Java 中的 Java . util . TreeMap . DecendingMap()和 DecendingKeySet()
原文:https://www . geesforgeks . org/Java-util-tree map-depending map-depending keyset-Java/
Java.util.TreeMap 中有两个降序()的**变体，本文将对这两个变体进行讨论。
1。下行键集():返回地图中包含的键的逆序导航集视图。**
**Syntax :**
public NavigableSet descendingKeySet()
**Parameters:**
**NA**
**Return Value:**
It returns a reverse order navigable set view of the keys in this map.
**Exception:**
**NA**
// Java code to demonstrate the working
// descendingKeySet()
import java.io.*;
import java.util.*;
public class descendingKeySet1 {
public static void main(String[] args)
{
// Declaring the tree map of Integer and String
TreeMap<Integer, String> treemap = new TreeMap<Integer, String>();
// assigning the values in the tree map
// using put()
treemap.put(2, "two");
treemap.put(0, "zero");
treemap.put(3, "three");
treemap.put(6, "six");
treemap.put(9, "nine");
treemap.put(7, "seven");
// putting values in navigable set
// use of descendingKeySet
NavigableSet set1 = treemap.descendingKeySet();
System.out.println("Navigable set values are: " + set1);
}
}
输出:
Navigable set values are: [9, 7, 6, 3, 2, 0]
*2。下行映射():*返回映射中包含的映射的逆序视图。****
**Syntax :**
public NavigableMap descendingMap()
**Parameters:**
**NA**
**Return Value**
It returns a reverse order view of the map.
**Exception:**
**NA**
// Java code to demonstrate the working
// of descendingMap()
import java.io.*;
import java.util.*;
public class descendingMap {
public static void main(String[] args)
{
// Declaring the tree map of Integer and String
TreeMap<Integer, String> treemap = new TreeMap<Integer, String>();
// assigning the values in the tree map
// using put()
treemap.put(2, "two");
treemap.put(0, "zero");
treemap.put(3, "three");
treemap.put(6, "six");
treemap.put(9, "nine");
treemap.put(7, "seven");
// putting values in navigable map
// use of descendingMap()
NavigableMap map1 = treemap.descendingMap();
System.out.println("Navigable map values are: " + map1);
}
}
输出:
Navigable map values are: {9=nine, 7=seven, 6=six, 3=three, 2=two, 0=zero}
*实际应用:*本文解释的下降函数有很多可能的应用。其中一些是优先调度，或者设计一个排名系统。下面的代码演示了后一种方法。
// Java code to demonstrate the application
// of descendingMap() and descendingKetSet()
import java.io.*;
import java.util.*;
public class descendingAppli {
public static void main(String[] args)
{
// Declaring the tree map of Integer and String
// to store participants info of scores with name
TreeMap<Integer, String> participants = new TreeMap<Integer, String>();
// assigning score of participants
// using put()
participants.put(30, "Ashty");
participants.put(45, "Shavi");
participants.put(16, "Vaish");
participants.put(15, "Kil");
participants.put(11, "Manju");
// putting ranks in NavigableMap
// use of descendingMap() to assign 1st to
// maximum values and so on
NavigableMap<Integer, String> Ranks = participants.descendingMap();
System.out.println("The ranks according to scores are : ");
// Printing values rankwise
int count = 0;
for (NavigableMap.Entry<Integer, String> entry : Ranks.entrySet()) {
count++;
String str = Integer.toString(count);
System.out.println("Rank " + str + ": " + entry.getValue());
}
}
}
输出:
The ranks according to scores are :
Rank 1: Shavi
Rank 2: Ashty
Rank 3: Vaish
Rank 4: Kil
Rank 5: Manju
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