![No “static” in Scala
Scala: Java:
object PersonUtil { public class PersonUtil {
val AgeLimit = 18 public static final int
AGE_LIMIT = 18;
def countPersons(persons:
List[Person]) = ... public static int
countPersons(List<Person>
}
persons) {
...
}
}](https://image.slidesharecdn.com/1-2-scalabasics-120331150303-phpapp01/85/1-2-scala-basics-10-320.jpg)
![Varargs
def foo(values: String*){ } public void foo(String... values){ }
foo("bar", "baz") foo("bar", "baz");
val arr = Array("bar", "baz") String[] arr = new String[]{"bar",
foo(arr: _*) "baz"}
foo(arr);](https://image.slidesharecdn.com/1-2-scalabasics-120331150303-phpapp01/85/1-2-scala-basics-15-320.jpg)
![Generics
Scala: Java:
List[String] List<String>](https://image.slidesharecdn.com/1-2-scalabasics-120331150303-phpapp01/85/1-2-scala-basics-19-320.jpg)
![Tuples
Scala: Java:
val tuple: Tuple2[Int, String] = Pair<Integer, String> tuple = new
Pair<Integer, String>(1, “apple”)
(1, “apple”)
val quadruple =
... yeah right... ;-)
(2, “orange”, 0.5d, false)](https://image.slidesharecdn.com/1-2-scalabasics-120331150303-phpapp01/85/1-2-scala-basics-20-320.jpg)
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1.2 scala basics
- 1. Scala basics
- 2. ;
- 3. Type definitions Scala Java s: String String s i: Int int i / Integer i
- 4. Variables Scala: Java: val s = “Hello World” public final String s = “Hello World”; var i = 1 public int i = 1; private var j = 3 private int j = 3;
- 5. Methods Scala: Java: def add(x: Int, y: Int): Int = { public int add(int x, int y) { x+y return x + y; } } def add(x: Int, y: Int) = x + y def doSomething(text: String) { public void doSometing(String text) { } }
- 6. Methods (2) Scala: Java: myObject.myMethod(1) myObject.myMethod(1); myObject myMethod(1) myObject myMethod 1 myObject.myOtherMethod(1, 2) myObject.myOtherMethod(1, 2); myObject myOtherMethod(1, 2) myObject.myMutatingMethod() myObject.myMutatingMethod() myObject.myMutatingMethod myObject myMutatingMethod
- 7. Methods (3) Scala: Java: override def toString = ... @Override public String toString() {...}
- 8. Classes and constructors Scala: Java: class Person(val name: String) public class Person { private final String name; public Person(String name) { this.name = name; } public String getName() { return name; } }
- 9. Traits (= Interface + Mixin) Scala: Java: trait Shape { interface Shape { def area: Double public double area(); } } class Circle extends Object with public class Circle extends Object Shape implements Shape
- 10. No “static” in Scala Scala: Java: object PersonUtil { public class PersonUtil { val AgeLimit = 18 public static final int AGE_LIMIT = 18; def countPersons(persons: List[Person]) = ... public static int countPersons(List<Person> } persons) { ... } }
- 11. if-then-else Scala: Java: if (foo) { if (foo) { ... ... } else if (bar) { } else if (bar) { ... ... } else { } else { ... ... } }
- 12. For-loops Scala: Java: for (i <- 0 to 3) { for (int i = 0; i < 4; i++) { ... ... } } for (s <- args) println(s) for (String s : args) { System.out.println(s); }
- 13. While-loops Scala: Java: while (true) { while (true) { ... ... } }
- 14. Exceptions Scala: Java: throw new Exception(“...”) throw new Exception(“...”) try { try { } catch { } catch (IOException e) { case e: IOException => ... ... } finally { } finally { } }
- 15. Varargs def foo(values: String*){ } public void foo(String... values){ } foo("bar", "baz") foo("bar", "baz"); val arr = Array("bar", "baz") String[] arr = new String[]{"bar", foo(arr: _*) "baz"} foo(arr);
- 16. (Almost) everything is an expression val res = if (foo) x else y val res = for (i <- 1 to 10) yield i // List(1, ..., 10) val res = try { x } catch { ...; y } finally { } // x or y
- 17. Collections – List Scala: Java: val numbers = List(1, 2, 3) List<Integer> numbers = new ArrayList<Integer>(); val numbers = 1 :: 2 :: 3 :: Nil numbers.add(1); numbers.add(2); numbers.add(3); numbers(0) numbers.get(0); => 1 => 1
- 18. Collections – Map Scala: Java: var m = Map(1 -> “apple”) Map<Int, String> m = m += 2 -> “orange” new HashMap<Int, String>(); m.put(1, “apple”); m.put(2, “orange”); m(1) m.get(1); => “apple” => apple
- 19. Generics Scala: Java: List[String] List<String>
- 20. Tuples Scala: Java: val tuple: Tuple2[Int, String] = Pair<Integer, String> tuple = new Pair<Integer, String>(1, “apple”) (1, “apple”) val quadruple = ... yeah right... ;-) (2, “orange”, 0.5d, false)
- 21. Packages Scala: Java: package mypackage package mypackage; ... ...
- 22. Imports Scala: Java: import java.util.{List, ArrayList} import java.util.List import java.util.ArrayList import java.io._ import java.io.* import java.sql.{Date => SDate} ???
- 23. Nice to know Scala: Java: Console.println(“Hello”) System.out.println(“Hello”); println(“Hello”) val line = Console.readLine() BufferedReader r = new BufferedReader(new val line = readLine() InputStreamRead(System.in) String line = r.readLine(); error(“Bad”) throw new RuntimeException(“Bad”) 1+1 new Integer(1).toInt() + new Integer(1).toInt(); 1 .+(1) 1 == new Object new Integer(1).equals(new Object()); 1 eq new Object new Integer(1) == new Object(); """Asregex""".r java.util.regex.Pattern.compile(“Asregex”);