initialization-block

来源： https://stackoverflow.com/questions/55356837/what-is-the-difference-between-init-block-and-constructor-in-kotlin

来源： https://stackoverflow.com/questions/55356837/what-is-the-difference-between-init-block-and-constructor-in-kotlin

来源： https://stackoverflow.com/questions/55356837/what-is-the-difference-between-init-block-and-constructor-in-kotlin

问题 I'm getting confused about when the instance initialization block should run. According to Kathy Sierra's book: Instance init blocks run every time a class instance is created So, consider having two classes: a parent and a child, according to this question and java's documentation: instantiating a subclass object creates only 1 object of the subclass type, but invokes the constructors of all of its superclasses. According to the above: why does the instance initialization block located in

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Static Initialization Blocks Consider the following code : public class Test { { System.out.println(\"Empty block\"); } static { System.out.println(\"Static block\"); } public static void main(String[] args) { Test t = new Test(); } } We understand that first the static block would be executed followed by the empty block. But the problem is that I have never been able to understand the real utility of an empty

问题 So I\'ve been brushing up on my Java skills as of late and have found a few bits of functionality that I didn\'t know about previously. Static and Instance Initializers are two such techniques. My question is when would one use an initializer instead of including the code in a constructor? I\'ve thought of a couple obvious possibilities: static/instance initializers can be used to set the value of \"final\" static/instance variables whereas a constructor cannot static initializers can be used

问题 We can put code in a constructor or a method or an initialization block. What is the use of initialization block? Is it necessary that every java program must have it? 回答1: First of all, there are two types of initialization blocks: instance initialization blocks , and static initialization blocks . This code should illustrate the use of them and in which order they are executed: public class Test { static int staticVariable; int nonStaticVariable; // Static initialization block: // Runs once

问题 As far as I understood the \"static initialization block\" is used to set values of static field if it cannot be done in one line. But I do not understand why we need a special block for that. For example we declare a field as static (without a value assignment). And then write several lines of the code which generate and assign a value to the above declared static field. Why do we need this lines in a special block like: static {...} ? 回答1: The non-static block: { // Do Something... } Gets