An implementation of obtaining data precursor and successor elements in a Java collection

Updated: May 01, 2024 08:37:00 Author: Long Da.

When using consistent hash, how to find a hash corresponding to the adjacent node, you can use the precursor and successor elements of the collection to obtain data, so this article introduces the implementation of the Java collection to obtain data precursor and successor elements, there are relevant code examples for everyone to refer to, need friends can refer to

catalogue

Usage scenario

When using consistent hash, how to find the adjacent node corresponding to a hash value can be implemented using the predecessor and successor elements of the collection to obtain data.

1. NavigableSet and NavigableMap

Features:
- The NavigableSet and NavigableMap interfaces provide rich methods to get the precursor and successor elements of a given element.
- higher(E e)Method returns the smallest element larger than the given element, or if no such element existsnull.
- lower(E e)Method returns the largest element smaller than the given element, or if no such element existsnull.
- ceiling(E e)Method returns the smallest element greater than or equal to the given element, or if no such element existsnull.
- floor(E e)Method returns the largest element that is less than or equal to the given element, or if no such element existsnull.
Implementation class:
- TreeSet and TreeMap are concrete implementations of NavigableSet and NavigableMap, which are both ordered sets.

2. ListIterator

peculiarity:
- Collections that implement the List interface, such as ArrayList or LinkedList, can be traversed using ListIterator iterators.
- The ListIterator provides itnext() 和 previous()Method to get the next and previous elements, respectively.

3. ConcurrentSkipListSet and ConcurrentSkipListMap

peculiarity:
- These two classes are thread-safe implementations of NavigableSet and NavigableMap.
- They provide the same precursor and successor methods as TreeSet and TreeMap and are suitable for concurrent environments.

4. Display columns

1. Use NavigableSet (TreeSet example)

import java.util.NavigableSet; import java.util.TreeSet; public class NavigableSetExample { public static void main(String[] args) { NavigableSet<Integer> set = new TreeSet<>();  set.add(1); set.add(3); set.add(5); set.add(7); Integer higher = set.higher(5); // Gets the successor element of the given element. Integer higher = set.higher(5); Integer lower = set.lower(5); // Return 7 // Gets the precursor element of the given element. Integer lower = set.lower(5); // Returns 3 System.out.println("Higher than 5: "+ higher); System.out.println("Lower than 5: " + lower); }}

import java.util.NavigableSet; import java.util.TreeSet; public class CeilingExample { public static void main(String[] args) { NavigableSet<Integer> set = new TreeSet<>(); set.add(1); set.add(3); set.add(5); set.add(7); Integer ceiling = set.ceiling(5); // Gets the smallest element greater than or equal to the given element. Integer ceiling = set.ceiling(5); // Returns 5 System.out.println("Ceiling of 5: "+ ceiling); }}

In this example, when calling set.ceiling(5); When, 5 will be returned. This is because 5 already exists in the set, so by the definition of the ceiling(E e) method, it will return the smallest element greater than or equal to the given element, in this case, 5 itself.

Sum up

In Java, if you need to get the next or previous data of a piece of data, you can use collections that implement NavigableSet or NavigableMap interfaces, such as TreeSet and TreeMap. Or its thread-safe versions ConcurrentSkipListSet and ConcurrentSkipListMap. For collections that implement the List interface, the preceding and following elements can be retrieved through the ListIterator. Choosing the right collection depends on the type of data, the sorting needs of the collection, and whether thread safety is required.

These are the details of the implementation of obtaining data precursor and successor elements in Java collections. For more information about obtaining data elements in Java collections, please pay attention to other related articles in Script House!

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