how to 'implement' an interface and 'extend' a class. Now I want to try and recall the information by memory without using any reference material.
Implementing an interface...
Java Code: //This interface will hold information for cell phones//Like saying... you can't BE a cell phone unless you have this information, at the very least
public interface CellInfo {
public void model();
public void make();
public void androidVer();
}
//Now I implement the interface for a class called Galaxy, which is a class about a specific phone
public class Galaxy implements CellInfo
public void model() {
System.out.println("I'm a Galaxy S5.");
}
public void make() {
System.out.println("I'm made by Samsung.");
In the following program i have called the anonymous class of dev class.
interface emp { void desig(); } public class dev implements emp { dev e = new dev() //this line is throwing error ...works fine if i use emp instead of dev {
[Code] .....
i am getting stack over flow error as :
Exception in thread "main" java.lang.StackOverflowError at dev$1.<init>(dev.java:17) at dev.<init>(dev.java:16) at dev$1.<init>(dev.java:17)
[Code] .....
Is it because the jvm is not able to decide which of the 2 desigs() it has to load in the memory when its object is created in the main..??
I am trying to implement this method in another class but I'm not sure how to do so. My attempt is:
public getCalls(){ return getCalls(); }
When I run the program it sends the following exception:
Exception in thread "main" java.lang.StackOverflowError at FibonacciForget.getCalls(FibonacciForget.java:14) and it highlights the [return getCalls();] part.
What is the correct way to implement the getCalls() method?
Below is the requirements and code. I am getting the error CODELAB ANALYSIS: LOGICAL ERROR(S)We think you might want to consider using: >
Hints:
-Correct solutions that use equals almost certainly also uses high -Correct solutions that use equals almost certainly also uses low
Assume the existence of a Widget class that implements the Comparable interface and thus has a compareTo method that accepts an Object parameter and returns an int . Write an efficient static method , getWidgetMatch, that has two parameters . The first parameter is a reference to a Widget object . The second parameter is a potentially very large array of Widget objects that has been sorted in ascending order based on the Widget compareTo method . The getWidgetMatch searches for an element in the array that matches the first parameter on the basis of the equals method and returns true if found and false otherwise.
public static boolean getWidgetMatch(Widget a, Widget[] b){ int bot=0; int top=b.length-1; int x = 0; int y=0; while (bot >= top)
how it is decided which class will implement a session listener interface? Which class will implement HttpSessionListener? Which one will implement HttpSessionActivationListener, HttpSessionBindingListener or HttpSessionAttributeListener?
How do you enforce any class which implements an interface should also implement comparable too? Say for instance you may have an interface
public interface Task { ... } public class DoThis implements Task { ... } public class DoThis1 implements Task { ... }
I want all of the classes which implements the interface Task to implement comparable too. Of course I can just say implements Task, Comparable. But is there something which we could do from interface level, i mean interface Task level?
I have been researching the Iterator and making a class implement iterable. I have seen this example shown below and was wondering how I could change this so that iterable() is not called upon in the main. I would like to be able to make a method that returns an instance of a class that implements the Iterator interface hopefully an inner class. This is because my program will not have a main and will be supplied with a main that includes a new Object with will use the iterator method.
import java.util.*; public class IteratorDemo { public static void main(String args[]) { // Create an array list ArrayList al = new ArrayList(); // add elements to the array list al.add("C");
[Code] ....
This is all I have been able to understand from what I want to do. This does not work and this is what I am trying to achieve
public class MyArrayList implements Iterable { public static final int DEFAULT_SIZE = 5; public static final int EXPANSION = 5; private int capacity; private int size; private Object[] items;
I want to extend hashCode method in my class. As we know that hashCode is generating with 32 bit. Now I wanna generate 64-bit hashCode for user given Input.. Input may be string or Integer.
Please let me know.. take me out from this problem..
MY code follows like this...
package hash_table; public class Hash_table { private int num; private String data; public boolean equals(Object obj) { if(this == obj)
I need to implement the attached interface ("Locality"). In the attached UML diagram it has a 1 on 1 relationship with the class "Team". I don't know if this can be somehow implemented in Java. Can I create the attribute "team" in the Locality interface and let it be used by the "Town" and "City" classes? Could it be better to implement it as an abstract class instead?
I am working with a program where I am required to use a JFrame in a child class. The only way that I know how to access a JFrame is to do, example (public class Example extends JFrame), but since it is already extending the parent class, I am kind of stuck. I do not think that you can extend two separate classes, so..... I am stuck.
if i call a class that implements an interface the method inside the interface will be triggered automatically by the compiler or happens only in the observer pattern? i keep simple to be surr the message came across, a typical example would be a listener on a button, or a collection that calls comparator)
if some of you worked with Unity Game engine (C#) the idea is that game has main loop and once per cycle it call for example Update() method in all objects which implement certain interface.
I would like to repeat such pattern in Java for another another program, not even game related, but I would still need a main loop and event driven behaviour with async call backsSo question is how to implement the fallowing scenario:
Imagine i have interface which implement some methods and one of them is Execute()
I have the main controller class which implement main loop, also multiple other classes which implement the same interface with method Execute(). How can i call this Execute() method on all objects which implement that interface each loop cycle?
Should i keep and track reference of each object which was implemented with this interface and go through inner "for" loop trough each reference and call manually Execute() method in each of them?what if each object implementing interface have to run Execute() method simultaneously? in parallel independent from each other?
Referring back to Unity engine and their Update() method - there is exactly the same situation:you can have multiple objects with script attached, thats script implement interface which has multiple methods and one of them is Update() and once per cycle all objects with that Update() method will be executed in parallel independently
I am writing a game in Java for Android (although my question isn't Android or Game Dev specific).
I have a SceneManager class and a Scene interface and then various other classes that implement the Scene interface (Code at the end of this post).
Basically, in my MainGame class (which also implements the Scene Interface for Touch Event capturing purposes) I hold the bulk of my game code. Methods in this class are then called from my Level classes. (most of these are needed in all levels so it makes sense to hold them here and call them from the levels to eliminate unnecessary code duplication)
So, I have Level1, Level2......... Level20 classes which all implement Scene.
Now, the problem comes because in only 2 of my Levels something can happen (that can't in the other 18) and I need to run a response method in these 2 levels (the method isn't exactly the same, the response to this event happening is different for both levels).
To run common methods from my classes, I use my Scene Manager like this:
This works great as all Level's have an updateLogic(); and render(); method.
So from my mainGame class, I am doing something like : (pseudo code)
public void checkIfSomethingHappened(){ if (something happens){ if (currentLevel==5){ Level5.response();}
[Code]....
The above would be called from my 2 level classes. So something like:
MainGame.checkIfSomethingHappened(); //Called in addition to the normal methods that make up that level
I don't really want to have this (second) 'if' statement here in the middle of my performance critical game loop.
What I'm after is something like this:
if (something happens){ SceneManager.getInstance().getCurrentScene().response(); }
However, this would require me to put stubs in the other 18 classes.
I'm thinking there must be a way to do this as the SceneManager already knows the current scene so it seems a waste checking it again via an if (or switch) statement. What is the best way to do this without having to put stubs into classes that don't require this method?
abstract class A class B extends A class C extends B class D extends C implements SomeInterface
I'm trying to implement a method "doSomething" declared in SomeInterface in class D. While trying to call doSomething in main I get the error message ”The method doSomething is undefined for the type B”
This is my code i main:
B container = new D("1,2,3,4,5,6,7,8"); System.out.println(container.doSomething());
I need container to be an object of type B, because it goes later into a list of type B. According to what I've been told, the only file I need to edit to make this work is class D.
I am a beginner here at JAVA and I am trying to program a Gratuity Calculator using both interface class and object class but it keeps on compiling with errors saying "cannot find symbol".I tried everything to fix it but it just keeps on stating symbol.
[CODE] public class GratuityCalculator extends JFrame { /* declarations */
// color objects Color black = new Color(0, 0, 0); Color white = new Color(255, 255, 255); Color light_gray = new Color(192, 192, 192);
I would like to implement a variable in a class that is used in another class, how can I do that?
I have a Mall class and a Customer class I would like to associate the position of the customer that is in the Mall class and also implement the same in the Customer class.
Here is a small part of the code without all the methods.
//the two objects Mall m = new Mall("RandomMall",50,30); Customer c1= new Customer("Jack",1240); //the first part of the mall class without the methods class Mall{ private String name; private int width,length; String[][]grid = new String[width][length];
I'm writing a simple queue program using a netbeans as a GUI program I've used netbeans GUI editor to create the GUI my main problem was I've written the queuing code to a button function it works but it runs only once and the queue becomes empty on the second run. So I implemented a class which will create the queue outside the button click event but when I do that I get a Symbol not found: method error . The place where I get the error:
I am a beginner at Java programming. how to implement my own String class, but I have to provide my own implementation for the following methods:
public MyString1(char[ ] chars) public char charAt(int index) public int length( ) ublic MyString1 substring(int begin, int end) public MyString1 toLowerCase( )
[code]....
I have looked through the API, but I don't really understand where to start.
While learning how to implement the class DynamicArrayStack, I've run into some operators and syntax I'm unfamiliar with!
public class DynamicArrayStack{ protected int capacity public static int MINCAPACITY=1<<15; protected int[] stackRep; protected int top = -1; //initializes stack to use an array of default length public DynamicArrayStack() this(CAPACITY)
I know whats the interfaces and abstract class and also know that difference between interface and abstract class,but here my doubt is eventhough abstract class more advantage than the interface,then why should we use interfaces and when?
class Super { static String ID = "QBANK"; } class Sub extends Super{ static { System.out.print("In Sub"); } } public class Test{ public static void main(String[] args){ System.out.println(Sub.ID); } }
According to me output should be "QBANK" In Sub...BECAUSE sub default constructor will call super() constructor.. below is the definition in jls which i am unable to understand ....
A class or interface type T will be initialized at its first active use, which occurs if:
T is a class and a method actually declared in T (rather than inherited from a superclass) is invoked.
T is a class and a constructor for class T is invoked, or T1 is an array with element type T, and an array of type T1 is created.
A non-constant field declared in T (rather than inherited from a superclass or superinterface) is used or assigned. A constant field is one that is (explicitly or implicitly) both final and static, and that is initialized with the value of a compile-time constant expression . Java specifies that a reference to a constant field must be resolved at compile time to a copy of the compile-time constant value, so uses of such a field are never active uses.
All other uses of a type are passive. A reference to a field is an active use of only the class or interface that actually declares it, even though it might be referred to through the name of a subclass, a subinterface, or a class that implements an interface.
I am new to java coding.... When we create anonymous inner class for interface, we get one object for the sublcass of that interface .
In interface there is no constructor then how do we get that object. We know that to create Anonymous inner class we should use one super class constructor.
This assignment uses the following description to implement a Dialog class for the Leap Year Problem. We need to decompose this problem into 2 classes:
1.The Date.java class: is a public class that represents a date composed of a month , day, and a year. So you need to declare month, day, and year as integers. Date has 1 constructor and 4 methods. Write the constructor for Date which has 3 parameters: int m, int d, int y ; (As an example of a constructor with 2 parameters for example chapter 3 page 152 code listing 3-13 has a perfect example for you to use which is the BankAccount.java.) and the 4 methods:
"dayIs()" which returns a day. It has no parameter. "monthIs()" which returns a month. It has no parameter. "yearIs()" which returns a year. It has not parameter. "isLeapYear()" which returns a boolean value.
"isLeapYear()" has one parameter year and returns a boolean. Write the method isLeapYear() knowing that a year is defined to be a leapyear it is a multiple of 4, and if it is is a multiple of 100, it must also be a multiple of 400. isLeapYear() thus decides when a year is a leap year. (see the discussion on "Hints for Assign5" to discover specific examples of a LeapYear).
The purpose of the Date.java is to decide whether a year is a leap year. Here is a definition of when a year is considered a leap year :
-year y1 is a leap year if it is multiple of 4. -year y1 is a leap year if it is a multiple of 100, it must be a multiple of 400. -Otherwise y1 is not a leap year.
2. The DateJDialog.java class: implements the GUI. Please use the Dialog boxes developed in the book in chapter2 in pages 99-100 in the code-listing 2-32 (NamesDialog.java) for input and output.
Remember that you will prompt the user to enter: -a month; -a day; -a year
And out of these 3 you will be able to create a Date. Then you will use the dialog box to tell the user whether the year entered was a leapyear or not a leapyear.
Remember that we defined in 1- what it means a year is a leap year or not a leap year.
Do not forget to compile the 2 java files. To verify that the DateJDialog.java works, in TextPad after you compile DateJDialog.java, Click on Tools, Click on "Run Java Application".
When you have completed the assignment, please remember to submit Date.java and DateJDialog.java.
I am working on a problem that computes primes. Here is the problem: You are going to implement a class that computes all the primes up to some integer n. The technique you are to use was developed by a Greek named Eratosthenes who lived in the third century BC. The technique is known as the Sieve of Eratosthenes. The algorithm is described by the following pseudocode:
create a queue and fill it with the consecutive integers 2 through n inclusive. create an empty queue to store primes. do { obtain the next prime p by removing the first value in the queue of numbers. put p into the queue of primes. go through the queue of numbers, eliminating numbers divisible by p. } while (p < sqrt(n)) all remaining values in numbers queue are prime, so transfer them to primes queue
You are to use the Queue interface provided. When you want to construct a Queue object, you should make it of type LinkedQueue. These classes are included. You should define a class called Sieve with the following public methods:
Sieve() - Constructs a sieve object.
void computeTo(int n) - This is the method that should implement the sieve algorithm. All prime computations must be implemented using this algorithm. The method should compute all primes up to and including n. It should throw an IllegalArgumentException if n is less than 2.
void reportResults() - This method should report the primes to System.out. It should throw an IllegalStateException if no legal call has been made yet on the computeTo method. It is okay for it to have an extra space at the end of each line.
int getMax() - This is a convenience method that will let the client find out the value of n that was used the last time computeTo was called. It should throw an IllegalStateException if no legal call has been made yet on the computeTo method.
int getCount() - This method should return the number of primes that were found on the last call on computeTo. It should throw an IllegalStateException if no legal call has been made yet on the computeTo method.
Your reportResults method should print the maximum n used and should then show a list of the primes, 12 per line with a space after each prime. Notice that there is no guarantee that the number of primes will be a multiple of 12. The calls on reportResults must exactly reproduce the format of the sample log. The final line of output that appears in the log reporting the percentage of primes is generated by the main program, not by the call on reportResults.
Here is my class Sieve. I am having difficulty getting all the primes into the proper queue:
public class Sieve { private Queue<Integer> primes; private Queue<Integer> numList; private boolean computed = false; private int max; private int count = 0;
[Code] ....
When I input say, 20, I only get 2, 3, and 11 back as primes. Somewhere in the algorithm (lines 40-54) I seem to have gone awry, but I'm not certain where. Here are the other classes:
SieveMain: // This program computes all the prime numbers up to a given integer n. It uses the classic "Sieve of Eratosthenes" to do so.
import java.util.*; public class SieveMain { public static void main(String[] args) { System.out.println("This program computes all prime numbers up to a"); System.out.println("maximum using the Sieve of Eratosthenes."); System.out.println();
