The way you declare sets is similar to the way you declare lists. You can also have nested sets and sets of lists.
Ex:
// Empty set initialized
Set<String> strSet = new Set<String>();// Set of List of Strings
Set<List<String>> set2 = new Set<List<String>>();Some common methods of set:
| add(element) | Adds an element to set and only takes the argument of special datatype while declaring the set. | Set<String> s = new Set<String>(); s.add(‘abc’); s.add(‘ABC’); s.add(‘abc’); System.debug(s);//(‘abc’,’ABC’) |
| addAll(list/set) | Adds all of the elements in the specified list/set to the set if they are not already present. | List<String> l = new List<String>(); l.add(‘abc’); l.add(‘def’); s.addAll(l); System.debug(s);//(‘abc’,’ABC’,’def’) |
| clear() | Removes all the elements. | s.clear(); s.addAll(l); |
| clone() | Makes duplicate of a set. | List<String> s2 = s.clone(); System.debug(s);//(‘abc’,’def’) |
| contains(elm) | Returns true if the set contains the specified element. | Boolean result = s.contains(‘abc’); System.debug(result); // true |
| containsAll(list) | 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. | Boolean result = s.containsAll(l); System.debug(result); // true |
| size() | Returns the size of set. | System.debug(s.size()); // 2 |
| retainAll(list) | Retains only the elements in this set that are contained in the specified list and removes all other elements. | s.add(‘ghi’); System.debug(s);//(‘abc’,’def’,’ghi’) s.retainAll(l); System.debug(s);//(‘abc’,’def’) |
| remove(elm) | Removes the specified element from the set if it is present. | s.add(‘ghi’); s.remove(‘ghi’); System.debug(s);//(‘abc’,’def’) |
| removeAll(list) | Removes the elements in the specified list from the set if they are present. | s.add(‘ghi’); s.removeAll(l); System.debug(s);//(‘ghi’) |
