Java 中的 TreeSet pollLast()方法，示例

原文:https://www . geesforgeks . org/treeset-poll last-method-in-Java-with-example/

Java . util . concurrent . treeset的 pollLast() 方法是 Java 中的一个内置函数，它返回检索并移除最后一个(最高的)元素，如果这个集合为空，则返回 null。

语法:

public E pollLast()

返回值:函数返回检索并删除最后一个(最高的)元素，如果该集合为空，则返回 null。

下面的程序说明了 TreeSet.pollLast()方法:

程序 1:

// Java program to demonstrate pollLast()
// method of TreeSet

import java.util.*;

class TreeSetpollLastExample1 {
    public static void main(String[] args)
    {
        // Creating a set object
        TreeSet<Integer> set
            = new TreeSet<Integer>();

        // Adding elements to this set
        for (int i = 10; i <= 50; i += 10)
            set.add(i);

        // Printing the content of the set
        System.out.println("Contents of the set: " + set);

        // Retrieving and removing Last element of the set
        System.out.println("The Last element of the set: "
                           + set.pollLast());

        // Printing the content of the set after pollLast()
        System.out.println("Contents of the set after pollLast: "
                           + set);
    }
}

Output:

Contents of the set: [10, 20, 30, 40, 50]
The Last element of the set: 50
Contents of the set after pollLast: [10, 20, 30, 40]

程序 2:

// Java program to demonstrate pollLast()
// method of TreeSet

import java.util.*;

class TreeSetpollLastExample2 {
    public static void main(String[] args)
    {
        // Creating a set object
        TreeSet<Integer> set
            = new TreeSet<Integer>();

        // Printing the content of the set
        System.out.println("Contents of the set: "
                           + set);

        // Retrieving and removing Last element of the set
        System.out.println("The Last element of the set: "
                           + set.pollLast());
    }
}

Output:

Contents of the set: []
The Last element of the set: null

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