final

问题 Is the any difference in performance and/or any other benefits we can get when using final keyword with constant utility class. [ This class contains only static final fields and private constructor to avoid object creation] public class ActionConstants { private ActionConstants() // Prevents instantiation { } public static final String VALIDFIRSTLASTNAME = "[A-Za-z0-9.\\s]+"; public static final String VALIDPHONENUMBER = "\\d{10}"; ... ... } Only diffrence is class is made final public final

问题 Is the any difference in performance and/or any other benefits we can get when using final keyword with constant utility class. [ This class contains only static final fields and private constructor to avoid object creation] public class ActionConstants { private ActionConstants() // Prevents instantiation { } public static final String VALIDFIRSTLASTNAME = "[A-Za-z0-9.\\s]+"; public static final String VALIDPHONENUMBER = "\\d{10}"; ... ... } Only diffrence is class is made final public final

问题 I have a final class Ring defined as: final class Ring { public static final int OUT = 3; public static final int MID = 2; public static final int IN = 1; } I also have a public class MorrisBoard with the following code: public class MorrisBoard { public static final Ring RING = new Ring(); private boolean checkMillBy(int ring, int x, int y) { switch(ring) { case MorrisBoard.RING.OUT: //... case MorrisBoard.RING.MID: //etc. //... } return false; } MorrisBoard.RING.OUT references a variable

问题 This is a follow-up question to my previous initialization variable question. Suppose we're dealing with this context: object AppProperties { private var mgr: FileManager = _ def init(config: Config) = { mgr = makeFileManager(config) } } The problem with this code is that any other method in AppProperties might reassign mgr . Is there a technique to better encapsulate mgr so that it feels like a val for the other methods? I've thought about something like this (inspired by this answer):

问题 Does class file format provide support for final keyword in case of using it with variables? Or does it just deduce the effective finality of a variable from code and JIT compiler perform optimization based on it? Here, in class file format documentation, they mentioned about final keyword, but only in case of using it with final block and final class . There is nothing about final variables . 回答1: No, there is no such information encoded in class file. You may easily verify this by compiling

问题 This question already has answers here : Why can final object be modified? (7 answers) Closed 5 years ago . What does it mean for a collection to be declared final in Java? Is it that no more elements can be added to it? Is it that the elements already there cannot be changed? Is it something else? 回答1: No. It simply means that the reference cannot be changed. final List list = new LinkedList(); .... list.add(someObject); //okay list.remove(someObject); //okay list = new LinkedList(); //not

问题 I've got this error while trying to use a local member of one class in inner class inside. I know that declare it as final will solve the issue but I read that Java 8 should handle it automaticlly, I'm using Intellij with Java 8 and it still does not compile. Is there any other way to fix it without declare it as final? thanks. 回答1: I know that declare it as final will solve the issue but I read that Java 8 should handle it automatically. Java 8 will handle it if the variable is effectively

问题 I've got this error while trying to use a local member of one class in inner class inside. I know that declare it as final will solve the issue but I read that Java 8 should handle it automaticlly, I'm using Intellij with Java 8 and it still does not compile. Is there any other way to fix it without declare it as final? thanks. 回答1: I know that declare it as final will solve the issue but I read that Java 8 should handle it automatically. Java 8 will handle it if the variable is effectively

问题 I asked this question before but I didn't get an appropriate answer. How can non-final fields be used in a anonymous class class if their value can change? class Foo{ private int i; void bar(){ i = 10 Runnable runnable = new Runnable (){ public void run (){ System.out.println(i); //works fine }//end method run }//end Runnable }//end method bar }//end class Foo If the local variables which are used inside an anonymous class must be final to enable the compiler inlining their values inside the

问题 When an object needs to be synchronized, the IDE complains if it's not set non-final (because its reference isn't persistent): private static Object myTable; .... synchronized(myTable){ //IDE complains! //access myTable here... } We all know the IDE complains to prevent another thread from entering the guarded block if the thread holding the lock changes the non-final object's references. But could a synchronized object's reference also be changed by another thread B while thread A holds the