Drawing Polygon On Screen - Collections As Arguments
Aug 29, 2014
I have a method that draws a polygon on the screen:
public void poly(List<Point> points) {
//code
}
For the usage of the method, it makes no difference whether points is an array or a List. In fact, switching doesn't even change any of the code in the method since I use a for-each loop. So, my question is, is it a better practice to use a List as an argument, or an array when the method itself doesn't care about which to use?
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Feb 7, 2014
I am trying to draw an image unto the screen, however, nothing appears...
Java Code:
private ImageIcon i = new ImageIcon("image.png");
private Image image;
...
image = i.getImage();
...
g.drawImage(image, (int)(x - r), (int)(y - r), null); mh_sh_highlight_all('java');
Am I doing it right? The program gives me no error, it's just that when I try to draw it, I see nothing.
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Jan 7, 2014
I run this code and a window will pop up, but no graphics :(
I tried to draw a rectangle onto the screen, but it will not show up. I was told to extend JComponent, and I did, but it still does not work.
Java Code:
import javax.swing.*;
import java.awt.Graphics;
import javax.swing.SwingUtilities;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.BorderFactory;
import java.awt.Color;
[Code] .....
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Jun 9, 2014
A method is declared to take three arguments. A program calls this method and passes only two arguments.Will it take the third argument as
1 null
2 void
3 zero
4 Compilation error
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Mar 16, 2015
I'm making a game of checkers for my A2 Computing coursework which is due in within a week. I have completely finished the game, and only thing I have left to do is connect the two JPanels together via a CardLayout that I have made. However I am unsure how to do so
Here is the code from my CardLayout:
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JButton;
[Code] ....
I have kept the code I am displaying to a minimal, hence I have removed all the action listeners for my buttons, anyway the problem I have is that, I would like it so that when the user clicks on the 'Multiplayer' button which is the array button ourButtons[1], it will then transition into my main game screen so that the user can then play a game of checkers.
Here is the main important GUI from my CheckerBoard class:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class CheckerBoard extends JPanel implements ActionListener, MouseListener {
// Main routine that opens an Applet that shows a CheckerBoard
public static void main(String[] args) {
new CLayout();
[Code] ....
Once again kept to a minimal.
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May 8, 2013
I'm working on is to create a program to display an n-sided regular polygon and uses two buttons named +1 and -1 to increase or decrease the size of the polygon. Also enable the the user to increase or decrease the size by clicking the right or left mouse button and by pressing the UP and DOWN arrow keys. So, first off I'm just trying to figure out how to display an n-sided polygon. I have some of the other components started, but I'm just trying to focus on getting this to work.
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Graphics;
import java.awt.Polygon;
[code]....
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Dec 22, 2014
I have a java program which rotates a rectangular polygon. My program is having a problem. As soon as it starts rotating, it shrinks. The polygon is rotating perfectly though. I am trying but unable to figure out the cause.Main class which has an infinite loop (game loop) to rotate polygon continuously :-Java Code:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
[code]....
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Mar 8, 2015
I'm currently trying to do a diamond using Polygon. I have done this so far. It is not drawing a diamond.
import java.applet.Applet;
import java.awt.Graphics;
public class Diamond extends Applet {
int[] a = {-30, 100 , 30, 100};
int[] b = {100, 40, 100, -40};
public void init()
{
}
public void paint(Graphics g)
{
g.drawPolygon(a, b, 4);
}
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Mar 2, 2015
I have a shape, Polygon (javafx.scene.shape.Polygon) and want to test whether a point (javafx.geometry.point2D) is contained within the shape. (contains doesn't work)
I can change the polygon to any type, but I need to be able to create it using the 4 corners points and add it as a child to the Pane.
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Jan 19, 2015
I am making a tile based top-down 2D RPG and am using Box2D for the physics. Since my game is tile-based, there are many tiles on each map that cannot be moved through. This results in many small individual Box2D bodies. This is obviously very inefficient and makes the game lag. Therefore I figured that combining the individual tiles' bodies into larger complex groups would be better.
The way I thought of doing it is to, first, group together tiles into groups of tiles that all share 2 vertices with at least one other tile in the group. Then, for each group I do the following. First I get all of the uncommon vertices (these should be the ones on the outside of the polygon). Then I connect all of those vertices and then remove all of the overlapping lines. This should result in only lines on the outside of the polygon. Then I sort the lines so that the first line in the sorted array shares its end point with the second line's start point, etc. Then I remove the doubled vertices and using those remaining vertices (I called them the "true vertices") I create the polygon. I know that Box2D only supports convex polygons, but with Box2DSeparator I should be able to do this, but I first want this method to actually work.
/**
* Attempts to combine the given blocks into larger bodies to improve performance.
* @param bs The created wall blocks.
* @param w The world. Used for body creation.
*/
private void makeLargeBodies(Block[][] bs, World w) {
Array<Tile> tiles = new Array<Tile>();
for(int i = 0; i < bs.length; i++) {
[Code] .....
However, this is where the first problem arises. This method is extremely slow for large maps (like 200x200 tiles). I have worked at this for very long and right now my head can't figure out how to make the loop more efficient...
Now for the next part. After that I attempt to create the bodies for the TileGroups:
//create all the groups' bodies
size = groups.size;
System.out.println(size + " groups");
for(int i = 0; i < size; i++) {
TileGroup g = groups.get(i);
System.out.println("Starting group " + i + ".");
long timeCheck = TimeUtils.millis();
g.createBody(w);
System.out.println("Group 0 took " + (TimeUtils.millis() - timeCheck) + " millis");
}
*Note that the printing is for debugging purposes*...
This method is probably not a problem; it is what is inside createBody(World) that is the issue...
public void createBody(World w) {
Array<Vector2> allVertices = new Array<Vector2>();
Array<Vector2> uncommonVertices = new Array<Vector2>();
System.out.print("Starting search for uncommon vertices. ");
long timeCheck = TimeUtils.millis();
[Code] .....
Most of the code is self-explanatory (with comments). My current issue is where I connect the uncommon vertices (see the printed statements). This method does not actually finish (I have let it run for several minutes and it does not complete). This is likely due to a large number of vertices (often around 3000 in a 60x60 map), but I cannot figure out how to make the loop more efficient... Because of this early failure I don't know if the rest of the method works, both physically and in theory.
All relevant classes (Tile, TileGroup, Line) are below:
private class Tile {
private Vector2[] vertices;
private TileGroup group;
public Tile(int x, int y) {
vertices = new Vector2[4];
[Code] ....
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Sep 5, 2014
My code is giving me an error at the main method and it says that modifier 'static' is not allowed in constant variable declarations. every program that i searched for had the same code line but none had the problem i do.
package regularpolygon;
/**
*
* @author home1
*/
import java.lang.Math;
import java.text.*;
[code]...
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Jul 2, 2014
I am new in Collection, as per my knowledge I have already override the hashCode() and Equals() method in Data class, but when I trying to search the element it is giving "not found". find the bug.
import java.util.*;
public class WordCounter {
public static void main(String args[])
{
HashSet<Data> set=new HashSet<Data>();
set.add(new Data("this",2));
[code]....
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Apr 23, 2014
I am just not sure of some theory in collections, ArrayList and LinkedList maximum capacity depends on the memory allocated to the JVM. But according to few people those list has a maximum capacity of Integer.MAX_VALUE.
According to my experiment, those list has a maximum capacity of Integer.MAX_VALUE since the get method of List accept a parameter of int primitive type (index of element), therefore we can conclude that the maximum capacity of List is equal to Integer.MAX_VALUE.
But what about the Map? get() method of map accepts object(the key of the map). So does it mean that the maximum capacity of Map depends on the memory allocated to our JVM? Or its maximum size is Integer.MAX_VALUE also just like Lists and Arrays? Is there a way to prove it? Is Map designed to hold infinite number of data (disregarding the heap memory space exception)?
And also about Stack, Deque? is it also the same as Map (in terms of maximum capacity)?
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Aug 24, 2014
Today I installed jdk1.8.0_20 on my computer and typed a simple example code in MyEclipse 6.0 IDE, the code listed below:
import java.util.List;
public class Test5
{
public static void main(String[] args)
{
List<String> features = Arrays.asList("Lambdas", "Default Method", "Stream API", "Date and Time API");
features.forEach(n -> System.out.println(n));
}
}
the MyEclipse Editor shows some errors like "Arrays can not be resolved" and "n can not be resolved".
I did use jdk 8 in the build path, but it seems like the jdk 8 did not function properly.
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Feb 24, 2014
The Iteratior provides the functionality of traversing and removal which we can achieve through normal for loop and remove() of the data structure.Then, why do we need Iterator explicitly and as an inner class?
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Jan 22, 2014
I am using this image as a reference to learn the Collection interface better and it seems I must be getting confused with the 'ordered/unordered' types. I thought ordered would mean ordering the objects automatically like a TreeSet using the comparable interface so it could be numerically or alphabetically ordered etc..
Java Code:
public static void main(String[] args) {
Set hashSet = new HashSet();
hashSet.add(1);
hashSet.add(3);
hashSet.add(2);
for (Object o : hashSet){
System.out.print(o + " "); // Prints: 1,2,3 (Unordered but puts the numbers in order....)
[code]...
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Oct 30, 2014
When I run my code, I get an error with this line
if(Collections.binsearch(dict, word3) != -1) {
I imported the collections utility and everything. Tell me if you need to see more of the code. The exact error is binsearch is undefined for the type Collections.
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Apr 6, 2014
I have searched on internet but did not find something useful. I do not want to use collections. here's what i have written
class ArrayDemo3
{
static void union(int x[], int y[])
{
System.out.println("Union Elements:");
for(int i=0; i<x.length; i++)
{
for(int j=0; j<y.length; j++)
[code]....
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Jul 14, 2014
I am confused with the following function signature in the class java.util.Collections.
static <T> boolean replaceAll(List<T> l, T oldValue, T newValue);
I got the other parts but i could not figure out at all what is the meaning of <T> in the beginning.
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Jun 28, 2014
I am trying to create a java program to sort an array in ascending and descending order. Here is the program I created :
import java.util.Arrays;
import java.util.Collections;
public class ArraySort
{
public static void main(String [] args) {
int [] num = {5,9,1,65,7,8,9};
Arrays.sort(num);
[Code]...
BUT I GET THE FOLLOWING EROOR ON COMPILATION
ArraySort.java:12: error: no suitable method found for reverseOrder(int[])
Arrays.sort(num,Collections.reverseOrder(num));
^
method Collections.<T#1>reverseOrder(Comparator<T#1>) is not applicable
[Code] .....
What's wrong with my program?
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May 11, 2012
I'm doubted regarding the implementation of Collections.binarySearch() method on an ArrayList of objects of a custom class Movie.
Here is the movie class :
public class Movie implements Comparable<Movie> {
String movieName;
String rating;
String director;
String theme;
[Code] .....
The sort/binarySearch in searchByMovieName function is done with natural sorting (and Comparable Interface in Movie class). I mean no comparators involved here. And the comparator that I used for sorting/binarySearching on Movies Director attribute in searchByMovieDirector function is :
public class MovieDirectorComparator implements Comparator<Movie> {
public int compare(Movie movie1, Movie movie2) {
return movie1.getDirector().compareToIgnoreCase(movie2.getDirector());
}
}
But I was not able to implement binarySearch ?? How to implement the binarySearch here. I have google to see only binarySearch working on Arrays or probably ArrayList of String only, but not on ArrayList of custom objects.
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Jan 10, 2014
My friends and me are trying to make online Test taking system. We got a very basic doubt.
We have developed classes and relationship between classes for example : Online Test Taking system will have admin and student class. And Admin will have list of students.. etc.
But question troubled me was: if we use database to store all data for example student details then I can perform all sorts of operations writing sql query and store result in some other database then what is the need of "ArrayList<Student> field in Admin".??
Question is: We can put everything in database and manipulate using database(sql) functions to manipulate it.Then what is the need of Arraylist of anything which is just used to store object details for example student details....??
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Dec 27, 2014
I am going through Thinking in Java, 4th Ed and I came across the section that talks about overloading variable arguments. I tried out a piece of code from the book. (Method and class names not exactly the same).
public class Varargs
{
public static void m1(Character... args)
{
System.out.println("Character");
[code]....
In the above code, the compiler throws an 'Ambiguous for the type varargs' error. The error goes away if the first method is changed to:
public static void m1(char c, Character... args)
why there is ambiguity in the first piece of code and not the second.
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Sep 14, 2014
i have to run my program from the command line...My code is:
public static void main( String[] args )
{
// check command-line arguments
if ( args.length == 2 )
{
// get command-line arguments
String databaseUserName = args[ 0 ];
String databasePassword = args[ 1 ];
[code]....
Now everything works in Netbeans but running it from the command line, i get an error message ".java uses unchecked and unsafe operations".I have added a bit more code to the code above
for (int i = 0; i < args.length; i++) {
System.out.println("args[" + i + "]: "
+ args[i]);
}
Just not sure how to run it from the command line,
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Nov 8, 2014
I am new to JAVA. I need to execute a program, based on the OS. If I am on Mac, the program is a .x and if It is on Windows the program is .exe. The program also requires a line of commands attached to it (i.e. relap5.(x) or (exe) -i inputFile -o outputFile -r restartFile -s stripFile
Here is my coding
String in = " -i ", tfIntdta.getText();
String rst = " -r ", tfRstplt.getText();
String out = " -o ", tfOutdta.getText();
String strp = " -s ", tfStpdta.getText();
if tfStpdta.contains(".csv")
String run = in, rst, out, strp;
else
String run = in. rst, out;
// I want to execute either a .x file or .exe file, depending on if I am
// running the app on windows or mac
run relap5.(x) or (exe) (string run goes here)
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Sep 29, 2014
I have been able to create a no arg constructor and pass empty double, int, and strings but i am not able to pass an arraylist.
class Savings {
private double balance;
private ArrayList <String> transaction = new ArrayList();
public Savings (double B)/>
{
balance = b;
}
public Savings()
{
this(0.0,new ArrayList());
}
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