treemap比较器

TreeMap类的compare()方法 (TreeMap Class comparator() method)

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

  比较器()方法在java.util包中可用。

• comparator() method is used to return the key element in this TreeMap based on the Comparator object otherwise it returns null when this TreeMap follows default ordering the key elements.

  比较器()方法用于根据Comparator对象返回此TreeMap中的关键元素，否则，当此TreeMap遵循默认的关键元素顺序时，它将返回null。

• comparator() 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.

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

• comparator() method does not throw an exception at the time of returning the Comparator object.

  返回Comparator对象时，compareor ()方法不会引发异常。

Syntax:

句法：

    public Comparator comparator();

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 Comparator, it returns Comparator object will result in ordering the key element otherwise it returns null when this TreeMap will result in default ordering the key element.

该方法的返回类型为Comparator ，它返回Comparator对象将导致对key元素进行排序，否则，当此TreeMap导致对key元素进行默认排序时，它将返回null。

Example:

例：

// Java program to demonstrate the example 
// of Comparator comparator() method of TreeMap 
import java.util.*;
public class ComparatorOfTreeMap {
public static void main(String[] args) {
// Instantiates a TreeMap object
NavigableMap < 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 comparator() method is to
// return the comparator object
Comparator com = tree_map.comparator();
// Display Comparator
System.out.println("tree_map.comparator(): " + com);
}
}

Output

输出量

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

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

treemap比较器