Java 中 SortedMap 比较器()方法示例
原文:https://www . geesforgeks . org/sorted map-comparator-in-method-in-Java-with-examples/
java.util.SortedMap 接口的比较器()方法用于返回用于对该地图中的键进行排序的比较器，如果该地图使用其键的自然排序，则返回 null。 语法:
public Comparator comparator()
返回值:该方法返回用于对该地图中的关键点进行排序的比较器，如果该地图使用其关键点的自然排序，则返回 null。 下面的程序说明了比较器()方法: 例 1: 为自然排序。
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to demonstrate
// comparator() method for natural ordering
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
// Creating object of SortedTreeMap
SortedMap<Integer, String>
sotreemap = new TreeMap<Integer, String>();
// Populating tree map
sotreemap.put(1, "one");
sotreemap.put(2, "two");
sotreemap.put(3, "three");
sotreemap.put(4, "four");
sotreemap.put(5, "five");
// Printing the SortedTreeMap
System.out.println("SortedTreeMap: " + sotreemap);
// Getting used Comparator in the map
// using comparator() method
Comparator comp = sotreemap.comparator();
// Printing the comparator value
System.out.println("Comparator value: "
+ comp);
}
catch (NullPointerException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Output:
SortedTreeMap: {1=one, 2=two, 3=three, 4=four, 5=five}
Comparator value: null
例 2: 为逆序。
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to demonstrate
// comparator() method
// for reverse ordering
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception<div class="code-output">
<b>Output:</b>
<pre>
Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
The set is: [10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You]
</pre>
</div>
{
try {
// Creating object of TreeMap
SortedMap<Integer, String>
sotreemap = new TreeMap<Integer, String>(
Collections.reverseOrder());
// Populating tree map
sotreemap.put(1, "one");
sotreemap.put(2, "two");
sotreemap.put(3, "three");
sotreemap.put(4, "four");
sotreemap.put(5, "five");
// Printing the TreeMap
System.out.println("SortedTreeMap: " + sotreemap);
// Getting used Comparator in the map
// using comparator() method
Comparator comp = sotreemap.comparator();
// Printing the comparator value
System.out.println("Comparator value: " + comp);
}
catch (NullPointerException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Output:
SortedTreeMap: {5=five, 4=four, 3=three, 2=two, 1=one}
Comparator value: java.util.Collections$ReverseComparator@232204a1
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