How to use HashSet.add() method to add elements to a collection in Java?

It is very simple to add elements to a collection using the HashSet.add() method in Java. Let’s introduce it in detail below.

HashSet is a collection class in Java. It inherits from the AbstractSet class and implements the Set interface. The characteristics of HashSet are unordered and non-repeating, and the underlying implementation is based on a hash table.

When using the HashSet.add() method to add elements, you need to pay attention to the following points:

1. HashSet can only store elements of object type, not elements of basic data types. . If you need to store elements of basic data types, you can use the corresponding packaging class to encapsulate them.
2. The elements in HashSet are unordered, and when adding elements, they will not be arranged in the order they are added.
3. The elements in the HashSet are not repeated. If you try to add an existing element, it will be ignored.

The following is a simple sample code that demonstrates how to use the HashSet.add() method to add elements to a collection:

import java.util.HashSet;

public class HashSetDemo {

    public static void main(String[] args) {
      
        HashSet<String> myHashSet = new HashSet<>();

        // 添加元素
        myHashSet.add("Apple");
        myHashSet.add("Banana");
        myHashSet.add("Kiwi");
        myHashSet.add("Orange");
        myHashSet.add("Grape");

        // 输出HashSet中的元素
        System.out.println("HashSet中的元素：" + myHashSet);

        // 尝试添加重复元素
        myHashSet.add("Apple");

        // 输出HashSet中的元素
        System.out.println("尝试添加重复元素后，HashSet中的元素：" + myHashSet);
    }
}

Run the above code, the output results are as follows:

HashSet中的元素：[Grape, Kiwi, Orange, Banana, Apple]
尝试添加重复元素后，HashSet中的元素：[Grape, Kiwi, Orange, Banana, Apple]

You can see that the elements in the HashSet are unordered and will be ignored when adding duplicate elements.

Through the above examples, I believe everyone already understands how to use the HashSet.add() method to add elements to a collection. In practical applications, different collection classes can be selected to store data according to specific needs for more efficient and convenient operations.

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