How to get unique values ​​from ArrayList using Java 8?

Extracting unique values ​​from an ArrayList becomes easier and faster by leveraging Java 8’s functional programming features like the Stream API, streams, and lambda expressions. Using these features, you can extract different elements without tedious iteration or manual inspection; lambda expressions make this task easier by allowing you to write concise and readable code. Whether dealing with large data sets or simply eliminating duplicates, Java 8 provides powerful and elegant solutions to retrieve unique values ​​from ArrayList

Array list

Java's ArrayList class implements the List interface, providing functions similar to dynamic arrays for storing and operating collections of elements in adjustable arrays. When elements are added to or removed from an ArrayList array, its size is automatically adjusted, providing flexibility and convenience.

There are many methods to access, modify, add and delete elements in ArrayList. Elements can be accessed using the get() method and modified using the set() method; in addition, elements can be added at a specific position in the list using the add() method, and elements can be removed at a specific position using the remove() method, or at the end of the list. Add or remove elements

ArrayList<String> names = new ArrayList<>();

method

Java 8 provides several ways to find unique values ​​in an arrayList. Below are two strategies that are often used.

• Use Stream and distinct()

• Use hash set

Both methods provide an efficient way to extract unique values ​​from an ArrayList using Java 8 features, so just choose the method that best suits your requirements and coding style.

Use Stream and distinct()

First, convert the ArrayList to a stream by calling its stream() method; then use unique() on the stream to filter out duplicate values ​​so that only unique items are retained. In order to extract unique values ​​from the stream, the collect() method with an appropriate collector allows retrieving them.

For optimal use of distinct(), please ensure that the elements in the ArrayList have correctly overridden the equals() method to ensure their uniqueness, and correctly define themselves as distinct elements

algorithm

• Create an ArrayList and fill it with elements.

• Use the stream() method to convert ArrayList to a stream

• Apply the unique() method on a Stream to eliminate duplicate values ​​and keep only unique values.

• Convert the stream back to an ArrayList or other appropriate collection using the collect() method and an appropriate collector

• This new ArrayList will only contain unique values ​​from its source ArrayList.

program

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

public class UniqueValuesExample {
   public static void main(String[] args) {
      List<String> fruits = new ArrayList<>();
      fruits.add("Apple");
      fruits.add("Orange");
      fruits.add("Banana");
      fruits.add("Orange");
      fruits.add("Mango");
      fruits.add("Apple");

      List<String> uniqueFruits = fruits.stream()
         .distinct()
         .collect(Collectors.toList());

      System.out.println("Unique fruits: " + uniqueFruits);
   }
}

Output

Unique fruits: [Apple, Orange, Banana, Mango]

Use HashSet

Start the editor. Assemble the HashSet objects into a collection that holds unique elements, then iterate through each element in the ArrayList one by one to add it to the HashSet, noting any duplicate values ​​that occur. Since HashSet does not allow duplicate values ​​to exist, any duplicate data in the ArrayList will be automatically eliminated by HashSet

After iterating the ArrayList, creating a HashSet containing only the unique values ​​from the original list allows you to access those specific values ​​directly or convert back to an ArrayList for further access.

This method takes advantage of the inherent uniqueness constraint of HashSet to quickly retrieve unique values ​​from the ArrayList, providing a convenient solution in Java 8.

algorithm

• Create an ArrayList and fill it with elements.

• Create a HashSet object.

• Traverse each element in ArrayList

• Use the add() method to add each element to the HashSet

• HashSet will automatically eliminate duplicate values ​​because it only stores unique values.

• After traversing the ArrayList, the HashSet will contain only those unique values ​​in the original list.

• You can switch the HashSet back to an ArrayList if needed, or use it directly as an access tool to find unique values ​​within it

program

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class UniqueValuesExample {
   public static void main(String[] args) {
      List<String> animals = new ArrayList<>();
      animals.add("Lion");
      animals.add("Elephant");
      animals.add("Tiger");
      animals.add("Elephant");
      animals.add("Giraffe");
      animals.add("Lion");

      Set<String> uniqueAnimals = new HashSet<>(animals);

      System.out.println("Unique animals: " + uniqueAnimals);
   }
}

Output

Unique animals: [Elephant, Lion, Tiger, Giraffe]

in conclusion

In this tutorial, we saw how Java 8 provides an efficient and elegant solution to extract unique values ​​from an ArrayList. By leveraging its Stream API's unique() method and quickly eliminating duplicates from an ArrayList to get new unique items, and its functional programming capabilities for concise and readable code, developers can do it easily, quickly, and efficiently this task.

HashSet can also provide another efficient way to find unique values ​​by initializing it with an ArrayList; any duplicate elements are automatically eliminated, leaving only the unique entries within it.

Java 8’s flexibility and convenience in handling the task of extracting unique values ​​from an ArrayList is clearly evident from these methods; both of them leverage its Stream API or HashSet implementation for maximum productivity, helping developers achieve their goals easily.

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