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Flashcard 149627104

Tags

#bloch-effective-java-2ed #java #java-generics

Question

Give an example how type safety could be compromised if it was legal to create arrays of parametrized types (but it is not legal).

Answer

You could create an array of lists of strings:
List<String>[] stringLists = new List<String>[1]; // this part is not legal and wouldn't compile
Because arrays are covariant, you can store the array into a variable of Object[] type and then store an element of type List<Integer> (or really List<anything>) as an element of the original array without causing ArrayStoreException because at runtime List<String> and List<Integer> are simply lists
So, we are in trouble - List<Integer> is stored where the compiler thought it was List<String>

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Annotation 149630585

Sherman

status	not read	reprioritisations
last reprioritisation on		suggested re-reading day
started reading on		finished reading on

John Sherman Cooper - Wikipedia, the free encyclopedia
Yale University Harvard Law SchoolProfessionLawyerReligionBaptistSignatureMilitary serviceService/branchUnited States ArmyYears of service1942–1946RankCaptainUnit15th Corps, U.S. Third ArmyBattles/warsWorld War IIAwardsBronze Star Medal John <span>Sherman Cooper (August 23, 1901 – February 21, 1991) was a politician, jurist, and diplomat from the U.S. state of Kentucky. He served three non-consecutive, partial terms in the United States S

Flashcard 149630657

Tags

#odersky-programming-in-scala-2ed #scala

Question

How to change it to exclude upper bound 4?


for (i <- 1 to 4)
  println("Iteration "+ i)

Answer

Use until method instead of to method:


for (i <- 1 until 4)
  println("Iteration "+ i)

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Flashcard 149630676

Tags

#odersky-programming-in-scala-2ed #scala

Question

How to move the condition to the generator in the loop?


for (file <- filesHere)
  if (file.getName.endsWith(".scala"))
    println(file)

Answer


for (file <- filesHere if file.getName.endsWith(".scala"))
  println(file)

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Flashcard 149630687

Tags

#odersky-programming-in-scala-2ed #scala

Question

What happens if you put multiple <- clauses in for?

Answer

You will get nested loops.

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Flashcard 149630698

Tags

#odersky-programming-in-scala-2ed #scala

Question

How can you reduce number of semicolons in for loop?

Answer

Use curly braces instead of parentheses - Scala compiler will not infer semicolons in parentheses.

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Flashcard 149630709

Tags

#odersky-programming-in-scala-2ed #scala

Question

How to introduce a val like variable mid-stream into for clauses?

Answer

Simply x=<whatever>, like val x=<whatever> elsewhere in the code, but without val keyword.

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Flashcard 149630720

Tags

#odersky-programming-in-scala-2ed #scala

Question

What form of for produces a new collection?

Answer

for clauses yield body

Keyword yield makes body compute elements of the new collection.

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Annotation 149630740

#odersky-programming-in-scala-2ed #scala

One difference from Java that you’ll quickly notice in Scala is that unlike Java, Scala does not require you to catch checked exceptions, or declare them in a throws clause.

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Flashcard 149630747

Tags

#odersky-programming-in-scala-2ed #scala

Question

What will calling f() return?


def f(): Int = try { return 1 } finally { return 2 }

Answer

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Flashcard 149630762

Tags

#odersky-programming-in-scala-2ed #scala

Question

What will calling g() return?

def g(): Int = try { 1 } finally { 2 }

Answer

status	not learned	measured difficulty	37% [default]	last interval [days]
repetition number in this series	0	memorised on		scheduled repetition
scheduled repetition interval		last repetition or drill

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Edited, memorised or added to reading queue

on 23-Aug-2014 (Sat)

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