A stream is a sequence of objects that supports various methods which can be pipelined to produce the desired result. Slice of a Stream means a stream of elements that exists in a specified limit, from the original stream.
Examples:
Input: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20] Output: [15, 16, 17, 18, 19] Explanation: The output contains a slice of the stream from index 4 to 8. Input: [1, 2, 3, 4, 5, 6, 7, 8, 9] Output: [2, 3, 4] Explanation: The output contains a slice of the stream from index 1 to 3.Below are the methods to remove nulls from a List in Java:
- Using skip() and limit(): Stream API in Java provides skip() method which is used to discard the other non-required elements from the stream. It also provides limit() function which is applied to fetch the new stream with the specified index as limit, in the encountered order.
Algorithm:
- Get the Stream to be sliced.
- Get the From and To index to be sliced from Stream as StartIndex and EndIndex
- Call skip() method to specify the number of elements to be skipped before the starting index as skip(startIndex)
- Call limit() method to specify the number of elements, from the stream, that should be limited as limit(endIndex - startIndex + 1)
- Return the Sliced Stream
Java // Java program to get slice of a stream using // Stream skip() and limit() import java.util.*; import java.util.stream.Stream; class GFG { // Generic function to get Slice of a // Stream from startIndex to endIndex public static <T> Stream<T> getSliceOfStream(Stream<T> stream, int startIndex, int endIndex) { return stream // specify the number of elements to skip .skip(startIndex) // specify the no. of elements the stream // that should be limited .limit(endIndex - startIndex + 1); } public static void main(String[] args) { // Create a new List with values 11 - 20 List<Integer> list = new ArrayList<>(); for (int i = 11; i <= 20; i++) list.add(i); // Create stream from list Stream<Integer> intStream = list.stream(); // Print the stream System.out.println("List: " + list); // Get Slice of Stream // containing of elements from the 4th index to 8th Stream<Integer> sliceOfIntStream = getSliceOfStream(intStream, 4, 8); // Print the slice System.out.println("\nSlice of Stream:"); sliceOfIntStream.forEach(System.out::println); } }
Output:List: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20] Slice of Stream: 15 16 17 18 19
- Using Collectors along with skip() and limit(): In this method, the Stream is converted to List and then a function of a collector to get sub-list of desired elements is used and the sub-list id converted back to a stream using stream.collect(Collectors.collectingAndThen()).
Algorithm:
- Get the Stream to be sliced.
- Get the From and To index to be sliced from Stream as StartIndex and EndIndex
- Using Collectors.collectingAndThen,
- Convert the Stream to List using Collectors.toList()
- Obtain the Stream from the List as list.stream()
- Call skip() method to specify the number of elements to be skipped before the starting index as skip(startIndex)
- Call limit() method to specify the number of elements, from the stream, that should be limited as limit(endIndex - startIndex + 1)
- Collect the sliced list stream using stream.collect()
- Return the Sliced Stream
Java // Java program to get slice of a stream using // Collection skip() and limit() import java.util.*; import java.util.stream.*; class GFG { // Generic function to get Slice of a // Stream from startIndex to endIndex public static <T> Stream<T> getSliceOfStream(Stream<T> stream, int startIndex, int endIndex) { return stream.collect(Collectors.collectingAndThen( // 1st argument // Convert the stream to list Collectors.toList(), // 2nd argument list -> list.stream() // specify the number of elements to skip .skip(startIndex) // specify the no. of elements the stream // that should be limited .limit(endIndex - startIndex + 1))); } public static void main(String[] args) { // Create a new List with values 11 - 20 List<Integer> list = new ArrayList<>(); for (int i = 11; i <= 20; i++) list.add(i); // Create stream from list Stream<Integer> intStream = list.stream(); // Print the stream System.out.println("List: " + list); // Get Slice of Stream // containing of elements from the 4th index to 8th Stream<Integer> sliceOfIntStream = getSliceOfStream(intStream, 4, 8); // Print the slice System.out.println("\nSlice of Stream:"); sliceOfIntStream.forEach(System.out::println); } }
Output:List: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20] Slice of Stream: 15 16 17 18 19
- Fetching a SubList: This method involves converting a Stream into a List. Now this list is used to fetch a required subList from it between the specified index. And finally, this subList is converted back to Stream.
Algorithm:
- Get the Stream to be sliced.
- Get the From and To index to be sliced from Stream as StartIndex and EndIndex
- Convert the Stream to List using Collectors.toList() and then collect it using stream.collect()
- Fetch the subList from the collected List with the startIndex and endIndex+1 as the limit using subList(startIndex, endIndex + 1)
- Convert the subList back to stream using stream()
- Return the Sliced Stream
Java // Java program to get slice of a stream by // fetching a sublist import java.util.*; import java.util.stream.*; class GFG { // Generic function to get Slice of a // Stream from startIndex to endIndex public static <T> Stream<T> getSliceOfStream(Stream<T> stream, int startIndex, int endIndex) { return stream // Convert the stream to list .collect(Collectors.toList()) // Fetch the subList between the specified index .subList(startIndex, endIndex + 1) // Convert the subList to stream .stream(); } public static void main(String[] args) { // Create a new List with values 11 - 20 List<Integer> list = new ArrayList<>(); for (int i = 11; i <= 20; i++) list.add(i); // Create stream from list Stream<Integer> intStream = list.stream(); // Print the stream System.out.println("List: " + list); // Get Slice of Stream // containing of elements from the 4th index to 8th Stream<Integer> sliceOfIntStream = getSliceOfStream(intStream, 4, 8); // Print the slice System.out.println("\nSlice of Stream:"); sliceOfIntStream.forEach(System.out::println); } }
Output:
List: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20] Slice of Stream: 15 16 17 18 19