Operations on a set

Create the set

Set set = new HashSet();

 

Add elements to the set

set.add("a");
set.add("b"); 
set.add("c"); 

Remove elements from the set

set.remove("c"); 

Get number of elements in set

int size = set.size(); // 2

Adding an element that already exists in the set has no effect
 

set.add("a"); 
size = set.size(); // 2

Determining if an element is in the set

boolean b = set.contains("a"); // true
b = set.contains("c"); // false //

Iterating over the elements in the set

Iterator it = set.iterator();
while (it.hasNext()) {
  // Get element
  Object element = it.next();
}

Create an array containing the elements in the set (in this case a String array)

String[] array = (String[])set.toArray(new String[set.size()]);

 

See also Operations on 2 Sets in java