Java.util.TreeMap también contiene funciones que admiten la recuperación y eliminación de valores tanto altos como bajos y, por lo tanto, brindan mucha flexibilidad en la aplicabilidad y el uso diario. Esta función es poll() y tiene 2 variantes discutidas en este artículo.
1. pollFirstEntry() : elimina y recupera un par clave-valor con el menor valor clave en el mapa y «null» es que el mapa está vacío.
Syntax : public Map.Entry pollFirstEntry() Parameters: NA Return Value: Retrieves and removes the least key-value if map is filled else returns null. Exception: NA
// Java code to demonstrate the working
// of pollFirstEntry()
import java.io.*;
import java.util.*;
public class pollFirstEntry {
public static void main(String[] args)
{
// Declaring the tree map of String and Integer
TreeMap<String, Integer> tmp = new TreeMap<String, Integer>();
// Trying to retrieve and remove in empty map
// returns null
System.out.println
("The smallest key value pair is : " + tmp.pollFirstEntry());
// assigning the values in the tree map
// using put()
tmp.put("Geeks", 1);
tmp.put("for", 4);
tmp.put("geeks", 1);
// Printing the initial map
System.out.println
("The initial Map before deletion is : " + tmp);
// Use of pollFirstEntry()
// Removes the first entry and returns the least key
// lexicographically smallest in case of String
// prints Geeks-1
System.out.println
("The smallest key value pair is : " + tmp.pollFirstEntry());
// Printing the map after deletion
System.out.println
("The resultant Map after deletion is : " + tmp);
}
}
Producción:
The smallest key value pair is : null
The initial Map before deletion is : {Geeks=1, for=4, geeks=1}
The smallest key value pair is : Geeks=1
The resultant Map after deletion is : {for=4, geeks=1}
2. pollLastEntry() : Elimina y recupera un par clave-valor con el valor clave más grande en el mapa y «null» es que el mapa está vacío.
Syntax : public Map.Entry pollLastEntry() Parameters: NA Return Value: Retrieves and removes the largest key-value if map is filled else returns null. Exception: NA
// Java code to demonstrate the working
// of pollLastEntry()
import java.io.*;
import java.util.*;
public class pollLastEntry {
public static void main(String[] args)
{
// Declaring the tree map of String and Integer
TreeMap<String, Integer> tmp = new TreeMap<String, Integer>();
// Trying to retrieve and remove in empty map
// returns null
System.out.println
("The largest key value pair is : " + tmp.pollFirstEntry());
// assigning the values in the tree map
// using put()
tmp.put("Geeks", 1);
tmp.put("for", 4);
tmp.put("geeks", 1);
// Printing the initial map
System.out.println
("The initial Map before deletion is : " + tmp);
// Use of pollLastEntry()
// Removes the last(max) entry and returns the max key
// lexicographically greatest in case of String
// prints geeks-1
System.out.println
("The largest key value pair is : " + tmp.pollLastEntry());
// Printing the map after deletion
System.out.println
("The resultant Map after deletion is : " + tmp);
}
}
Producción:
The largest key value pair is : null
The initial Map before deletion is : {Geeks=1, for=4, geeks=1}
The largest key value pair is : geeks=1
The resultant Map after deletion is : {Geeks=1, for=4}
Aplicación práctica: Hay muchas aplicaciones que se pueden pensar utilizando el concepto de deque o colas de prioridad. Un ejemplo de este tipo se muestra en el siguiente código.
// Java code to demonstrate the application
// of pollLastEntry() and pollFirstEntry()
import java.io.*;
import java.util.*;
public class pollAppli {
public static void main(String[] args)
{
// Declaring the tree map of Integer and String
TreeMap<Integer, String> que = new TreeMap<Integer, String>();
// assigning the values in que
// using put()
que.put(10, "astha");
que.put(4, "shambhavi");
que.put(7, "manjeet");
que.put(8, "nikhil");
// Defining the priority
// takes highest value, if priority is high
// else takes lowest value
String prio = "high";
// Printing the initial queue
System.out.println("The initial queue is : " + que);
if (prio == "high") {
System.out.println
("The largest valued person is : " + que.pollLastEntry());
System.out.println
("The resultant queue after deletion is : " + que);
}
else {
System.out.println
("The lowest valued person is : " + que.pollFirstEntry());
System.out.println
("The resultant queue after deletion is : " + que);
}
}
}
Producción:
The initial queue is : {4=shambhavi, 7=manjeet, 8=nikhil, 10=astha}
The largest valued person is : 10=astha
The resultant queue after deletion is : {4=shambhavi, 7=manjeet, 8=nikhil}
Publicación traducida automáticamente
Artículo escrito por Shambhavi Singh 1 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA