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可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: In JavaScript, the following gives an error: { __proto__: [] } instanceof Array; If I surround it in (brackets) it has no error: ({ __proto__: [] } instanceof Array); Why is this? 回答1: When the interpreter sees a { , by default, it will think that you're declaring a new block, such as { console.log('foo'); } As a result: { __proto__: [] } instanceof Array doesn't make much sense - you can't instanceof a block. But when it's wrapped in parentheses, the interpreter knows to expect a value inside the parentheses, not a block - so it evaluates

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I've written a MnemonicsBuilder class for JLabels and AbstractButtons. I would like to write a convenience method setMnemonics( JFrame f ) that will iterate through every child of the JFrame and select out the JLabels and AbstractButtons. How can I obtain access to everything contained in the JFrame? I've tried: LinkedList<JLabel> harvestJLabels( Container c, LinkedList<JLabel> l ) { Component[] components = c.getComponents(); for( Component com : components ) { if( com instanceof JLabel ) { l.add( (JLabel) com ); } else if( com instanceof

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am using the following code to removes childs on every viewgroup: protected void onDestroy() { super.onDestroy(); this.liberarMemoria(); } public void liberarMemoria(){ imagenes.recycleBitmaps(); this.unbindDrawables(findViewById(R.id.RelativeLayout1)); System.gc(); } private void unbindDrawables(View view) { if (view.getBackground() != null) { view.getBackground().setCallback(null); } if (view instanceof ViewGroup) { for (int i = 0; i < ((ViewGroup) view).getChildCount(); i++) { unbindDrawables(((ViewGroup) view).getChildAt(i)); } (

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: It seems my Android Studio does not want to break on any exception by default. Enabling break on "Any Exception" starts breaking within actual JDE libraries. Is there any way to force it to break only on exceptions within my code only? Coming from Visual Studio universe, looking for the default VS debug behavior here. 回答1: To break on all exceptions, caught or uncaught: Open the Breakpoints window via Run -> View Breakpoints . The Breakpoints dialog appears. In the left pane, scroll to the bottom. Select Any exception under Java Exception

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: The following compiles fine: Object o = new Object(); System.out.println(o instanceof Cloneable); But this doesn't: String s = new String(); System.out.println(s instanceof Cloneable); A compiler error is thrown. What is the problem? 回答1: A more blatant incarnation of your problem is the following: if ("foo" instanceof Number) // "Incompatible conditional operand types String and Number" This is specified in JLS 15.20.2 Type comparison operator instanceof : RelationalExpression: RelationalExpression instanceof ReferenceType If a cast of the

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am using Google Volley on the Android platform. I am having a problem in which the error parameter in onErrorResponse is returning a null networkResponse For the RESTful API I am using, I need to determine the Http Status Code which is often arriving as 401 (SC_UNAUTHORIZED) or 500 (SC_INTERNAL_SERVER_ERROR), and I can occasionally check via: final int httpStatusCode = error.networkResponse.statusCode; if(networkResponse == HttpStatus.SC_UNAUTHORIZED) { // Http status code 401: Unauthorized. } This throws a NullPointerException because

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Possible Duplicate: How do you determine equality for two JavaScript objects? Object comparison in JavaScript If I have two arrays or objects and want to compare them, such as object1 = [ { shoes: [ 'loafer', 'penny' ] }, { beers: [ 'budweiser', 'busch' ] } ] object2 = [ { shoes: [ 'loafer', 'penny' ] }, { beers: [ 'budweiser', 'busch' ] } ] object1 == object2 // false this can be annoying if you're getting a response from a server and trying to see if it's changed 回答1: Update: In response to the comments and worries surrounding the original

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: In an Android app, I added this code to onCreate() Closeable sss = new Socket(); if (!(sss instanceof Closeable)) { throw new RuntimeException("Something unexpected happened"); } The imports are: import java.io.Closeable; import java.net.Socket; The code compiles, but I am getting the exception: E/AndroidRuntime( 8293): java.lang.RuntimeException: Unable to start activity...: java.lang.RuntimeException: Something unexpected happened ... E/AndroidRuntime( 8293): Caused by: java.lang.RuntimeException: Something unexpected happened ... In a

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have a question of using switch case for instanceof object: For example: my problem can be reproduced in Java: if(this instanceof A) doA(); else if(this instanceof B) doB(); else if(this instanceof C) doC(): How would it be implemented using switch...case ? 回答1: This is a typical scenario where subtype polymorphism helps. Do the following interface I { void do(); } class A implements I { void do() { doA() } ... } class B implements I { void do() { doB() } ... } class C implements I { void do() { doC() } ... } Then you can simply call do()