casting

来源： https://stackoverflow.com/questions/1537358/is-there-ever-an-excuse-for-throwing-an-exception-from-an-implicit-conversion

来源： https://stackoverflow.com/questions/13851292/casting-between-number-types-in-golang

来源： https://stackoverflow.com/questions/54520085/why-are-iterator-items-which-are-references-not-cast-to-a-trait-object-reference

来源： https://stackoverflow.com/questions/54520085/why-are-iterator-items-which-are-references-not-cast-to-a-trait-object-reference

来源： https://stackoverflow.com/questions/27284910/create-big-integer-from-the-big-end-of-a-uuid-in-postgresql

问题 This question already has answers here : What's the difference between <?> and <? extends Object> in Java Generics? (3 answers) Closed 5 years ago . In Java generics, What is the advantage of using class GenericStack<T extends Object> {} over class GenericStack<T>{} . I have implemented a generic stack using both of the above approaches but unable to trace out the difference. Help me to understand this. 回答1: There's no difference. <T> and <T extends Object> are equivalent. 来源： https:/

问题 This question already has answers here : What's the difference between <?> and <? extends Object> in Java Generics? (3 answers) Closed 5 years ago . In Java generics, What is the advantage of using class GenericStack<T extends Object> {} over class GenericStack<T>{} . I have implemented a generic stack using both of the above approaches but unable to trace out the difference. Help me to understand this. 回答1: There's no difference. <T> and <T extends Object> are equivalent. 来源： https:/

问题 This question already has answers here : Is there a way to convert integers to bools in go or vice versa? (6 answers) Closed 4 years ago . bitSet := true var bitSetVar int8 How can I assign bitSet to bitSetVar as 1 I can do this: if bitSet { bitSetVar = 1 } else { bitSetVar = 0 } Is this the best way? 回答1: Because the zero value for a int8 is 0 , the else branch is not necessary. bitSet := true var bitSetVar int8 if bitSet { bitSetVar = 1 } There are no conversions from bool to integer types.

问题 This question already has answers here : Rails Migrations: tried to change the type of column from string to integer (6 answers) Closed 5 years ago . I am using the following query to change the data type of a column from text to integer but getting error: alter table a.attend alter column terminal TYPE INTEGER ; ERROR: column "terminal" cannot be cast automatically to type integer 回答1: create table test(id varchar ); insert into test values('1'); insert into test values('11'); insert into

问题 In Java, I can write code like: void cast(A a) { if(a instanceof Person) { Person p = (Person) a; } } In Kotlin, what should I do? Use as operator or is operator? 回答1: is X is the equivalent of instanceof X foo as X is the equivalent of ((X) foo) Additionally, Kotlin performs smart casting where possible, so no additional cast needed after you check the type using is : open class Person : A() { val foo: Int = 42 } open class A and then: if (p is Person) { println(p.foo) // look, no cast