# Scala Set Examples: contains, intersect

Create a Set to store unique elements in a collection. Use contains and intersect.**Set.** On the beach, a great variety of seashells are visible. Suppose we want only unique ones. A set allows only distinct elements—it eliminates duplicates.

**With special operators,** like "++," we combine sets. In the two sets, any duplicate elements will be lost. Scala provides the Set type with simple syntax.

**First example.** This example uses a Set. It adds two elements to the set in the first line. With val we specify that our "animals" variable cannot be reassigned to something else.

**Immutable:** The set is immutable. To modify a set in Scala we can only create a new set, such as with a special operator.

**Contains:** This method returns true or false. It tells us whether the argument exists within the set.

**Scala program that uses set, contains**
*// Create a Set of two strings.
*val animals = __Set__(*"bird"*, *"fish"*)
println(animals)*
// See if this string is in the set.
*if (animals.__contains__(*"fish"*))
println(true)*
// This string is not contained in the set.
*println(animals.__contains__(*"apple"*))
**Output**
Set(bird, fish)
true
false

**Combine set.** Sets are immutable, so we cannot add or remove single elements of the existing collection. Instead we must create new sets with operators or methods.

**Here:** We use the "++" operator to combine two sets. Both sets have 15 as an element, and the resulting set has one instance of this value.

**Scala program that combines two sets**
*// Create two sets.
*val results1 = __Set__(10, 11, 15)
val results2 = __Set__(2, 3, 15)*
// Combine the sets.
// ... This eliminates duplicate elements.
// Ordering of elements is not retained.
*val results3 = results1 ++ results2*
// Display all sets.
*println(results1)
println(results2)
println(results3)
**Output**
Set(10, 11, 15)
Set(2, 3, 15)
Set(10, 2, 3, 11, 15)

**Intersect.** The intersection of two sets is the common elements of both sets. We compute an intersection with intersect() or an ampersand. Both map to the same function.

**Logic:** Set theory is an important part of mathematics. But for programs, it usually just makes some operations easier.

**Scala program that finds intersection**
val codes1 = Set(20, 21, 30)
val codes2 = Set(40, 20, 30)*
// Use intersect to find common elements of two sets.
*val result1 = codes1.__intersect__(codes2)
println(result1)*
// Short syntax for intersection.
*val result2 = codes1 & codes2
println(result2)
**Output**
Set(20, 30)
Set(20, 30)

**Research.** Sets in programming languages usually include methods like intersect(). And intersection is a core part of set theory. For a review, Wikipedia is a good choice.

**Quote:** Set theory is the branch of mathematical logic that studies sets, which informally are collections of objects.

Set theory: Wikipedia

**Sets are assets.** Set logic is helpful in some programs. A set is a map with no values: it can store a hashed lookup table of distinct keys. But no associated values may be added.

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