El método pollFirst() de TreeSet en Java se usa para recuperar y eliminar el primer elemento (el más bajo), o devuelve un valor nulo si este TreeSet está vacío.
Sintaxis:
E pollFirst()
Donde, E es el tipo de elementos que mantiene este contenedor TreeSet.
Parámetros: Esta función no acepta ningún parámetro.
Tipo de devolución: Devuelve el primer elemento del Treeset si TreeSet no está vacío, de lo contrario devuelve nulo.
Los siguientes programas ilustran el método pollFirst() en Java:
Ejemplo 1
// A Java program to demonstrate
// pollFirst() method of TreeSet
import java.util.TreeSet;
public class GFG {
public static void main(String[] args)
{
// creating TreeSet
TreeSet<Integer> ts = new TreeSet<Integer>();
// adding element to the TreeSet
ts.add(0);
ts.add(1);
ts.add(2);
ts.add(3);
ts.add(4);
ts.add(5);
ts.add(6);
// before removing element
System.out.println("Before removing " +
"element from TreeSet: " + ts);
// first element is removed
System.out.println("First lowest element " +
"removed is : " + ts.pollFirst());
System.out.println("After removing element" +
" from TreeSet: " + ts);
}
}
Producción:
Before removing element from TreeSet: [0, 1, 2, 3, 4, 5, 6] First lowest element removed is : 0 After removing element from TreeSet: [1, 2, 3, 4, 5, 6]
Ejemplo 2
// A Java program to demonstrate
// pollFirst() method of TreeSet
import java.util.TreeSet;
public class GFG {
public static void main(String[] args)
{
// creating TreeSet
TreeSet<String> ts = new TreeSet<String>();
// removing element when TreeSet
// is empty
System.out.println("pollFirst() method when " +
"TreeSet is empty : " + ts.pollFirst());
// adding element to the TreeSet
ts.add("Geeks");
ts.add("for");
ts.add("Geek");
// before removing element
System.out.println("Before removing element from" +
" TreeSet: " + ts);
// first element is removed
System.out.println("First lowest element removed is : "
+ ts.pollFirst());
System.out.println("After removing element " +
"from TreeSet: " + ts);
}
}
Producción:
pollFirst() method when TreeSet is empty : null Before removing element from TreeSet: [Geek, Geeks, for] First lowest element removed is : Geek After removing element from TreeSet: [Geeks, for]
Si TreeSet está vacío, este método devuelve nulo.
Ejemplo 3
// A Java program to demonstrate
// pollFirst() method of TreeSet
import java.util.TreeSet;
public class GFG {
public static void main(String[] args)
{
// creating TreeSet
TreeSet<Integer> ts = new TreeSet<Integer>();
// before removing element
System.out.println("Before removing " +
"element from TreeSet: " + ts);
// first element is removed
System.out.println("First lowest element " +
"removed is : " + ts.pollFirst());
System.out.println("After removing element" +
" from TreeSet: " + ts);
}
}
Producción:
Before removing element from TreeSet: [] First lowest element removed is : null After removing element from TreeSet: []
Publicación traducida automáticamente
Artículo escrito por ankit15697 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA