)
https://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#asList(T...)
You can use java.util.Arrays for this
public List<String> parse(String s) {
return Arrays.asList(s.split(" "));
}
If you want to return List of Token and It your custom class then you have to make for loop like this
public List<Token> parse(String s) {
List<Token> tokenList = new ArrayList<>();
String[] strings = s.split(" ");
int length = strings.length;
for (int i = 0; i < length; i++) {
tokenList.add(new Token(strings[i]));
}
return tokenList;
}
If you want to convert a string into a ArrayList try this:
public ArrayList<Character> convertStringToArraylist(String str) {
ArrayList<Character> charList = new ArrayList<Character>();
for(int i = 0; i<str.length();i++){
charList.add(str.charAt(i));
}
return charList;
}
Or if you need to split a string and on basis of some delimiter (example ','), then use
List<String> myList = new ArrayList<String>(Arrays.asList(s.split(",")));
return myList;
sinto tokens, and then store each token in theArrayListwhich you then return to the caller.