java.util.SortedMap接口的comparator()方法用于返回用于对该映射中的键进行排序的比较器;如果此映射使用其键的自然顺序,则返回null。
用法:
public Comparator comparator()
返回值:此方法返回用于对该映射中的键进行排序的比较器;如果此映射使用其键的自然顺序,则返回null。
以下示例程序旨在说明comparator()方法:
范例1:对于自然排序。
// 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");
// Pritnig the SortedTreeMap
System.out.println("SortedTreeMap:" + sotreemap);
// Getting used Comparator in the map
// using comparator() method
Comparator comp = sotreemap.comparator();
// Pritnig the comparator value
System.out.println("Comparator value:"
+ comp);
}
catch (NullPointerException e) {
System.out.println("Exception thrown:" + e);
}
}
}
输出:
SortedTreeMap:{1=one, 2=two, 3=three, 4=four, 5=five} Comparator value:null
范例2:用于反向排序。
// 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 = 'outputDiv'>
<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");
// Pritnig the TreeMap
System.out.println("SortedTreeMap:" + sotreemap);
// Getting used Comparator in the map
// using comparator() method
Comparator comp = sotreemap.comparator();
// Pritnig the comparator value
System.out.println("Comparator value:" + comp);
}
catch (NullPointerException e) {
System.out.println("Exception thrown:" + e);
}
}
}
输出:
SortedTreeMap:{5=five, 4=four, 3=three, 2=two, 1=one} Comparator value:java.util.Collections$ReverseComparator@232204a1
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注:本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 SortedMap comparator() method in Java with Examples。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。