But for the method get() of Paths, I get this error in eclipse.The method get(String, String[]) in the type Paths is not applicable for the argument..Yet on the Oracle documentation site, it uses a similar example:
I am trying to pass an object of type Product p to my editProduct method, however trying to call p.getName(); doesn't work and throws a NullPointerException. The same kind of thing works for my displayRecord method (in a different class) and I can call .getName() on Product p, also passed as an argument to that method. Below is my editProduct class. The NullPointerExcepion is being thrown at line 61 (i.e., nameField.setText(p.getName());).
I don't know if I explained right, so here's a line thing of how the classes relate:
And as a side note: adding the line p = new Product(); fixes it and successfully runs the class (including the Save and Quit parts) but obviously I want it to specifically refer to the Product I pass to the method.
I'm asking a question because I don't understand how Product p could possibly be null, because the argument is passed through my DisplayRecord class, which also takes a Product p argument and works. In that class, I have declared Product prod = p; and prod is what I am passing to editProduct.
I am having a bit of difficulty understanding/Using FileWriter. Now by my understanding in the API FileWriter allows to use write at the end of your file, if you have text in there already, correct?
I have a file with people info in it. And I created a GUI which allows people to input that data.
Java Code:
File file = new File("People.txt"); FileWriter fw = new FileWriter(file); People p = new People(firstName, lastName, email, sex)); fw.append(p); fw.close() mh_sh_highlight_all('java');
Now, I keep getting an error on the fw.append(p)
Java Code:
The method append(CharSequence) in the type Writer is not applicable for the arguments(People) mh_sh_highlight_all('java');
I have learn that every function in java is treated as a normal function including main() except that execution of a program starts here. I tried to overload it.
But I am getting error while doing so via String type array as an argument of main.
class Hello { public static void main() { System.out.println("Hello"); } public static void main(String... s) { System.out.println("main from Hello");
One interviewer has asked me one question that why main() method has argument "String[] arg".What is reason behind this ??I am unable to explain it because i never think about it ..
I need to write a method that will consume string representation of Object type and will return one object of this type. How to set return type for the method in this case?
Here is exmaple :
public <?> identifyType(String typeString){ if (typesString.matches("String")){ return new String(""); }else if (typeString.matches("Integer")){ return new Integer(0); } //....etc..}
The two last methods stumped me. The return type to each is "DateTime", according to JUnit complaints.I know that I can use the "this" keyword to reference to the object. But how do I get these two methods to return the correct result?
public static void doSomething(List<? extends GenericClass> input) { // op }
^
This compiles and works, ensuring I can only pass in a List of a type extending GenericClass.But now I want it to accept an Array instead of List. This is where I'm stuck:
public static void doSomething(<? extends GenericClass>[] input) { // op }
^
A wrong guess at the syntax which does not compile. One solution is to convert Array into ArrayList before calling the 1st method above, but I'd rather bypass this if possible.
So I want to know how in Java you can pass a unkown type into a method (type can be an int, double, or a user defined object) and return that unkown type.
example of what I want: Java Code: public (unknowntype)[] method2 ((unknowntype)[]) //Process Data //unknowntype.process(); return (unknowntype); } mh_sh_highlight_all('java');
I know in C you can use void pointers and in c++ we have templates but I do not know how java handles this. Also I want to know if it is possible to call a method in the unknowntype.
Is there a reason why this error is occurring? I can't identify what's causing it to happen.
Java Code:
package tictac1; import java.util.*; public class TicTacToe{ //Instance variables private char[][] board; //2D array of chars for the board public TicTacToe(){ //creates a board where each space holds whitespace board = new char[3][3]; for (int row = 0; row < 3; row ++){
I am following this article [URL] .... till now I have made some code
This is my Interface
public interface Comparable<T> { public int compareTo(T o); }
And this is my class where I am using Bound Type Parameter on Generic Methods
public class GenericMethodBoundType { public static <T extends Comparable<T>> int countGreaterThan(T[] anArray, T elem) { int count = 0; for (T e : anArray)
[Code] .....
What else I need to do both in main method and at what parameterized types I need to pass at the class?
public void randomCreate(ParentObject obj){ int x = random(0-4); //pseudo int y = random(0-4); //pseudo create new ParentObj(x,y); }
ParentObject is actually abstract, so you would only ever pass one of its children objects to it, and a child object of that type would be created. It seems like there should be a way to pass a type, rather than an object, and then create an instance later down, but I don't know if that is actually possible, or if it is poor programming style.
I'm trying to make a puzzle that gets the user input and moves the rows either to the left or right, the columns move either up or down depending on what the user wants. The problem I'm getting is a type mismatch for my RL method which moves the rows to the left.
import java.util.*; import java.io.*; public class Numbrosia { static int [][] board = new int [5][5]; public static void main(String[]args){ Scanner scan = null; try{
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 trying to make a ChessBoard class composed of an array of JLabels inside a JPanel with a grid layout. I am also trying to override the getPreferredSize method so that the board will change size when I resize the main window (in another class in which I will instancize this class as part of a larger GUI). I got this kind of layout working before, but now I am trying to get it to work with multiple classes. However, after copying in the part of the previous code corresponding to the panel's layout, I am encountering some errors that I don't know how to solve. Specifically, when I try to override the getPreferredSize method, the compiler tells me "method does not override or implement a method from a super type, " and that it can't find the method "getPreferredSize"
Here's my code:
public class ChessBoard extends JPanel//the panel that this class extends is the boardHousing { //mental chess board piece array Piece mentalBoard[][] = new Piece[8][8]; //actual GUI chessboard JLabel Array static JLabel chessBoard[][] = new JLabel[8][8];
[Code] ....
I would just think that I was overriding the method incorrectly, but the weird thing is that I got that specific section of code to work before -- the only thing different now is that there are multiple classes, so my ChessBoard class itself is extending JPanel.
I am trying to implement the following example to override the equality and hashCode method if the class has reference type member. I do get the expected result "true" for equal and "false" for non-equal objects. But the print statement in the Circle's equal method is not executed when the objects values are not equal. I don't know what i am missing, though i get the equality result "false" as expected for non equal objects.
class Point{ private int x, y; Point (int x, int y) { this.x =x; this.y = y;
I've just been having a go at an exercise where I have to create and use a class called Point, with two fields of type double. I have to create some methods for it, one of which is a distanceTo(Point) method, that calculates the distance to another point. I've tried to keep the distanceTo(Point) method short so have created some other methods to use within the method. My question is about the getDistance() method that I've made. As you can see below, I've given it two parameters, which are references to values within two Point objects (this.x and otherPoint.x).
I know what the tree data structure is, how it works, etc., but I need to design a method that will sequentially print out all the paths in the tree (i.e. for each node).
The pseudocode I was thinking of doing was something along the lines of:
paths if(root.getData() = null) return paths; path = ?; // absolutely no clue what to do here paths += root.getData() + " " + path + " "; if(root.hasLeftChild()) { newPath += "0"; paths += begin recursion; } if(root.hasRightChild()) { newPath += "1"; paths += begin recursion; } return paths;
Problems:
(1) I don't know how to determine "path" before the left and right children check (the root node's path is "", the first left node's path is "0", the first right node's path is "1", pattern continues with left being "0" and right being "1"). (2) I don't know where to put newlines precisely. (3) I'm not sure how to get the print layout precisely as it is supposed to be. At most I've been able to just get the last number in the sequence (i.e. if it was supposed to be "1000", I could get "0".
I am working with the pseudocode formulation, especially in regards to the logic and formatting. I think once I have an understanding of what is going on, I can solve it. And yes, I've gone through a couple pseudocode rewrites (a few hours worth) and haven't gotten anywhere which is slightly unnerving.
I can't get Relative paths to work. I have created the class.dat file and I can't get java to recognize it. I am using Eclipse as an IDE. Was wondering if I could get Eclipse to recognize it. I tried with a .txt file as well and couldn't get that to work.
import java.io.*; public class ReadBytes { public static void main(String[] args) { try { FileInputStream file = new FileInputStream("class.dat");
