java treemap

TreeMap类pollFirstEntry()方法 (TreeMap Class pollFirstEntry() method)

• pollFirstEntry() method is available in java.util package.

  pollFirstEntry()方法在java.util包中可用。

• pollFirstEntry() method is used to return and then remove the entry (key-value pair) linked with the lowest key element value that exists in this TreeMap.

  pollFirstEntry()方法用于返回，然后删除与此TreeMap中存在的最低键元素值链接的条目(键值对)。

• pollFirstEntry() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.

  pollFirstEntry()方法是一种非静态方法，只能通过类对象访问，如果尝试使用类名访问该方法，则会收到错误消息。

• pollFirstEntry() method does not throw an exception at the time of returning first entry.

  返回第一个条目时， pollFirstEntry()方法不会引发异常。

Syntax:

句法：

    public Map.Entry pollFirstEntry();

Parameter(s):

参数：

• It does not accept any parameter.

  它不接受任何参数。

Return value:

返回值：

The return type of the method is Map.Entry, it retrieves an entry with the lowest key element value when exists otherwise it returns null.

该方法的返回类型为Map.Entry ，如果存在，则检索具有最低键元素值的条目，否则返回null。

Example:

例：

// Java program to demonstrate the example 
// of Map.Entry pollFirstEntry () 
// method of TreeMap 
import java.util.*;
public class PollFirstEntryOfTreeMap {
public static void main(String[] args) {
// Instantiates TreeMap
TreeMap < Integer, String > tm = new TreeMap < Integer, String > ();
// By using put() method is
// to put the key-value pairs in
// treemap tm
tm.put(1, "C");
tm.put(4, "C++");
tm.put(3, "Java");
tm.put(2, "Php");
// Display TreeMap tm
System.out.println("tm: " + tm);
// By using pollFirstEntry() method is to
// return and remove the key-value pairs
// linked with the least key element value
// i.e. "1"
tm.pollFirstEntry();
// Display updated TreeMap tm
System.out.println("tm.pollFirstEntry(): " + tm);
}
}

Output

输出量

tm: {1=C, 2=Php, 3=Java, 4=C++}
tm.pollFirstEntry(): {2=Php, 3=Java, 4=C++}

翻译自: https://www.includehelp.com/java/treemap-pollfirstentry-method-with-example.aspx

java treemap