Set contains() method in Java with Examples

Set.contains() method in Java is used to check if a specific element exists in a Set. It returns true if the element is present, otherwise false. This method is useful for quickly verifying membership in collections that do not allow duplicates, like HashSet or TreeSet.

Example:

Does the set contain Apple?: true
Does the set contain Orange?: false

Explanation:

• Set<String> fruits = new HashSet<>(): creates a HashSet.
• contains() checks whether "Apple" and "Orange" exist in the set.
• "Apple" exists, so it returns true; "Orange" does not, so it returns false.

Syntax

boolean contains(Object element)

• Parameters: "element" to check for in the set.
• Return Value: returns true if the set contains the specified element, false otherwise

Example:This code shows how Set.contains() checks for an element in a HashSet.

Set: [4, Geeks, Welcome, To]
Does the Set contain 'Geeks'?: true
Does the Set contain '4'?: true
Does the Set contain 'No'?: false

Explanation:

• Duplicate entries are ignored automatically in a Set.
• contains() checks for the presence of an element in the set.
• The method returns true for existing elements and false for elements not in the set.

Note:Works for all Set types (HashSet, TreeSet, LinkedHashSet), has O(1) time complexity for HashSet.contains().

Related Topics:

• Set in Java
• Difference and similarities between HashSet, LinkedHashSet and TreeSet in Java
• Collections in Java