static | 易学教程

Android java performance: invoking static method from self class or outer class

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问题 by an high-performance point of view, calling an outer class static method is slower than calling a static method in the same class? 回答1: No, never. Leaving method visibility apart, static method are just global function in the C sense. So it can't matter, what class they belong to, not even on Android. 回答2: It depends. Consider the following: public class Outer { /*private*/ static void outerMethod() { // do stuff } static class Inner { public void doStuff() { outerMethod(); } } } The

Overriding static members and “static static arrays”

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问题 I've got a tricky issue with "overriding" static arrays. I've got static arrays (for simplicity) that are of fixed length in different derived classes, but still all sizes are known in compile-time. I've also got a virtual function in the base class, but I don't know how to tackle the problem of overriding these arrays and array-sizes in the derived classes so that this virtual function works correctly, i.e. gives the sizes and array contents from the derived classes. Example: class B {

Compile static version of QT + OpenSSL Support

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问题 I have downloaded source files of qt-everywhere-opensource-src-5.8.0 from here: https://download.qt.io/snapshots/qt/5.8/5.8.0/latest_src/ I want to compile it with support for Static version of QT + OpenSSL I have installed QtFramework(qt-opensource-windows-x86-mingw530-5.8.0) and Win32 OpenSSL v1.0.2k downloaded from here: https://slproweb.com/products/Win32OpenSSL.html What arguments need? 来源： https://stackoverflow.com/questions/41938379/compile-static-version-of-qt-openssl-support

Pass JButton to Utility class. Acceptable?

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问题 I have a JFrame that does things. I have a JButton hidden from view in that JFrame. In a SwingWorker i have a utility Class such as checkNDownloadFile of which I pass a JButton to it. So it can make it visible/usable when the process completes. My question is, is this acceptable. I dont know of any other method to do this effect. (Keep in mind the checkNDownloadFile class is all static. Its only needed/ran once.) Sudo Code -----------------------------------------------------------------

一文让你理解Class类加载机制

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理解类加载机制 Class文件是各种编译器编译生成的二进制文件，在Class文件中描述了各种与该类相关的信息，但是Class文件本身是一个静态的东西，想要使用某个类的话，需要java虚拟机将该类对应的Class文件加载进虚拟机中之后才能进行运行和使用。举个例子，Class文件就好比是各个玩具设计商提供的设计方案，这些方案本身是不能直接给小朋友玩的，需要玩具生产商根据方案的相关信息制造出具体的玩具才可以给小朋友玩。那么不同的设计商有他们自己的设计思路，只要最终设计出来的方案符合生产商生产的要求即可。生产商在生产玩具时，首先会根据自己的生产标准对设计商提交来的方案进行阅读，审核，校验等一系列步骤，如果该方案符合生产标准，则会根据方案创建出对应的模具，当经销商需要某个玩具时，生产商则拿出对应的模具生产出具体的玩具，然后把玩具提交给经销商。对于java而言，虚拟机就是玩具生产商，设计商提交过来的方案就是一个个的Class文件，方案创建的模具就总的来说，类的加载过程，包括卸载在内的整个生命周期共有以下7个阶段：加载、验证、准备、初始化、卸载这5个阶段的顺序是确定的，但是解析阶段不一定，在某些情况下解析可以在初始化之后再执行，为了支持java的运行时绑定，也成为动态绑定或晚期绑定。invokedynamic指令就是用于动态语言支持，这里“动态

System.loadLibrary() returns exception from static block

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问题 I have created a Java app which loads one Windows DLL from the static initialization block. The code snippet is given below: // MyTestJava class starts class MyTestJava { static { System.loadLibrary("MyLib"); } } // MyTestJava class def ends here I heard that for kinds of library initializations performed from static block, JVM should search in java.library.path . So I set library path for JVM as follows and put MyLib.dll under c:\Libs folder. options[1].optionString = "-Djava.library.path=C:

How start an activity using Intent inside a inner static class?

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问题 I have a static and inner class inside my Activityclass . I need to call an Activity using Intent(context,nameOfTheNewActivity.class) because I am trying to call an Intent when an item from a RecyclerView.ViewHolder is clicked. I had to Override the onClick to get the position of the item was clicked using getLayoutPosition() (this getLayoutPosition() worked fine). Now when I try to use Intent I have the error: Non-static method cannot be referenced by a static context. I read another links

Issue starting activity from non-activity class

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问题 I am a noob to android and I have a Map Activity that also uses OverlayItems. Within the onButtonTap method of my overlay class, I want to execute startActivity so i can then use intent.ACTION_CALL. Intent callIntent = new Intent(Intent.ACTION_CALL); callIntent.setData(Uri.parse("tel:"+MapActivity.phonenumber0)); startActivity(callIntent); in the code above i am asked to create a method for startActivity(Intent), which I don't understand. and when i try... Intent callIntent = new Intent

Declaring arrays statically in Constants file

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问题 I'm declaring a number of static arrays in a Constants.m file, for example the numberOfRowsInSection count for my tableView: + (NSArray *)configSectionCount { static NSArray *_configSectionCount = nil; @synchronized(_configSectionCount) { if(_configSectionCount == nil) { _configSectionCount = [NSArray arrayWithObjects:[NSNumber numberWithInt:2], [NSNumber numberWithInt:2], [NSNumber numberWithInt:4], [NSNumber numberWithInt:3], [NSNumber numberWithInt:0], nil]; } return _configSectionCount; }

How do I call main method of one class inside another class?

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问题 I have a thread that, when the current application closes, must start the main() method of another class. I included ClassName.main(someStringArray) in the run() of the thread but the method wasn't called. What might have gone wrong? The Thread I defined : private class VideoCreator extends Thread{ public VideoCreator(){ pathToPass = savePath + "/" + "video.mov"; passVect.add("-w"); passVect.add("1280"); passVect.add("-h"); passVect.add("800"); passVect.add("-f"); passVect.add("25"); passVect