Convert arraylist <String> to arraylist <integer> and check on which index is every word-CodePudding

i tried to write a code which convert array list to and return on which index is string given as parameter,

public class List {
public static void main(String[] List) {
    List<String> words = new ArrayList<>();
    words.addAll(Arrays.asList("house", "bike","dog","house","house"));
    System.out.println(getIntegerArray(words,house));


 public static List<Integer> getIntegerArray(List<String> words, String word) {
        List<Integer> numbers = new ArrayList<>();
        for (int i = 0; i < numbers.size() ; i  ) {

        }

And my goal is that output is arraylist>Integer>: [ 0,3,4]

First of all i want to check how many words contains arraylist 'words' so i will use loop for, after i check all of the elements and know how many there are i want to convert into Intager array list and output index of String word

CodePudding user response：

You can do it just by checking if the string passed to the method is contained in the list and adding the number to the List numbers.

Here an example of the method getIntegerArray:

public static List<Integer> getIntegerArray(List<String> words, String word) {
    List<Integer> numbers = new ArrayList<>();

    for (int i=0; i < words.size() ; i  ) {
        if (word.equals(words.get(i)))
            numbers.add(i);
    }
    return numbers;
}

PS: in System.out.println(getIntegerArray(words, house)); you are passing a variable house which is not declared. Probably you wanted to write "house".

CodePudding user response：

You should not worry about the size of numbers list, just add appropriate indexes as needed:

public static List<Integer> getIntegerArray(List<String> words, String word) {
    List<Integer> numbers = new ArrayList<>();
    for (int i = 0, n = words.size(); i < n; i  ) {
        if (Objects.equals(word, words.get(i)))
            numbers.add(i);
    }
    return numbers;
}

Or use Stream API to get the list of indexes:

public static List<Integer> getIntegerArray(List<String> words, String word) {
    return IntStream.range(0, words.size())
        .filter(i -> Objects.equals(word, words.get(i)))
        .boxed()
        .collect(Collectors.toList());
}