临时函数,各种匿名函数使用
// All examples create a function object that performs upper-casing.
// So it's a function from String to String
val upperCase1: (String) -> String = { str: String -> str.toUpperCase() } // 1
val upperCase2: (String) -> String = { str -> str.toUpperCase() } // 2
val upperCase3 = { str: String -> str.toUpperCase() } // 3
// val upperCase4 = { str -> str.toUpperCase() } // 4
val upperCase5: (String) -> String = { it.toUpperCase() } // 5
val upperCase6: (String) -> String = String::toUpperCase // 6
println(upperCase1("hello"))
println(upperCase2("hello"))
println(upperCase3("hello"))
println(upperCase5("hello"))
println(upperCase6("hello"))