40th: Set, Map, TreeSet, treemap operation code Combat

Let's take a look at the operation of set map today, so we start with the code

Val data = mutable. Set.empty[int]

Data ++= list (+/-)//Add to table on empty set

Data + = 4//Add new element to set

Data--= List (2,3)

println (data)//set (1, 4)
Data + = 1
println (data)//set (1, 4), stating that the Set element cannot be duplicated
Data.clear ()
println (data)//set ()

We can see that the set and list operations are roughly the same, but the important difference is that there are no duplicate elements in the set!

Let's take a look at map operations.

Val map = mutable. Map.empty[string,string]

Map ("java") = "Hadoop"
Map ("Scala") = "Spark"
println (map)//map (Scala, Spark, Java, Hadoop)
println (Map ("Scala"))//spark

Map stores data in the form of key value, and all keys, all of which are of the same type.

In fact, the set and map when adding elements, there is no order, but we actually apply, may need to have a sequence of set or map, then, the use of TreeSet and TreeMap

Val treeset = TreeSet (9,3,1,8,0,2,7,4,6,5)
println (treeset)//treeset (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)

Val Treesetforchar = TreeSet ("Spark", "Scala", "Hadoop")
println (Treesetforchar)//treeset (Hadoop, Scala, Spark)



var treemap=treemap ("Scala", "Spark", "Java", "Hadoop")

println (TREEMAP)//map (Java, Hadoop, Scala---Spark)

We can see that the printed results are well sequenced.

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40th: Set, Map, TreeSet, treemap operation code Combat