Hello! In this tutorial, we will learn about representing collections in Java. Collections are one of the important data structures in algorithm problem-solving. Therefore, understanding and being able to use them can greatly help in Java coding tests. In this post, I will explain a basic problem of representing a collection and its solution process in detail.
Problem: Create a Set without Duplicates
Given an array of integers, write a function that converts it to a Set and returns it as a list after removing duplicate elements.
Input
- Array:
[1, 2, 2, 3, 4, 4, 5]
Output
- List:
[1, 2, 3, 4, 5]
Problem-Solving Process
To solve this problem, it is important to first understand the definition of a Set. A Set is a data structure that does not allow duplicate values, and in Java, it can be implemented using HashSet. Below is a summary of the main processes to solve the problem.
1. Confirming the Need for a Set
To remove duplicate elements from the given array, we need to use a Set. Using a Set naturally handles duplicates and maintains the uniqueness of each element. For example, in the array [1, 2, 2, 3, 4, 4, 5], since 2 and 4 are duplicates, converting it to a Set results in [1, 2, 3, 4, 5].
2. Using HashSet in Java
To implement a Set in Java, we can use the HashSet class. HashSet is an implementation of a Set that uses a hash table internally, allowing elements to be added and searched with a time complexity of O(1).
3. Implementing the Function
Now, let’s implement the function needed to solve the given problem. Take a look at the following code.
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
public class SetExample {
public static List<Integer> uniqueElements(int[] arr) {
// Removing duplicates using HashSet
Set<Integer> set = new HashSet<>();
for (int num : arr) {
set.add(num);
}
// Converting the Set to a List and returning it
return set.stream().collect(Collectors.toList());
}
public static void main(String[] args) {
int[] inputArray = {1, 2, 2, 3, 4, 4, 5};
List<Integer> result = uniqueElements(inputArray);
System.out.println(result); // [1, 2, 3, 4, 5]
}
}
4. Explaining the Code
The code above defines a function called uniqueElements that takes an array of integers as a parameter. This function uses HashSet to remove duplicate elements and then collects all elements in the Set into a List to return.
5. Entire Code Result
The main method above defines a sample array, then calls the uniqueElements function and prints the result. When this program is executed, you can see the following result:
[1, 2, 3, 4, 5]Conclusion and Further Learning
In this tutorial, we learned how to use HashSet to represent collections in Java. Sets are very useful in various algorithm problems, so it is necessary to practice to use them well. Enhance your skills by solving various problems related to Sets.
Additionally, I recommend studying the characteristics of Sets and various methods. For example, try implementing various Set operations like intersection, union, etc., and understand their differences from other data structures in the Java Collection Framework.
This tutorial ends here. Next time, I will return with a more interesting topic! Thank you.