constructor

问题 In Java, Why am I getting this error: Error: The constructor WeightIn() is undefined Java Code: public class WeightIn{ private double weight; private double height; public WeightIn (double weightIn, double heightIn){ weight = weightIn; height = heightIn; } public void setWeight(double weightIn){ weight = weightIn; } public void setHeight(double heightIn){ height = heightIn; } } public class WeightInApp{ public static void main (String [] args){ WeightIn weight1 = new WeightIn(); //Error

问题 Here is an extract from item 56 of the book "C++ Gotchas": It's not uncommon to see a simple initialization of a Y object written any of three different ways, as if they were equivalent. Y a( 1066 ); Y b = Y(1066); Y c = 1066; In point of fact, all three of these initializations will probably result in the same object code being generated, but they're not equivalent. The initialization of a is known as a direct initialization, and it does precisely what one might expect. The initialization is

问题 Please help to understand why does the following code public class HeapQn1 { /** * @param args */ public HeapQn1() { new HeapQn1(); } static HeapQn1 n = new HeapQn1(); public static void main(String[] args) { } } results in java.lang.StackOverflowError at com.rg.test.interview.HeapQn1.<init>(HeapQn1.java:8) at com.rg.test.interview.HeapQn1.<init>(HeapQn1.java:9) ... As per my understanding the memory allocation for an object happens in the heap memory and I was expecting an OutOfMemoryError

问题 Lately I've been wondering if there's a difference between initializing the variables that have a default value on the Constructor VS on the class definition. Which one is better, taking into consideration the optimization: class TestClass { private $test_var = 'Default Value'; function __construct() { } } class TestClass2 { private $test_var; function __construct() { $this->test_var = 'Default Value'; } } 回答1: The advantage of initializing properties outside of the constructor is that

问题 EF has generated for me some partial classes, each with a constructor, but it says not to touch them (example below), now if I make my own secondary partial class and I want to have a constructor that automatically sets some of the fields how do I do so as it would conflict? //------------------------------------------------------------------------------ // <auto-generated> // This code was generated from a template. // // Manual changes to this file may cause unexpected behavior in your

问题 I definitely remember seeing somewhere an example of doing so using reflection or something. It was something that had to do with SqlParameterCollection which is not creatable by a user (if I'm not mistaken). Unfortunately cannot find it any longer. Can anyone please share this trick here? Not that I consider it a valid approach in development, I'm just very interested in the possibility of doing this. 回答1: // the types of the constructor parameters, in order // use an empty Type[] array if

问题 I definitely remember seeing somewhere an example of doing so using reflection or something. It was something that had to do with SqlParameterCollection which is not creatable by a user (if I'm not mistaken). Unfortunately cannot find it any longer. Can anyone please share this trick here? Not that I consider it a valid approach in development, I'm just very interested in the possibility of doing this. 回答1: // the types of the constructor parameters, in order // use an empty Type[] array if

问题 I get this error message, when I open a closed App again via App-Change button: Caused by: java.lang.InstantiationException: can't instantiate class com.*.FragmentContact$1; no empty constructor I've found several tips about Inner-Classes and to make them static etc. But this FragmentContact is a public class in a *.java-file and has a public empty constructor . I'm using Google Maps Api v2 in this project and do a trick somewhere from the internet to setup my MapView. Look here: @Override

问题 Is it possible to override the constructor of the base class in the derived class? If so, the how can it be accomplished and in what use case would this be practical? If not, why not? 回答1: No, you can't override constructors. The concept makes no sense in C#, because constructors simply aren't invoked polymorphically. You always state which class you're trying to construct, and the arguments to the constructor. Constructors aren't inherited at all - but all constructors from a derived class

问题 I get this error message, when I open a closed App again via App-Change button: Caused by: java.lang.InstantiationException: can't instantiate class com.*.FragmentContact$1; no empty constructor I've found several tips about Inner-Classes and to make them static etc. But this FragmentContact is a public class in a *.java-file and has a public empty constructor . I'm using Google Maps Api v2 in this project and do a trick somewhere from the internet to setup my MapView. Look here: @Override