The isEmpty() of java.util.Collection interface is used to check if the Collection upon which it is called is empty or not. This method does not take any parameter and does not returns any value.
Syntax:
Collection.isEmpty()
Parameters: This method do not accept any parameter
Return Value: This method does not return any value.
Below examples illustrate the Collection isEmpty() method:
Example 1: Using LinkedList Class
// Java code to illustrate boolean isEmpty() method import java.io.*;
import java.util.*;
public class GFG {
public static void main(String args[])
{
// creating an empty LinkedList
Collection<String> list = new LinkedList<String>();
// use add() method to add elements in the list
list.add( "Geeks" );
list.add( "for" );
list.add( "Geeks" );
// Output the present list
System.out.println( "The list is: " + list);
// Check if list is empty
// using isEmpty() method
System.out.println( "Is the LinkedList empty: "
+ list.isEmpty());
// Clearing the LinkedList
list.clear();
// printing the new list
System.out.println( "The new List is: " + list);
// Check if list is empty
// using isEmpty() method
System.out.println( "Is the LinkedList empty: "
+ list.isEmpty());
}
} |
Output:
The list is: [Geeks, for, Geeks] Is the LinkedList empty: false The new List is: [] Is the LinkedList empty: true
Example 2: Using ArrayDeque Class
// Java code to illustrate isEmpty() method import java.util.*;
public class ArrayDequeDemo {
public static void main(String args[])
{
// Creating an empty ArrayDeque
Collection<String> de_que = new ArrayDeque<String>();
// Use add() method to add elements into the Deque
de_que.add( "Welcome" );
de_que.add( "To" );
de_que.add( "Geeks" );
de_que.add( "4" );
de_que.add( "Geeks" );
// Displaying the ArrayDeque
System.out.println( "ArrayDeque: " + de_que);
// Check if ArrayDeque is empty
// using isEmpty() method
System.out.println( "Is the ArrayDeque empty: "
+ de_que.isEmpty());
// Clearing the ArrayDeque
de_que.clear();
// printing the new ArrayDeque
System.out.println( "The new ArrayDeque is: "
+ de_que);
// Check if ArrayDeque is empty
// using isEmpty() method
System.out.println( "Is the ArrayDeque empty: "
+ de_que.isEmpty());
}
} |
Output:
ArrayDeque: [Welcome, To, Geeks, 4, Geeks] Is the ArrayDeque empty: false The new ArrayDeque is: [] Is the ArrayDeque empty: true
Example 3: Using ArrayList Class
// Java code to illustrate isEmpty() method import java.io.*;
import java.util.*;
public class ArrayListDemo {
public static void main(String[] args)
{
// create an empty array list with an initial capacity
Collection<Integer>
arrlist = new ArrayList<Integer>( 5 );
// use add() method to add elements in the list
arrlist.add( 15 );
arrlist.add( 20 );
arrlist.add( 25 );
// prints all the elements available in list
System.out.println( "ArrayList: " + arrlist);
// Check if list is empty
// using isEmpty() method
System.out.println( "Is the ArrayList empty: "
+ arrlist.isEmpty());
// Clearing the ArrayList
arrlist.clear();
// printing the new ArrayList
System.out.println( "The new ArrayList is: "
+ arrlist);
// Check if ArrayList is empty
// using isEmpty() method
System.out.println( "Is the ArrayList empty: "
+ arrlist.isEmpty());
}
} |
Output:
ArrayList: [15, 20, 25] Is the ArrayList empty: false The new ArrayList is: [] Is the ArrayList empty: true
Reference: https://docs.oracle.com/javase/9/docs/api/java/util/Collection.html#isEmpty–