Java - iterate over List and remove indicated items
In this article, we would like to show you how to iterate over List and remove indicated items in Java.
Note:
By iterating and deleting, we change the structure of the list. After deleting an element, loop iterators get lost, that's why the API was issued.
In this example, we use an iterator to remove indicated items from the letters ArrayList.
xxxxxxxxxximport java.util.*;public class Example { public static void main(String[] args) { List<String> letters = new ArrayList<>(); letters.add("A"); letters.add("B"); letters.add("A"); letters.add("C"); Iterator<String> iterator = letters.iterator(); while (iterator.hasNext()) { String element = iterator.next(); if (element.equals("A")) { iterator.remove(); } } System.out.println(letters); }}Output:
xxxxxxxxxx[B, C]In this example, we use Java 8 removeIf() method to remove indicated elements from the letters ArrayList.
xxxxxxxxxximport java.util.*;public class Example { public static void main(String[] args) { List<String> letters = new ArrayList<>(); letters.add("A"); letters.add("B"); letters.add("A"); letters.add("C"); letters.removeIf(element -> element.equals("A")); System.out.println(letters); }}Output:
xxxxxxxxxx[B, C]In this example, we collect indicated elements in the new ArrayList, then we use removeAll() method that removes all the collected elements from the original ArrayList.
xxxxxxxxxximport java.util.*;public class Example { public static void main(String[] args) { List<String> letters = new ArrayList<>(); letters.add("A"); letters.add("B"); letters.add("A"); letters.add("C"); String letterToRemove = "A"; List<String> lettersToRemove = new ArrayList<>(); // find letters to remove for (String letter : letters) { if (letter.equals(letterToRemove)) { lettersToRemove.add(letter); } } // remove letters letters.removeAll(lettersToRemove); System.out.println(letters); }}Output:
xxxxxxxxxx[B, C]In this example, we create an instance of a stream from the letters ArrayList, filter each element and collect the result in the new filteredLetters.
xxxxxxxxxximport java.util.*;import java.util.stream.Collectors;public class Example { public static void main(String[] args) { List<String> letters = new ArrayList<>(); letters.add("A"); letters.add("B"); letters.add("A"); letters.add("C"); List<String> filteredLetters = letters .stream() .filter(element -> !element.equals("A")) .collect(Collectors.toList()); System.out.println(filteredLetters); }}Output:
xxxxxxxxxx[B, C]In this example, we remove all items from the letters ArrayList using reversed for loop.
xxxxxxxxxximport java.util.*;public class Example { public static void main(String[] args) { List<String> letters = new ArrayList<>(); letters.add("A"); letters.add("B"); letters.add("C"); for (int i = letters.size(); i-- > 0; ) { letters.remove(i); } System.out.println(letters); }}Output:
xxxxxxxxxx[]Note:
This solution is inefficient and not recommended.
