• Collection is the main interface.
  • There are many methods declared in Collection interface. These are the common methods for all collections to perform different operations.

  1. public interface Collection<E>
  2. extends Iterable<E>

Methods in Collection Interface:

 1.public Boolean add(Object obj)
  •  Used to add element in to the collection

 2.public Boolean addAll(Collection c)

  • Adds all the elements of c to the invoking collection. Returns true if the operation succeeded else returns false.

 3.public boolean isEmpty()
  • Returns true if collection is empty otherwise returns false.

 4.public boolean remove(Object obj)
  • Remove element from collection. Returns true if successful deletion.

5.public boolean  removeAll(Collection c)
  • Removes all elements of a collection.

 6.public void clear()
  • Deletes total elements from collection

 7.public boolean contains(Object obj)
  • This method used to search an element

 8.public boolean containsAll(Collection c)
  • This method used to search an element in a collection

 9.public boolean retianAll(Collection c)
  • Used to delete all elements from a collection except specified one.

10.public int size()
  • Returns total numbers of elements in a collection

11.public Iterator iterator()
  • Returns iterator for the collection

12.public boolean equals(Object obj)
  • Compares two collections

13.public int hashCode()
  • Returns hashcode

14.public Object[] toArray()
  • This method used to convert collection into array
15.public Object[] toArray(Object[] obj)
  • Returns an array containing only those collection elements whose type matches that of array.

Difference Between Collection and Collections:

  • Collection is the base interface for most of the classes.
  • Collections is the utility class.

Instance Of Java

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