Set

• Create set

Set<Integer> rollNumbers = new Set<Integer>{11008890, 11008100, 11007231};
System.debug(rollNumbers);

rollNumbers.add(89897767);
rollNumbers.add(89897764);
rollNumbers.add(89897765);

System.debug(rollNumbers);

// adding duplicate values - NOT ALLOWED
rollNumbers.add(89897767);
System.debug(rollNumbers);

• Check contains

// check if set has an item
System.debug(rollNumbers.contains(89897764));
System.debug(rollNumbers.contains(345345));

• Contain

// check if set has an item
System.debug(rollNumbers.contains(89897764));
System.debug(rollNumbers.contains(345345));

• Remove

// delete an item
rollNumbers.remove(89897765);
System.debug(rollNumbers);

• Length

// get set size
System.debug(rollNumbers.size());

• Check empty

// check if set is empty
System.debug(rollNumbers.isEmpty());

• Clear

// remove all items
rollNumbers.clear();
System.debug(rollNumbers.isEmpty());