How to Split a List into Sublists Using Null Values as Separators in Java?

How can I split a list into sublists using null elements as separators in Java?

List<String> list = Arrays.asList("a", "b", null, "c", null, "d", "e");

To split a list into separate sublists using null as a separator in Java 8, you can use the Stream API combined with a custom collector. This approach will help you break down the original list into smaller lists while ignoring the null elements themselves.

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class SplitList {  
    public static void main(String[] args) {  
        List<String> list = Arrays.asList("a", "b", null, "c", null, "d", "e");  
        List<List<String>> sublists = splitList(list);  
        System.out.println(sublists);  
    }

    public static List<List<String>> splitList(List<String> list) {  
        List<List<String>> result = new ArrayList<>();  
        List<String> currentList = new ArrayList<>();  
        for (String item : list) {  
            if (item == null) {  
                if (!currentList.isEmpty()) {  
                    result.add(new ArrayList<>(currentList));  
                    currentList.clear();  
                }  
            } else {  
                currentList.add(item);  
            }  
        }
        if (!currentList.isEmpty()) {  
            result.add(currentList);  
        }
        return result;  
    }
}

Causes

• Using partitioningBy collects elements not based on custom criteria, but rather two categories which may not suit this need.
• Not using the appropriate stream and collector operations can lead to complexity and inefficiency.

Solutions

• Create a custom collector to accumulate items until a null is encountered, at which point you start a new sublist.
• Use Stream operations such as filter to manage null check and grouping.

Mistake: Using `Collectors.partitioningBy` incorrectly.

Solution: This method is not suitable for splitting the list by a null value. Instead, use custom logic with a simple for-loop.

Mistake: Failing to check for null values in the input list.

Solution: Always ensure to validate your list before processing to prevent NullPointerExceptions.