local-variables

问题 Each slot of local variable array is of 4-bytes. So to store a character, short or byte variables one slot is used. Means all smaller data-types internally gets converted into int data type. My doubt is: 1). Is it not making smaller data types useless, if internally they are of 4-bytes?, If yes, Why not remove such data-types from the language? 2). If each slot is of 1-byte then there will be no wastage of memory. Why not each slot is of 1-byte? 回答1: 1). Is it not making smaller data types

问题 How can I use a table variable while executing a command string? DECLARE @FileIDs TABLE ( File_ID int ) insert into @FileIDs select ID from Files where Name like '%bla%'; DECLARE @testquery as varchar(max); set @testquery = 'select * from @FileIDs'; exec(@testquery); returns the following error Msg 1087, Level 15, State 2, Line 1 Must declare the table variable "@FileIDs". 回答1: The table @FileIDs is not in the scope of exec(@testquery) . That's why you have that problem. To solve this problem

问题 In the following code (copied from Java Concurrency in Practice Chapter 2, section 2.5, Listing 2.8): @ThreadSafe public class CachedFactorizer implements Servlet { @GuardedBy("this") private BigInteger lastNumber; @GuardedBy("this") private BigInteger[] lastFactors; @GuardedBy("this") private long hits; @GuardedBy("this") private long cacheHits; public synchronized long getHits() { return hits; } public synchronized double getCacheHitRatio() { return (double) cacheHits / (double) hits; }

问题 In the following code (copied from Java Concurrency in Practice Chapter 2, section 2.5, Listing 2.8): @ThreadSafe public class CachedFactorizer implements Servlet { @GuardedBy("this") private BigInteger lastNumber; @GuardedBy("this") private BigInteger[] lastFactors; @GuardedBy("this") private long hits; @GuardedBy("this") private long cacheHits; public synchronized long getHits() { return hits; } public synchronized double getCacheHitRatio() { return (double) cacheHits / (double) hits; }

问题 So starting in Java 9, we can use var to declare local variables: var s = "cool"; is there a way to use a similar construct when declaring fields? class Container { final var s = "cool"; // does not compile tmk } doesn't seem like it from what I can tell. 回答1: is there a way to use a similar construct when declaring fields? No. According to JEP 286: Local-Variable Type Inference: This treatment would be restricted to local variables with initializers, indexes in the enhanced for-loop, and

问题 class C end var = "I am a local var outside" C.class_eval do def self.a_class_method puts var end end I know, this is not correct, because the def created a new scope. I also know that use define_method can create a instance method without creating a new scope, but my point is how to define a class method . 回答1: Class methods don't really exist in Ruby, they are just singleton methods of the class object. Singleton methods don't really exist, either, they are just ordinary instance methods of

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 I was expecting the following snippet: var = "Not Empty" unless defined? var var # => nil to return "Not Empty" , but I got nil . Any insight into why this is happening? 回答1: This is one of the only moments in Ruby I would call actual WTFs. You have to use unless defined? var var = :value end With the postfix syntax, the interpreter will internally nil -ify the value so it can reason about the variable, thus making it defined before the check is done: # Doesn't print anything unless defined?

问题 I was expecting the following snippet: var = "Not Empty" unless defined? var var # => nil to return "Not Empty" , but I got nil . Any insight into why this is happening? 回答1: This is one of the only moments in Ruby I would call actual WTFs. You have to use unless defined? var var = :value end With the postfix syntax, the interpreter will internally nil -ify the value so it can reason about the variable, thus making it defined before the check is done: # Doesn't print anything unless defined?

问题 This question already has answers here : Javascript function scoping and hoisting (16 answers) Closed 5 years ago . why does the following code segment generate the following output? code segment: var a = 10; function(){ console.log(a); var a = 5; } output: undefined 回答1: Because variable is hoisted at top and in your function you have declared the variable var a = 5 which is same as following: var a = 10; function(){ var a; // a = undefined console.log(a);//a is not defined so outputs