I can't really understand the purpose of using constructor. why not just replace the constructor with methods? Is it both are different. Pls anyone, do clear me on this. In a way, it is a method because of its format but is different: - it bears the same name of the class (since you will be using that constructor to instantiate ... |
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simplifying my problem: I am trying to send a String that the user has provided which has two parts (query and result) to the Question constructor IN ANOTHER CLASS This makes no sense. The Question c'tor is in the Question class. Do you mean these strings originate in one class, and then you're going go call a method in another class, ... |
public class Demo { public static void main(String args[]) { } public class Psp { public String genre; public String coolness; public int rating; public Psp() { genre = ""; coolness = ""; rating = 0; } public Psp(String genre, String coolness, int rating) { this.genre = genre; this.coolness = coolness; this.rating = rating; Psp[] newPspArray = new Psp[50]; newPspArray[0] = ... |
I suppose you can use reflection, but what's the point? The code isn't set in stone, is it? Just make certain that you declare the field in question by its ADT, and that the only part that you name a concrete class is when you instantiate it. Then you'll only have that one line of code to change later. |
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You don't have to provide any constructors for your class, but you must be careful when doing this. The compiler automatically provides a no-argument, default constructor for any class without constructors. This default constructor will call the no-argument constructor of the superclass. In this situation, the compiler will complain if the superclass doesn't have a no-argument constructor so you must verify ... |
Maybe I didn't express myself clearly. I know where I can find the InputStream constructors - but that's not what I'm looking for. I'm looking for ALL the classes that take e.g. an InputStream as a parameter. I know that InputStreamReader and BufferedInputStream have constructors that take an InputStream as a parameter - but how can I get a list of ... |
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CommissionEmployee4 constructor: base-salaried commission employee: Mark Sands social security number: 888-88-8888 gross sales: 8000.00 commission rate: 0.15 base salary: 0.00 BasePlusCommissionEmployee5 constructor: base-salaried commission employee: Mark Sands social security number: 888-88-8888 gross sales: 8000.00 commission rate: 0.15 base salary: 2000.00 ************************************************** ************** why the object employee2 print this statment---> (base salary: 0.00) i know that when we create the employee2 object:first ... |
Hi I am writing a program that contains two classes and a main driver. I am creating a "new Player" Class within the main driver but it keeps telling me it cannot find the constructor for player? I don't understand ? Why should it say this when the constructor has been built .? I am very new to this and have ... |
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This sounds too homework-ish and also you have an interesting posting history . But anyway: No, you are not on the right track. You need no main method yet, and the variables you defined must be instance variables of your class. Write a constructor that accepts three parameters and set these to the corresponding variables. Search a bit and you will ... |
Consider the code below. I am reffering to some books/tutorials which say Constructor for Apple is called once for each constant when variable ap is defined. But I don't see this happens actually,i.e. When I comment out the the forloop after line (Apple ap), I don't get the print message from the constructor of the apple, which according to theory should ... |
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what is wrong with you? add my code to the method i specified in your code. try to run it. SHOW US THE CODE and then SHOW US THE ERROR MESSAGE. dont tell us. dont whine. just copy and paste. no one is getting defensive or angry with you. its just when people are stubborn, lol, you have to talk loudly ... |
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The "applet" that appears outside the constructor is a field with the default protection (package access). I prefer the term "field" since it more easily differentiates from local variables, and it suggests an attribute of the class, that is, something that holds state. It's a bad practice to define fields as temporary place holders, and refering to them as "variables" muddies ... |
Ok, so as some of you have seen I'm very new to this. I want to make it so when I create an object the user has to enter a name, being a String, but I want it so it can only be 1-10 characters long, otherwise return a message. I can use the .length line fine if they are inputting ... |
this is part of my x-tra credit lab- The smiley face will have at least the following methods: Constructor, change position, change color, happyOrSad (changes its mouth and winks for happy, has a tear for sad), change size. Can I create the happy face in it's own method and call other methods? And also, what's a constructor? |
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This isn't a constructor at all, rather a new method called setTime() that changes the value of the stored time to some magic value you've set. The constructor is the declaration with the same name as the class. It can optionally take arguments, though the constructor you've already defined doesn't. Your new constructor needs the same arguments as the setNewTime() method. ... |
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Ok, I found this java swing validation package you can build online. I followed all the steps creating the classes and everything compiles. However, when I make the call to the constructor I still recieve "parent is not public in java.awt.Component; cannot be accessed from outside package.." I understand from earlier in this post that I'm trying to access something I'm ... |
So in the Child class Manager, I must use Super to access the Employee constructor? You don't have to explicitly call a super(...) c'tor, but if you don't, then it will implicitly call super(), the no-arg c'tor. If you go that route, then the parent class has to have such a c'tor. Now, whether you add that c'tor to the parent ... |
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I have a pretty basic question that I'm somewhat confused on. When creating constructors is it necessary, or good practice, to start with a default constructor that will initialize certain variables and then follow with an overloaded constructor that will allow the client to set the initial values? I haven't found clear guidance on this so I'm hoping somebody can provide ... |
In some scopes, two distinct identifiers with the same name can exist. There has to be some rule about which one takes precedence when there's no qualification. It's simpler if it's consistent and it's always the local. If it weren't, then a) it would be inconsistent, which would be confusing, and b) we'd need a new keyword or other mechanism to ... |
Hi, I am fairly new to java. I would like to know how a message could be sent from a new value I have set up ( Peak.setHeight(10)) to the constructor object reference aPeak. public class Test private Peak a; // Constructor public Test(Peak aPeak) { Peak = aPeak; } public void Height() { Peak.setHeight(10); } I know I could do ... |
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In case what you are comparing is default no arg constructors vs user defined constructors to initialize and object, and that in a default constructor case you plan to use the setter methods to impart a state to the object a good case would be to study mutable vs immutable to make the differences and semantics clear. Then we can discuss ... |
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I don't see it called here (other application?), but the "rules" state that if you don't write your own constructor, a default (no arg) constr will be written for you. If you do write one (with args, as you have) the no arg constr will NOT be written for you. Thus if you call a no arg contr in this later ... |
I am supposed to add this for an assignment: a. a private variable "double currentGPA" b. a constructor that initializes both "currentGPA" to "0.0" and "score" to "0" as the default values c. a constructor that initializes the variables "score: and "currentGPA" to the values assigned by callers. What is a caller in the program? Do I add another line that ... |
I am supposed to add this for an assignment: a. a private variable "double currentGPA" b. a constructor that initializes both "currentGPA" to "0.0" and "score" to "0" as the default values c. a constructor that initializes the variables "score: and "currentGPA" to the values assigned by callers. What is a caller in the program? Do I add another line that ... |
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/* Write a method that evaluates to true or false depending on whether a box completely fits inside another: public boolean nests( Box outsideBox ) This is potentially a difficult method, since the box may fit or not fit depending on how it is rotated. To simplify the method, write it so that it returns true if the two boxes nest ... |
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The design where you can have a constructor which provides a list of folders and a constructor which provides a list of files seems kind of questionable to me. What if you want to have both folders and files in your Folder object? Clearly the design allows for that. So I would just have one constructor where you pass in both ... |
Each constructor of a class must either a.) delegate to another constructor of the same class (using this(...)) or b.) call a constructor of the base class (using super(...)). If you do neither of both, then Java will try to call the argument-less super constructor by default (i.e. it's the same as if you wrote "super();" as the first line) Your ... |
java-noob-from-cpp wrote: I come from C++ and wonder how I can initialize members of subclasses before calling the parent constructor: That can't be done. Java enforces the rule that calling the super constructor is the first thing that's ever done in your constructor. This makes sure that the parent class properties are completely set up before any other code can access ... |
1. In your main method you should take input of names of 3 friends. not inside the constructorss. 2. then create three thread objects using those names. 3. If you dont know how to take input using JOptionPane see [this|http://www.java2s.com/Code/JavaAPI/javax.swing/JOptionPaneshowInputDialogObjectmessage.htm] 4. Then start the threads. 5. you are supposed to print some blank spaces be4 printing the name. use a loop ... |
You ignore all your constructor arguments so they can be removed. If can change my first name and last name, I wonder what is the use case for this. Nothing like money laundering I hope. I would suggest you - keep the first name and last name in the constructor and actually set the first and last name. - them final ... |
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I'm taking an online Computer Science AP course and its all about Java. I've done pretty good so far, but I have a question about constructors. My instructor encouraged me to use Google to help me with my assignments and various Java questions. I am supposed to write out the BigVic constructor that this needs. What exactly do I need to ... |
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System.out.println("Enter Arrow shaft name:"); name = input.nextLine() ; System.out.println("Enter SKU number:"); product = input.nextInt(); System.out.println("Enter number of units in stock:"); stock = input.nextInt(); System.out.println("Enter price per unit:"); price = input.nextDouble(); //create and initialize an Arrow object CarbonArrows A1 = new CarbonArrows(name, product, stock, price); // System.out.println("Manfacturer name is: " + A1.getname()); //System.out.println("The SKU number is: " + A1.getproductIn()); // System.out.println("The number ... |
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Becuase CircleTest does extend Circle, the CircleTest default constructor ( even though you have not tupplied one the compiler will) calls the super class default constructor. Now becuase you have supplied a non-default constructor in the super class the default constructor in Circle does not exist. This is the error you get. |
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Second of all, there's only one way to calculate area. The first method is it, but it should NOT take any arguments. It should return the value based on the width and height for that instance. Third, why getters and setters? I can see where Rect could be immutable. Why not ditch the setters? |
And for the record, Driver_Panel is not a desirable name for a class/constructor or method. Naming conventions dictate that the class should - in this case - be named DriverPanel - what is referred to as "Camel Case". And therefore so should the contructor (ctor for short) ... ... and that method names should not begin with an uppercase letter; therefore ... |
Hi, My code is : URL url = new URL("xxxxx/yyyy.jar"); DownloadServiceListener dsl = ds.getDefaultProgressWindow(); ds.loadResource(url, null, dsl); (This code works with javaws) After loading yyyy.jar file from a URL I want to instantiate a class file in this jar . This class contsructor's parameter is string . So, Class[] classdizi = new Class[1] ; classdizi[0] = String.class; Object[] argumanDizi = new ... |
Kevin, thanks for the suggestion, that's certainly a great solution. To me, it still makes more sense to put the checking code in the constructor with the lowest number of arguments, and this would work if not for the fact that you're limited by the way that you can call them. The only problem with working your way up is that ... |
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Just FYI, all primitive wrapper classes are final, so the isAssignableFrom doesn't cover any more bases than using equals(), as far as I can see. And it's a bit less self-documenting, since it would seem to imply (since in most cases, a.isAssignableFrom(b) checks to see whether a widening conversion from b to a is allowed) that calling your method with Short.class ... |
Hi, API Documentation for DecimalFormat class says. "In general, do not call the DecimalFormat constructors directly, since the NumberFormat factory methods may return subclasses other than DecimalFormat. If you need to customize the format object, do something like this: " What is the exact reason that we should not use constructor directly. Thanks, Chamal. |
#include using namespace std; class Base { public: char* name; void display() { cout << name << endl; } }; class Derived: public Base { public: char* name; void display() { cout << name << ", " << Base::name << endl; } }; int main() { Derived d; d.name = "Derived Class"; d.Base::name = "Base Class"; // call Derived::display() d.display(); ... |
hello folks i have a class that contains only static members and as a result don't want it to be possible to create instances of it. But if it is a top level class i cannot declare it static so even if i don't provide a constructor it will still be possible to create an instance of the class, can i ... |
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You need to create a new instance of your Abreviation class for each line you read from the file, so you can't read the file in the constructor. The constructor gets called for each instance of the class you create. I wouldn't recommend StringTokenizer here, unless it's specified in your project. There are various ways you could try. I suggest you ... |
**The class has the methods below.** **public String getName()** **public String getPosition()** **public double getRate()** **public double getHours()** **public void setName(String newName)** **public void getARaise(double inc)** **public void work(double time)** **public double getPaid()** **public boolean equals(HourlyEmployee other)** **public String toString()** **The first 4 methods return the name, the position, the rate** **and the hours, in this order.** **The method getARaise adds ... |
Hi...... You are doing two mistakes. 1. In Employee2 Class all varible that you are accesing are defind as private access spcifier. so these variable would not be accessible outside of class. Make it public or default or anything but not private. 2. You are accessing right side variable for printing content while you should access left hand side variables to ... |
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As an exercise, I'd like to write a rudimentary annotations-based resource injection scheme. I've been googling around, but I'm getting lots of hits on J2EE stuff, which is not what I need. So far I've read a little bit about class loaders, which would help me intercept class lookups, and a little bit about proxies, which seem like they would help ... |
1) confusing as the code is, I think Java is preventing you from creating a recursive call of the constructor with no arguments. 2) you have two calls to this(), the second this() call is breaking the rule of this() needing to be the first call in the constructor. It has nothing to do with a static method call. 3) yes, ... |
thats because month takes value between 0 and 11. For December you need to give 11 and not 12. Since you have given 12, the month has been set to 0 - that is, january and the year has been incremented. Edited by: Smitha10 on Apr 17, 2009 5:11 AM Edited by: Smitha10 on Apr 17, 2009 5:54 AM |
That's okay. Everyone makes mistakes. But, you posted your code nicely, with the code tags. You also described the problem well, including the exact error message (not a paraphrase of the error [although your error message code and use case code didn't quite match--one had "null", and one had "null, 7"--the full error message with the carat in the right place ... |
Hi, Please do you know: Is it possible to proscribe that a class must expose a constructor with a particular signature? In the same way the an interface defines the public methods? I know I could use a factory to obviate public constructors, it just seems like a lot of work... more than the problem is worth. Thanks in advance for ... |
A constructor with no parameters will automatically call super(). If I extend an object with a parametered constructor, I need to manually enter that constructor into my subclass constructor "super(a, b)". What then of non extended objects? In this non-extended object if I make a constructor that takes parameters doesn't it automatically make calls to super(). It has to to construct ... |
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Hi all, Our project is having an issue here and we're not sure how to go about rectifying this error...any help or suggestions will be greatly appreciated!!! ***we encounter an error in this line "public CommPortOpen(Frame F)" which we are supposedly to return F variables but it doesn't, instead the program can't be executed and run properly....question is do we need ... |
So would this actually remove the item from my array? And say i initialise an array to size 5. If i dont fill it i would get a null pointer exception. Would this method create that exception by leaving out one item in the array, or would the method reduce the array size to 4? |