Original Scala Learning: tuple,array,map, file manipulation

1.Tuple: Yuan zu. is a useful container object.

1) Features:

① Yuan zu is immutable, that is, when the declaration of a meta-ancestor, then its length can not be changed;

② can contain different types of data, objects;

③ index is starting with ' _1 ' to read the contents of the meta-ancestor

④ ID: ' () '

2) Code

1   // Ganso 2   def dotuple () {3     //' () ' defines meta-ancestor 4     //  Ganso type val pair: (Int, String, string) pushed down by Scala type 5    println (pair._1)6     println (pair._2) 7   }

　　　

2.Array: Parameterized array of type

1) Features:

① means to create an instance and complete its "settings", that is, to assign values;

The ②scala array is accessed by an indexed value with parentheses, array (i), and different from the square brackets in Java;

The length of the ③array is immutable, but its value is variable;

2) Code:

1   //Array2 def doarray () {3     //defining an array with the array keyword4Val Array = Array (1, 2, 3, 4, 5)5     //For (i <-0 until Array.Length) {6     //println (Array (i))7     //      }8 9     //enhanced for loop, recommendedTen      for(Elemt <-array) println (ELEMT) One  A}

3.Map

1  //Map Operations2 def domap () {3     //define a map with the map keyword4Val ages = Map ("Jason", "Hadoop", 20))5 6      for(k, V) <-ages) println ("Key is:" + K + ", Hadoop is:" + V)//key Is:jason, Hadoop is:27 key Is:hadoop, Hadoop is:207 8     //"_" is a placeholder9     //For ((k,_) <-ages) println ("Key is:" + k)//key Is:jason Key Is:hadoopTen  One}

Functional programming: Methods No side effects are important ideas for functional style programming, and the calculation and return of values should be the sole purpose of the method.

1. Less coupling between methods, more reliable and easier to reuse

2. (In a static type language) the parameters and return values of the method are checked by the inspector, so it is easier to infer the implied logic error based on the type error

4. Operation of the file: static methods in the source class

1 def dofile () {23     // by Scala.io.Source Object 4     Val file = Source.fromfile ("E:\\java_workspase\\scalaprogramworkspace\\test.txt")5      for (Line <- file.getlines ()) println (line) 6 7   }

Original Scala Learning: tuple,array,map, file manipulation