Java Collection clear() Method with Examples

by Online Tutorials Library July 22, 2022

Java Collection clear() Method

The clear() method of Java Collection Interface removes all of the elements from this collection. It returns a Boolean value ‘true’, if it successfully empties the collection.

Syntax

Parameters

Throws

UnsupportedOperationException– if the clear operation is not supported by this collection.

Example 1

  import java.util.Collection;  import java.util.concurrent.LinkedBlockingDeque;  public class JavaCollectionClearExample1 {      public static void main(String[] args) {          Collection<Integer> collection = new LinkedBlockingDeque<Integer>();          collection.add(23);          collection.add(123);          collection.add(56);          System.out.println(“Collection : “+collection);          System.out.println(“After applying clear() method :  “);          // clear() method will erase the whole collection          collection.clear();          System.out.println(“Collection : “+collection);      }  }  

Test it Now

Output:

Collection : [23, 123, 56]  After applying clear() method :    Collection : []

Example 2

  import java.util.Collection;  import java.util.Scanner;  import java.util.concurrent.LinkedBlockingDeque;  class ShoppingList{      int SNo;      String Name;      public ShoppingList(int SNo, String name) {           this.SNo = SNo;          Name = name;      }      public String toString(){          return SNo+”. “+ Name ;      }  }  public class JavaCollectionClearExample2 {      public static void main(String[] args) {          Collection<ShoppingList> collection = new LinkedBlockingDeque<ShoppingList>();          ShoppingList list1 = new ShoppingList(1,”Sugar”);          ShoppingList list2= new ShoppingList(2,”Salt”);          ShoppingList list3 = new ShoppingList(3,”Potato”);          ShoppingList list4 = new ShoppingList(4,”Rice”);          collection.add(list1);          collection.add(list2);          collection.add(list3);          collection.add(list4);          for (ShoppingList xyz : collection ){              System.out.println(xyz);          }          Scanner scanner = new Scanner(System.in);          System.out.println(“Is Your shopping done.?”);          System.out.print(“true/false : “);          Boolean val = scanner.nextBoolean();          if(val.equals(true)){              // clear() method will erase the whole deque              collection.clear();              System.out.println(“Your queue has been emptied successfully.”);          }          else{              System.out.println(“Ok .You can add more items to your list”);          }      }  }  

Output:

1. Sugar  2. Salt  3. Potato  4. Rice  Is Your shopping done.?  true/false : true  Your queue has been emptied successfully.    Process finished with exit code 0

Example 3

  import java.util.Collection;  import java.util.concurrent.LinkedBlockingDeque;  public class JavaCollectionClearExample3 {      public static void main(String[] args) {          Collection<Integer> collection = new LinkedBlockingDeque<Integer>();          collection.add(23);          collection.add(null);          collection.add(56);          System.out.println(“Collection : “+collection);          System.out.println(“After applying clear() method :  “);          // clear() method will erase the whole collection          collection.clear();          System.out.println(“Collection : “+collection);      }  }  

Test it Now

Output:

Exception in thread "main" java.lang.NullPointerException  at java.util.concurrent.LinkedBlockingDeque.offerLast(LinkedBlockingDeque.java:357)  at java.util.concurrent.LinkedBlockingDeque.addLast(LinkedBlockingDeque.java:334)  at java.util.concurrent.LinkedBlockingDeque.add(LinkedBlockingDeque.java:633)  at com.tutorAspire.JavaCollectionClearExample3.main(JavaCollectionClearExample3.java:9)

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Java Collection clear() Method with Examples

Java Collection clear() Method

Syntax

Parameters

Throws

Example 1

Example 2

Example 3

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