Java Language Sets Types and Usage of Sets


Example

Generally, sets are a type of collection which stores unique values. Uniqueness is determined by the equals() and hashCode() methods.

Sorting is determined by the type of set.

HashSet - Random Sorting

Java SE 7
Set<String> set = new HashSet<> ();
set.add("Banana");
set.add("Banana");
set.add("Apple");
set.add("Strawberry");

// Set Elements: ["Strawberry", "Banana", "Apple"]

LinkedHashSet - Insertion Order

Java SE 7
Set<String> set = new LinkedHashSet<> ();
set.add("Banana");
set.add("Banana");
set.add("Apple");
set.add("Strawberry");

// Set Elements: ["Banana", "Apple", "Strawberry"]

TreeSet - By compareTo() or Comparator

Java SE 7
Set<String> set = new TreeSet<> ();
set.add("Banana");
set.add("Banana");
set.add("Apple");
set.add("Strawberry");

// Set Elements: ["Apple", "Banana", "Strawberry"]
Java SE 7
Set<String> set = new TreeSet<> ((string1, string2) -> string2.compareTo(string1));
set.add("Banana");
set.add("Banana");
set.add("Apple");
set.add("Strawberry");

// Set Elements: ["Strawberry", "Banana", "Apple"]