static-initializer

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 I\'m using a static code block to initialize some controllers in a registry I have. My question is therefore, can I guarantee that this static code block will only absolutely be called once when the class is first loaded? I understand I cannot guarantee when this code block will be called, I\'m guessing its when the Classloader first loads it. I realize I could synchronize on the class in the static code block, but my guess is this is actually what happens anyway? Simple code example would be

问题 Say a project contains several classes, each of which has a static initializer block. In what order do those blocks run? I know that within a class, such blocks are run in the order they appear in the code. I\'ve read that it\'s the same across classes, but some sample code I wrote disagrees with that. I used this code: package pkg; public class LoadTest { public static void main(String[] args) { System.out.println(\"START\"); new Child(); System.out.println(\"END\"); } } class Parent extends

问题 My question is about one particular usage of static keyword. It is possible to use static keyword to cover a code block within a class which does not belong to any function. For example following code compiles: public class Test { private static final int a; static { a = 5; doSomething(a); } private static int doSomething(int x) { return (x+5); } } If you remove the static keyword it complains because the variable a is final . However it is possible to remove both final and static keywords