Sets

This table represents a set of strings that uses city names:

Sets can contain collections that can be nested within one another. For example, you can have a set of lists of sets of Integers. A set can contain up to seven levels of nested collections inside it, that is, up to eight levels overall.

Set<String> myStringSet = new Set<String>();

The following example shows how to create a set with two hardcoded string values.

// Defines a new set with two elements
Set<String> set1 = new Set<String>{'New York', 'Paris'};

To access elements in a set, use the system methods provided by Apex. For example:

// Define a new set
Set<Integer> mySet = new Set<Integer>();
// Add two elements to the set
mySet.add(1);
mySet.add(3);
// Assert that the set contains the integer value we added
System.assert(mySet.contains(1)); 
// Remove the integer value from the set
mySet.remove(1);

The following example shows how to create a set from elements of another set.

// Define a new set that contains the
// elements of the set created in the previous example
Set<Integer> mySet2 = new Set<Integer>(mySet);
// Assert that the set size equals 1
// Note: The set from the previous example contains only one value
System.assert(mySet2.size() == 1);

For more information, including a complete list of all supported set system methods, see Set Class.