instance-initializers

How to use an instance initializer with a generic HashMap?

由 喜你入骨 提交于 2019-12-13 04:39:22
问题 Can you use an instance initializer with a generic HashMap? I found this code online, but am having trouble converting it to a generic HashMap instead of a basic HashMap: someMethodThatTakesAHashMap(new HashMap(){{put("a","value-a"); put("c","value-c");}}); 回答1: Here's how: class Foo { static void someMethodThatTakesAHashMap(HashMap<String, String> map) { System.out.println(map); } public static void main(String[] args) { someMethodThatTakesAHashMap(new HashMap<String, String>(){{put("a",

Understanding this warning: The serializable class does not declare a static final serialVersionUID

由 时光总嘲笑我的痴心妄想 提交于 2019-12-12 09:29:05
问题 I have some static initializer code: someMethodThatTakesAHashMap(new HashMap<K, V>() { { put("a","value-a"); put("c","value-c");} }); For some reason I am receiving a warning from Eclipse: The serializable class does not declare a static final serialVersionUID. Is this complaining about the anonymous class? What can I do about that, or should I just suppress it. 回答1: The syntax you're using is called double-brace initialization - which is actually an "instance initialization block that is

Understanding this warning: The serializable class does not declare a static final serialVersionUID

由 别来无恙 提交于 2019-12-04 22:28:27
I have some static initializer code: someMethodThatTakesAHashMap(new HashMap<K, V>() { { put("a","value-a"); put("c","value-c");} }); For some reason I am receiving a warning from Eclipse: The serializable class does not declare a static final serialVersionUID. Is this complaining about the anonymous class? What can I do about that, or should I just suppress it. Pascal Thivent The syntax you're using is called double-brace initialization - which is actually an " instance initialization block that is part of an anonymous inner class " (certainly not a hack). So, when using this notation, you

Why can my instance initializer block reference a field before it is declared?

由 倖福魔咒の 提交于 2019-12-01 16:02:20
问题 My understanding is that you cannot reference a variable before it has been declared, and that all code (including instance initializers) that is within the body of a class, but outside of any method, is executed in order before constructor when the object is created (the exception being static variables and initializer blocks, which are run in order at the beginning of the program, to initialize the entire class). Why, then, does the following code compile (and run!): public class
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