require vs assert

require

• predifined function
• if require is false, throw IllegalArgumentException

class Rational(x: Int, y: Int) {
    require(y>0, "denominator must be positive")
} 

val errorValue = new Rational(1,0) 
// java.lang.IllegalArgumentException: requirement failed: denominator must be positive
// ...

assert

• if assert is false, throw AssertionError

val a = sqrt(y)
assert(x>=0)

difference

• requireis used to enforce a precondition on the caller of a function.

  • function을 부를 때, 컨디션 체크.
  • Excetion 메시지에서도 볼 수 있듯, argument가 잘못된 것.
  • (비유) HTTP로 따지자면.. 400 bad request

• assert is used as to check the code of the function itself.

  • function에서 온 값을 비교

  • (비유) HTTP로 따지자면.. 500 internal server error