java treemap

TreeMap类的firstEntry()方法 (TreeMap Class firstEntry() method)

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

  firstEntry()方法在java.util包中可用。

• firstEntry() method is used to retrieve the key-value pairs linked with the lowest value key element that exists in this TreeMap.

  firstEntry()方法用于检索与此TreeMap中存在的最低值键元素链接的键值对。

• firstEntry() 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.

  firstEntry()方法是一个非静态方法，只能通过类对象访问，如果尝试使用类名称访问该方法，则会收到错误消息。

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

  firstEntry()方法在返回条目时不会引发异常。

Syntax:

句法：

    public Map.Entry firstEntry();

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 key-value entry with the lowest key element exists otherwise it returns null when this TreeMap is "blank".

该方法的返回类型为Map.Entry ，它检索存在最低键元素的键值条目，否则当此TreeMap为“空白”时返回null。

Example:

例：

// Java program to demonstrate the example 
// of Map.Entry firstEntry() method of TreeMap 
import java.util.*;
public class FirstEntryOfTreeMap {
public static void main(String[] args) {
// Instantiates a TreeMap object
TreeMap < Integer, String > tree_map = new TreeMap < Integer, String > ();
// By using put() method is to add
// key-value pairs in a TreeMap
tree_map.put(10, "C");
tree_map.put(20, "C++");
tree_map.put(50, "JAVA");
tree_map.put(40, "PHP");
tree_map.put(30, "SFDC");
// Display TreeMap 
System.out.println("TreeMap: " + tree_map);
// By using firstEntry() method is to return
// the first entry with the least key value
// element exists in this TreeMap
System.out.println("tree_map.firstEntry(): " + tree_map.firstEntry());
}
}

Output

输出量

TreeMap: {10=C, 20=C++, 30=SFDC, 40=PHP, 50=JAVA}
tree_map.firstEntry(): 10=C

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

java treemap