Use the first() method of the TreeSet class to get the first element in the tree collection

Use the first() method of the TreeSet class to get the first element in the tree collection

The TreeSet class is a collection class that uses a tree structure to store elements. It sorts the elements according to their natural order and does not Identical elements are allowed. In TreeSet, we can use the first() method to get the first element in the set. This article will introduce the usage of the first() method of the TreeSet class and give sample code.

First, we need to import the TreeSet class in the java.util package:

import java.util.TreeSet;

Next, we can create a TreeSet object and add some elements to it:

TreeSet<Integer> treeSet = new TreeSet<>();
treeSet.add(5);
treeSet.add(2);
treeSet.add(8);
treeSet.add(1);

In the above example code, we created a TreeSet object that stores an integer type and added four elements to it.

Then, we can use the first() method to get the first element in the collection:

int firstElement = treeSet.first();

In the above sample code, we get the treeSet collection by calling the first() method and stores it in an integer variable firstElement.

Finally, we can print out the value of the first element:

System.out.println("第一个元素是：" + firstElement);

Run the above code, we will get the following output:

第一个元素是：1

From the output result, you can It can be seen that the first() method returns the first element in the tree collection, which is the smallest element. In this example, the smallest element in the collection is 1, so the value returned by the first() method is 1.

It should be noted that before calling the first() method, we need to ensure that there is at least one element in the collection. Otherwise, if the collection is empty, calling the first() method will throw a NoSuchElementException exception.

To summarize, you can easily get the first element in the collection using the first() method of the TreeSet class. When using this method, we need to ensure that there is at least one element in the collection. I hope this article will help you understand and use the first() method of the TreeSet class.

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