--- schema_version: "1" id: d9a937cb220912814df7e95ca45e703a53826cc86c6968a1d4196b434885300a title: Set Class collection: legacydeveloper version: current locale: en-us portal_url: https://docs.salesforce.com/legacydeveloper/current/en-us/apexref/apex_methods_system_set.md canonical_url: https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm source_site: developer.salesforce.com content_type: documentation content_hash: 81642e7d38ae9a0c50bd33e4570c2dc3cd18cf32d96631c9499a448013e15ffa description: Represents a collection of unique elements with no duplicate values.Creates a new instance of the Set class. A set can hold elements of any data type T.Creates a new instance of the Set class by copying the elements of the specified set. T is the data type of the elements in both sets and can be any data type.Creates a new instance of the Set class by copying the list elements. T is the data type of the elements in the set and list and can be any data type.Adds an element to the set if it is not already present.Adds all of the elements in the specified list to the set if they are not already present.Adds all of the elements in the specified set to the set that calls the method if they are not already present.Removes all of the elements from the set.Makes a duplicate copy of the set.Returns true if the set contains the specified element.Returns true if the set contains all of the elements in the specified list. The list must be of the same type as the set that calls the method. Returns true if the set contains all of the elements in the specified set. The specified set must be of the same type as the original set that calls the method.Compares this set with the specified set and returns true if both sets are equal; otherwise, returns false.Returns the hashcode corresponding to this set and its contents.Returns true if the set has zero elements.Removes the specified element from the set if it is present.Removes the elements in the specified list from the set if they are present. Removes the elements in the specified set from the original set if they are present. Retains only the elements in this set that are contained in the specified list.Retains only the elements in the original set that are contained in the specified set.Returns the number of elements in the set (its cardinality).Returns the string representation of the set. --- # Set Class Represents a collection of unique elements with no duplicate values. ## Namespace [System](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_namespace_System.htm "The System namespace provides classes and methods for core Apex functionality.") ## Usage The Set methods work on a set, that is, an unordered collection of elements that was initialized using the set keyword. Set elements can be of any data type—primitive types, collections, sObjects, user-defined types, and built-in Apex types. Set methods are all instance methods, that is, they all operate on a particular instance of a Set. The following are the instance methods for sets. ![Note](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/images/icon_note.png) #### Note - Uniqueness of set elements of user-defined types is determined by the [equals and hashCode methods](https://developer.salesforce.com/docs/atlas.en-us.264.0.apexcode.meta/apexcode/langCon_apex_collections_maps_keys_userdefined.htm), which you provide in your classes. Uniqueness of all other non-primitive types is determined by comparing the objects’ fields. - If the set contains String elements, the elements are case-sensitive. Two set elements that differ only by case are considered distinct. For more information on sets, see [Sets](https://developer.salesforce.com/docs/atlas.en-us.264.0.apexcode.meta/apexcode/langCon_apex_collections_sets.htm). - **[Set Constructors](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_constructors)** - **[Set Methods](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_methods)** ## Set Constructors The following are constructors for Set. - **[Set()](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_ctor_3)** Creates a new instance of the Set class. A set can hold elements of any data type T. - **[Set(setToCopy)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_ctor_2)** Creates a new instance of the Set class by copying the elements of the specified set. T is the data type of the elements in both sets and can be any data type. - **[Set(listToCopy)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_ctor)** Creates a new instance of the Set class by copying the list elements. T is the data type of the elements in the set and list and can be any data type. ### Set() Creates a new instance of the Set class. A set can hold elements of any data type T. #### Signature public Set() #### Example // Create a set of strings Set s1 = new Set(); // Add two strings to it s1.add('item1'); s1.add('item2'); ### Set(setToCopy) Creates a new instance of the Set class by copying the elements of the specified set. T is the data type of the elements in both sets and can be any data type. #### Signature public Set(Set setToCopy) #### Parameters - **setToCopy**: Type: Set The set to initialize this set with. #### Example Set s1 = new Set(); s1.add('item1'); s1.add('item2'); Set s2 = new Set(s1); // The set elements in s2 are copied from s1 System.debug(s2); ### Set(listToCopy) Creates a new instance of the Set class by copying the list elements. T is the data type of the elements in the set and list and can be any data type. #### Signature public Set(List listToCopy) #### Parameters - **listToCopy**: Type: [Integer](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_integer.htm#apex_methods_system_integer "Contains methods for the Integer primitive data type.") The list to copy the elements of into this set. #### Example List ls = new List(); ls.add(1); ls.add(2); // Create a set based on a list Set s1 = new Set(ls); // Elements are copied from the list to this set System.debug(s1);// DEBUG|{1, 2} ## Set Methods The following are methods for Set. All are instance methods. - **[add(setElement)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_add)** Adds an element to the set if it is not already present. - **[addAll(fromList)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_addAll)** Adds all of the elements in the specified list to the set if they are not already present. - **[addAll(fromSet)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_addAll_2)** Adds all of the elements in the specified set to the set that calls the method if they are not already present. - **[clear()](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_clear)** Removes all of the elements from the set. - **[clone()](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_clone)** Makes a duplicate copy of the set. - **[contains(setElement)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_contains)** Returns true if the set contains the specified element. - **[containsAll(listToCompare)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_containsAll)** Returns true if the set contains all of the elements in the specified list. The list must be of the same type as the set that calls the method. - **[containsAll(setToCompare)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_containsAll_2)** Returns true if the set contains all of the elements in the specified set. The specified set must be of the same type as the original set that calls the method. - **[equals(set2)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_equals)** Compares this set with the specified set and returns true if both sets are equal; otherwise, returns false. - **[hashCode()](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_hashCode)** Returns the hashcode corresponding to this set and its contents. - **[isEmpty()](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_isEmpty)** Returns true if the set has zero elements. - **[remove(setElement)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_remove)** Removes the specified element from the set if it is present. - **[removeAll(listOfElementsToRemove)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_removeAll)** Removes the elements in the specified list from the set if they are present. - **[removeAll(setOfElementsToRemove)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_removeAll_2)** Removes the elements in the specified set from the original set if they are present. - **[retainAll(listOfElementsToRetain)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_retainAll)** Retains only the elements in this set that are contained in the specified list. - **[retainAll(setOfElementsToRetain)](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_retainAll_2)** Retains only the elements in the original set that are contained in the specified set. - **[size()](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_size)** Returns the number of elements in the set (its cardinality). - **[toString()](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_set.htm#apex_System_Set_toString)** Returns the string representation of the set. ### add(setElement) Adds an element to the set if it is not already present. #### Signature public Boolean add(Object setElement) #### Parameters - **setElement**: Type: Object #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") #### Usage This method returns true if the original set changed as a result of the call. For example: Set myString = new Set{'a', 'b', 'c'}; Boolean result = myString.add('d'); Assert.isTrue(result); ### addAll(fromList) Adds all of the elements in the specified list to the set if they are not already present. #### Signature public Boolean addAll(List fromList) #### Parameters - **fromList**: Type: [List](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_list.htm#apex_methods_system_list "Contains methods for the List collection type.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") Returns true if the original set changed as a result of the call. #### Usage This method results in the _union_ of the list and the set. The list must be of the same type as the set that calls the method. ### addAll(fromSet) Adds all of the elements in the specified set to the set that calls the method if they are not already present. #### Signature public Boolean addAll(Set fromSet) #### Parameters - **fromSet**: Type: [Set](#apex_methods_system_set "Represents a collection of unique elements with no duplicate values.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") This method returns true if the original set changed as a result of the call. #### Usage This method results in the _union_ of the two sets. The specified set must be of the same type as the original set that calls the method. #### Example Set myString = new Set{'a', 'b'}; Set sString = new Set{'c'}; Boolean result1 = myString.addAll(sString); Assert.isTrue(result1); ### clear() Removes all of the elements from the set. #### Signature public Void clear() #### Return Value Type: Void ### clone() Makes a duplicate copy of the set. #### Signature public Set clone() #### Return Value Type: [Set](#apex_methods_system_set "Represents a collection of unique elements with no duplicate values.") (of same type) ### contains(setElement) Returns true if the set contains the specified element. #### Signature public Boolean contains(Object setElement) #### Parameters - **setElement**: Type: Object #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") #### Example Set myString = new Set{'a', 'b'}; Boolean result = myString.contains('z'); Assert.isFalse(result); ### containsAll(listToCompare) Returns true if the set contains all of the elements in the specified list. The list must be of the same type as the set that calls the method. #### Signature public Boolean containsAll(List listToCompare) #### Parameters - **listToCompare**: Type: [List](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_list.htm#apex_methods_system_list "Contains methods for the List collection type.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") ### containsAll(setToCompare) Returns true if the set contains all of the elements in the specified set. The specified set must be of the same type as the original set that calls the method. #### Signature public Boolean containsAll(Set setToCompare) #### Parameters - **setToCompare**: Type: [Set](#apex_methods_system_set "Represents a collection of unique elements with no duplicate values.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") #### Example Set myString = new Set{'a', 'b'}; Set sString = new Set{'c'}; Set rString = new Set{'a', 'b', 'c'}; Boolean result1, result2; result1 = myString.addAll(sString); Assert.isTrue(result1); result2 = myString.containsAll(rString); Assert.isTrue(result2); ### equals(set2) Compares this set with the specified set and returns true if both sets are equal; otherwise, returns false. #### Signature public Boolean equals(Set set2) #### Parameters - **set2**: Type: [Set](#apex_methods_system_set "Represents a collection of unique elements with no duplicate values.") The set2 argument is the set to compare this set with. #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") #### Usage Two sets are equal if their elements are equal, regardless of their order. The \== operator is used to compare the elements of the sets. The \== operator is equivalent to calling the equals method, so you can call set1.equals(set2); instead of set1 == set2;. ### hashCode() Returns the hashcode corresponding to this set and its contents. #### Signature public Integer hashCode() #### Return Value Type: [Integer](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_integer.htm#apex_methods_system_integer "Contains methods for the Integer primitive data type.") ### isEmpty() Returns true if the set has zero elements. #### Signature public Boolean isEmpty() #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") #### Example Set mySet = new Set(); Boolean result = mySet.isEmpty(); Assert.isTrue(result); ### remove(setElement) Removes the specified element from the set if it is present. #### Signature public Boolean remove(Object setElement) #### Parameters - **setElement**: Type: Object #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") Returns true if the original set changed as a result of the call. ### removeAll(listOfElementsToRemove) Removes the elements in the specified list from the set if they are present. #### Signature public Boolean removeAll(List listOfElementsToRemove) #### Parameters - **listOfElementsToRemove**: Type: [List](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_list.htm#apex_methods_system_list "Contains methods for the List collection type.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") Returns true if the original set changed as a result of the call. #### Usage This method results in the relative complement of the two sets. The list must be of the same type as the set that calls the method. #### Example Set mySet = new Set{1, 2, 3}; List myList = new List{1, 3}; Boolean result = mySet.removeAll(myList); Assert.isTrue(result); Integer result2 = mySet.size(); Assert.areEqual(1, result2); ### removeAll(setOfElementsToRemove) Removes the elements in the specified set from the original set if they are present. #### Signature public Boolean removeAll(Set setOfElementsToRemove) #### Parameters - **setOfElementsToRemove**: Type: [Set](#apex_methods_system_set "Represents a collection of unique elements with no duplicate values.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") This method returns true if the original set changed as a result of the call. #### Usage This method results in the relative complement of the two sets. The specified set must be of the same type as the original set that calls the method. ### retainAll(listOfElementsToRetain) Retains only the elements in this set that are contained in the specified list. #### Signature public Boolean retainAll(List listOfElementsToRetain) #### Parameters - **listOfElementsToRetain**: Type: [List](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_list.htm#apex_methods_system_list "Contains methods for the List collection type.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") This method returns true if the original set changed as a result of the call. #### Usage This method results in the _intersection_ of the list and the set. The list must be of the same type as the set that calls the method. #### Example Set mySet = new Set{1, 2, 3}; List myList = new List{1, 3}; Boolean result = mySet.retainAll(myList); Assert.isTrue(result); ### retainAll(setOfElementsToRetain) Retains only the elements in the original set that are contained in the specified set. #### Signature public Boolean retainAll(Set setOfElementsToRetain) #### Parameters - **setOfElementsToRetain**: Type: [Set](#apex_methods_system_set "Represents a collection of unique elements with no duplicate values.") #### Return Value Type: [Boolean](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_boolean.htm#apex_methods_system_boolean "Contains methods for the Boolean primitive data type.") Returns true if the original set changed as a result of the call. #### Usage This method results in the _intersection_ of the two sets. The specified set must be of the same type as the original set that calls the method. ### size() Returns the number of elements in the set (its cardinality). #### Signature public Integer size() #### Return Value Type: [Integer](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_integer.htm#apex_methods_system_integer "Contains methods for the Integer primitive data type.") #### Example Set mySet = new Set{1, 2, 3}; Set retainSet = new Set{1, 3}; Boolean result = mySet.retainAll(retainSet); Assert.isTrue(result, 'Expected to have changed mySet'); Integer retainedSetSize = mySet.size(); Assert.areEqual(2, retainedSetSize); ### toString() Returns the string representation of the set. #### Signature public String toString() #### Return Value Type: [String](https://developer.salesforce.com/docs/atlas.en-us.apexref.meta/apexref/apex_methods_system_string.htm#apex_methods_system_string "Contains methods for the String primitive data type.") #### Usage When used in cyclic references, the output is truncated to prevent infinite recursion. When used with large collections, the output is truncated to avoid exceeding total heap size and maximum CPU time. - Up to 10 items per collection are included in the output, followed by an ellipsis (…). - If the same object is included multiple times in a collection, it’s shown in the output only once; subsequent references are shown as (already output).