Develop Reference

Using a Method to update a 2D Array by finding a matching value and then updating with a different input variable

Lets say I have a public class called GameBoard that will be a two dimensional array with 4 rows and 5 columns. The spaces in the array are filed with String values from 1 to 20. A card will be drawn that has a name (King of Spades for example) . If the user inputs 15 I will store it in a String variable called userLocation. What would be the most efficient way to create a method that takes the input location and updates the array with the name of the Card? Would a for loop be most efficient?
public GameBoard() {
square = new String[4][5];
square[0][0] = new String("1");
square[0][1] = new String("2");
square[0][2] = new String("3");
square[0][3] = new String("4");
square[0][4] = new String("5");
square[1][0] = new String("6");
square[1][1] = new String("7");
square[1][2] = new String("8");
square[1][3] = new String("9");
square[1][4] = new String("10");
square[2][1] = new String("11");
square[2][2] = new String("12");
square[2][3] = new String("13");
square[3][1] = new String("14");
square[3][2] = new String("15");
square[3][3] = new String("16");
square[2][0] = new String(17);
square[3][0] = new String(18);
square[2][4] = new String(19);
square[3][4] = new String(20);
}
My preferred method as of now would look something like this but it gives me the error code "type mismatch:cannot convert string to boolean" under userLocation = board[i][j]
public String[][] updateBoard(String userLocation, Card card, String[][] board) {
for (int i = 0; i <4; i++)
{
for (int j = 0; j < 5; j++)
{
if(userLocation = board[i][j]) {
board[i][j] = card.name;
}
}
}
return board;
}

So the reason it will not compile is your = does not return a boolean expression. == would, but it's still not what you want, since you want to check if the String contents are the same, not if they're the same object, so use .equals.
But, no, I think you don't want to depend on strings to identify locations. What if you want to replace a card? And why look through everything when you need not?
Rather if i is some number between 1 and 20, identify the corresponding spot in the array by square[(i-1)/5][(i-1)%5]
That should bypass the issue you are having with matching strings.
So for example, your constructor becomes:
public GameBoard() {
square = new String[4][5];
for (int i=1; i<=20;i++){
square[(i-1)/5][(i-1)%5]=""+i;//initialize with 1 to 20 if you like
}
and userLocation is an int.

Is there a more concise way to instantiate 5 of object-A, 3 of object-B, 1 of object-C, 1 of object-D, all inside one method?

I am currently working through Objects module over on Hyperskills.org. One of the coding challenges is to create five Units, three Knights, one General, one Doctor. We are given the class definition for each object and each object has a constructor that sets one String field.
I took the prompt and just instantiated x-number of X-class as asked.
public static void createArmy(){
Unit unit1 = new Unit("U1");
Unit unit2 = new Unit("U2");
Unit unit3 = new Unit("U3");
Unit unit4 = new Unit("U4");
Unit unit5 = new Unit("U5");
Knight knight1 = new Knight("K1");
Knight knight2 = new Knight("K2");
Knight knight3 = new Knight("K3");
General general1 = new General("G1");
Doctor doctor1 = new Doctor("D1");
}
The compiler accepts my answer but it says, "Correct, but can be improved."
Please and thank you: How else can this code be improved?

You can improve it by putting the units and stuff into an array and using for loops. Also adding some parameters would make calling this function easier later on. ex:
public static void createArmy(int units, int knights, int generals, int doctors){
Unit unit = new Unit[units];
Knight knight = new Knights[knights];
General general = new Generals[generals];
Doctor doctor = new Doctors[doctors];
for(int x = 0; x < units;x++){
unit[x] = new Unit("U"+(x+1));
}
for(int x = 0; x < knights;x++){
knight[x] = new Knight("K"+(x+1));
}
for(int x = 0; x < generals;x++){
general[x] = new General("G"+(x+1));
}
for(int x = 0; x < doctors;x++){
doctor[x] = new Doctor("D"+(x+1));
}
}

NullPointerException and couldn't initialize sketch errors in Processing

I wrote a physical simulation about gravitational force between two planets.It worked perfectly fine so I decided to take it to a new level and rewrote it using arrays and five planets(circles).But my code gives strange and never the same error. I get either NullPointerException error or the VM error when intializing the sketch(No description just the "Vm error couldn't initialize skecth" and the "see help and troubleshoot" bullsh*t) The program uses a txt file to read in data(double-checked and it works fine).
My Array names and descriptions are
PVector - Pos stands for Position
PVector - Vel stands for Velocity
PVector - Acc stands for Acceleration
PVector - Dist stands for Distance
PVector - Dir stands for Direction
float - Mass stands for Mass
My code:
public PVector[] Pos = new PVector[5];
public PVector[] Acc = new PVector[5];
public PVector[] Vel = new PVector[5];
public PVector[] Dist = new PVector[5];
public PVector[] Dir = new PVector[5];
public float[] Mass = new float[5];
void setup(){
String Data[] = loadStrings("Data.txt");
size(800,800);
for(int g = 0;g < 5;g++){
Pos[g] = new PVector(float(Data[g+1]),float(Data[g+6]));
Vel[g] = new PVector(float(Data[g+12]),float(Data[g+17]));
Mass[g] = float(Data[g+23]);
}
}
void draw(){
for (int i = 0;i < 5;i++){
for (int f = 0;f < 5;f++){
if(i !=f){
if(Pos[i].x < Pos[f].x){Dir[f].x = 1;Dist[f].x = (Pos[f].x - Pos[i].x);}else{ // I get the error here
if(Pos[i].x > Pos[f].x){Dir[f].x = -1;Dist[f].x = (Pos[i].x - Pos[f].x);}else{
if(Pos[i].x == Pos[f].x){Dir[f].x = 0;Dist[f].x = 0;}}}
if(Pos[i].y < Pos[f].y){Dir[f].y = 1;Dist[f].y = (Pos[f].y - Pos[i].y);}else{
if(Pos[i].y > Pos[f].y){Dir[f].y = -1;Dist[f].y = (Pos[i].y - Pos[f].y);}else{
if(Pos[i].y == Pos[f].y){Dir[f].y = 0;Dist[f].y = 0;}}}
if ((Dist[f].x != 0)){
Acc[i].x+=((6*((Mass[i]*Mass[f])/Dist[f].magSq())/10000000)/Mass[i])*Dir[f].x;// *6/1000000 is MY G constant
}
if ((Dist[f].y != 0)){
Acc[i].y+=((6*((Mass[i]*Mass[f])/Dist[f].magSq())/10000000)/Mass[i])*Dir[f].y;
}
}
}
Vel[i].x = Vel[i].x + Acc[i].x;
Vel[i].y = Vel[i].y + Acc[i].y;
Pos[i].x = Pos[i].x + Vel[i].x;
Pos[i].y = Pos[i].y + Vel[i].y;
ellipse(Pos[i].x,Pos[i].y,10,10);
}
}

You create array of PVectors of size 5 here : public PVector[] Dir = new PVector[5]; . In this moment, it has null five times for indexes 0-4 in it.
Because you do not create new PVectors in this array, when you try to access variable x in here Dir[f].x, you got error, because Dir[f] is null and you cant access variable x of null -> NullPointerException.
In this part you are instantizing some arrays
for(int g = 0;g < 5;g++){
Pos[g] = new PVector(float(Data[g+1]),float(Data[g+6]));
Vel[g] = new PVector(float(Data[g+12]),float(Data[g+17]));
Mass[g] = float(Data[g+23]);
}
You should add instantizing also for Dir, Acc and Dist
Note also, that you are working with objects, not with primitive data types. null is not same as new PVector(0,0)
Also from "design" point of view, using arrays this way is NOT good approach. You should create your own class Planet, where each planet holds information about its properties and in your main class you handle interaction between them.
How to create "empty" or "zero" variables instead of nulls? Just create them :)
for(int g = 0;g < 5;g++){
Pos[g] = new PVector(float(Data[g+1]),float(Data[g+6]));
Vel[g] = new PVector(float(Data[g+12]),float(Data[g+17]));
Mass[g] = float(Data[g+23]);
Dir[g] = new PVector(0,0);
Acc[g] = new PVector(0,0);
Dist[g] = new PVector(0,0);
}
PS : I do not how exactly is this class implemented, using new PVector() or new PVector(0) instead of new PVector(0,0) may also work.

How to get array data with CATIA using com4j API to get point coordinate?

I try to retreive information from catia usig com4j. Some methods require to pass an array in argument to retreive information but the array is never populated. In this example is to get coordinate from a point in catia.
The declaration of the method generated by com4j
public interface Point extends com4j.catia.HybridShape {
...
void getCoordinates(java.lang.Object[] oCoordinates);
...
}
my code to get the coordinate
public static void testGetPointCoordinates() {
String catiafile="E:\\test.CATPart";
Application app =null;
app = COM4J.createInstance(Application.class, "CATIA.Application");
Documents documents = app.documents();
Document oDocument = (Document) documents.open(new Holder<>(catiaFile.getAbsolutePath()));
PartDocument partDocument = oDocument.queryInterface(PartDocument.class);
Part part = partDocument.part();
Factory HSFactory = part.hybridShapeFactory();
HybridShapeFactory HSF = HSFactory.queryInterface(HybridShapeFactory.class);
HybridBodies hbodies = part.hybridBodies();
int n = hbodies.count();
for (int i = 1; i <= n; i++) {
HybridBody hbody = null;
hbody = hbodies.item(i);
int nbitems = hbody.hybridShapes().count();
for (int j = 1; j <= nbitems; j++) {
String name = hbody.hybridShapes().item(j).name();
System.out.println("name=" + name);
//Object tab[]=new Object[3];
if (name.startsWith("Point.12")) {//true point
HybridShape hs = hbody.hybridShapes().item(j);
Reference reference = part.createReferenceFromObject(hs);
HybridShapePointCoord p3 = hs.queryInterface(HybridShapePointCoord.class);
//works
System.out.println("point name = " + p3.name());
System.out.println(p3.y().value());//display 50.0
//doesn't work
Variant tab[] = new Variant[3];
for (int k = 0; k < 3; k++) {
Variant variant = new Variant();
variant.set(k);
tab[k] = variant;
}
p3.getCoordinates(tab);
System.out.println(tab[1].getParseableString()); //display 1 (value not modified)
//doesn't work
tab = new Variant[3];
for (int k = 0; k < 3; k++) {
Variant variant = new Variant(Variant.Type.VT_EMPTY);//tested with VT_R4 VT_R8,...
tab[k] = variant;
}
System.out.println(tab[1].getJavaCode()); //display null (Don't know how to print VT_EMPTY as an Java literal)
//doesn't work with this other solution but ok in VBA
tab = new Variant[3];
//Variant v = new Variant(Type.VT_EMPTY);
tab[0] = new Variant(Variant.Type.VT_EMPTY);
tab[1] = new Variant(Variant.Type.VT_EMPTY);
tab[2] = new Variant(Variant.Type.VT_EMPTY);
HybridShapePointExplicit point = HSF.addNewPointDatum(reference);
point.getCoordinates(tab);
System.out.println(tab[1].doubleValue() + " " + tab[2].toString()); //display 0
//doesn't work
//crash JVM
// tab = new Variant[3];
// p3.getCoordinates(tab);
break;
}
}
}
}
the code below works in VBA with CATIA
Dim P1
Dim coordonnees(2)
Dim coordonnees2(100, 3)
coordonnees(0) = 0
coordonnees(1) = 0
coordonnees(2) = 0
Set P1 = HSF.AddNewPointDatum(hbody.HybridShapes.Item(i))
'fonction to get coordinates
P1.GetCoordinates coordonnees
'set name and coordinates
coordonnees2(Y, 0) = hbody.HybridShapes.Item(i).name
coordonnees2(Y, 1) = Round(coordonnees(0), 3)
coordonnees2(Y, 2) = Round(coordonnees(1), 3)
coordonnees2(Y, 3) = Round(coordonnees(2), 3)

I'm not familiar with com4j, but Point.GetCoordinates is a restricted method:
.
The solution to this problem in VB is you need to create a new variant and set it equal to p3. Then, call GetCoordinates from the variant's context. Intellisense will not work well on the variant, but the call to GetCoordinates will work.
In VB the code would look something like this:
...
Dim p3 As Variant
Dim arrayOfCoord(2) As Variant
Set p3 = hybridShapePointCoord1 'set variant = strongly typed point object
p3.GetCoordinates arrayOfCoord
...
In your case, non-VB, your code might look like this
...
Object p3Obj; //used in vb:Variant p3Var;
p3Obj = p3;
p3Obj.GetCoordinates(tab);//Intellisense will not work, but the call to this method should
...
Let me know if this works.

Access already running objects - Java

import java.awt.*;
import javax.swing.*;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableColumn;
public class vasilisTable extends JFrame {
Object[] split_data_l;
Object[][] split_data;
Object [][] split_data_clone;
Object [][] split_data_reverse;
Object [][] split_data_reverse_num;
String[] temp;
private JTable table;
private JPanel bottom_panel;
private JLabel average;
private JLabel max_dr;
public vasilisTable(String name, String data, int choice)
{
super(name);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); //the DISPOSE_ON_CLOSE means that when we press the x button is will close only the table window and not the whole programm
//this.getAccessibleContext().setAccessibleName(name);
//System.out.println(this.getAccessibleContext().getAccessibleName());
setSize(800,600);
String[] columnNames = {"Date", "Open","High","Low","Close",
"Volume", "Adjusted" };//defines the column names
//------ Start of making the arrays that will be used as data for the table creation
split_data_l = data.split( "\n" );
int lngth = split_data_l.length;
split_data = new Object[lngth-1][7];
split_data_clone = new Object[lngth-1][7];
split_data_reverse= new Object[lngth-1][7];
split_data_reverse_num= new Object[lngth-1][7];
double sum = 0;
for(int k=1; k<split_data_l.length; k++) //initializing the three arrays with the data we got from the URLReader
{
temp = split_data_l[k].toString().split(",");
for (int l=0; l<temp.length; l++)
{
split_data[k-1][l] = temp[l];
split_data_clone[k-1][l] = temp[l];
split_data_reverse[k-1][l] = temp[l];
split_data_reverse_num[k-1][l] = temp[l];
}
}
for(int k=split_data_l.length-2; k>=1; k--) // making of the clone array that contains all the last column with colours
{
Double temp = Double.parseDouble(split_data[k][6].toString());
Double temp1 = Double.parseDouble(split_data[k-1][6].toString());
double check =temp-temp1;
if (check>0)
{
String color_temp = "<html><span style = 'color:red'>" + split_data_clone[k-1][6] +"</span></html>" ;
split_data_clone[k-1][6] = color_temp;
}
else
{
String color_temp = "<html><span style = 'color:green'>" +split_data_clone[k-1][6]+"</span></html>" ;
split_data_clone[k-1][6] = color_temp;
}
}
int l = split_data_clone.length;
int m = l-1;
for (int i=0; i<l; i++) //making of the reversed array
{
for (int j = 0; j<=6; j++)
{
split_data_reverse[i][j]=split_data_clone[m][j];
}
m--;
}
m = l-1;
for (int i=0; i<l; i++) //making of the reversed array
{
for (int j = 0; j<=6; j++)
{
split_data_reverse_num[i][j]=split_data[m][j];
}
m--;
}
//------ End of making the arrays that will be used as data for the table creation
//------ Start of calculating the average
for (int i=0; i<lngth-1; i++)
{
Double temp = Double.parseDouble(split_data[i][6].toString());
sum = sum+temp;
//System.out.println("turn "+i+" = "+split_data[i][6]);
}
float avg = (float) (sum/(lngth-1));
avg = Round((float) avg,2);
String avg_str;
avg_str = "<html>Average: <b>"+avg+"</b></html>";
//"<html><b>Average: </b></html>"
//------ End of calculating the average
//------ Start of Calculating the Maximal Drawdown
double high=0;
double low=100000000;
double drawdown=0;
double max_drawdown=0;
int last_high=0;
int last_low=0;
for (int i=0; i<lngth-1; i++)
{
Double temp = Double.parseDouble(split_data_reverse_num[i][6].toString());
//Double temp1 = Double.parseDouble(split_data[i+1][6].toString());
if (temp>high)
{
high = temp;
last_high = i;
//System.out.println("max high = "+temp);
}
else
{
low = temp;
last_low = i;
//System.out.println("max low = "+temp);
}
if (last_low>last_high)
{
drawdown = high-low;
//System.out.println("drawdown = "+drawdown);
}
if (drawdown>max_drawdown)
{
max_drawdown = drawdown;
}
}
//System.out.println("max dr = "+max_drawdown);
String max_dr_str = "<html>Maximal Drawdown: <b>"+max_drawdown+"</b></html>";
//------ End of Calculating the Maximal Drawdown
average = new JLabel(avg_str);
max_dr = new JLabel(max_dr_str);
bottom_panel = new JPanel();
String space = " ";
JLabel space_lbl = new JLabel(space);
bottom_panel.add(average);
bottom_panel.add(space_lbl);
bottom_panel.add(max_dr);
//-------- Start of table creation ---------
if(choice==1)
{
table = new JTable(split_data_clone, columnNames);//creates an instance of the table with chronological order
}else
{
table = new JTable(split_data_reverse, columnNames);//creates an instance of the table with reverse chronological order
}
TableColumn column = null;
for (int i = 0; i < 7; i++) {
column = table.getColumnModel().getColumn(i);
if (i == 0) {
column.setPreferredWidth(100); //third column is bigger
} else if (i == 5) {
column.setPreferredWidth(85); //third column is bigger
}
else if (i == 6) {
column.setPreferredWidth(70); //third column is bigger
}
else {
column.setPreferredWidth(50);
}
}
table.setShowGrid(true);
table.setGridColor(Color.black);
//-------- End of table creation ---------
JPanel table_panel = new JPanel (new BorderLayout());
JScrollPane table_container = new JScrollPane(table); // create a container where we will put the table
//table.setFillsViewportHeight(true); // if the information are not enough it still fill the rest of the screen with cells
table_panel.add(table_container, BorderLayout.CENTER);
table_panel.add(bottom_panel, BorderLayout.SOUTH);
//table_panel.add();
setContentPane (table_panel);
pack(); // here i pack the final result to decrease its dimensions
}
public float Round(float Rval, int Rpl) // this functions rounds the number to 2 decimal points
{
float p = (float)Math.pow(10,Rpl);
Rval = Rval * p;
float tmp = Math.round(Rval);
return (float)tmp/p;
}
}
I am making an application which creates various instances of a class. These instances are actually some windows. After having create multiple of these windows, how can I access one of them and bring it in front? I know the .tofront() method, but how can I specify the window that I want to bring in front?
Above is the code that creates every window. My main problem is that after I have create e.g 5 windows, how can I access one of them?
ps
code that creates each window:
if (sData != null) {
//System.out.println("Success, waiting response");
vasilisTable ftable = new vasilisTable(name, sData, choice);
hashMap.put(name, ftable);
ftable.setVisible(true);
//choice=2;
}

My main problem is that after I have create e.g 5 windows, how can I access one of them?
You have to keep a reference to the relevant objects in variables or an array or a collection or something. The "bring it to the front" function needs to:
figure out what domain object needs to be brought to the front,
lookup its corresponding JFrame, and
call toFront() on it.
Java provides no built-in mechanisms for finding previously created instances of objects.

When you create your various instances of the above JFrame, you can keep track of the created instances, may be store them within a HashMap, then you can pick the right JFrame instance basing on its designated name and bring it to the front. Have a look at the below code for more illustration:
HashMap<String, VasilisTable> hashMap = new HashMap<String, VasilisTable>();
JFrame firstWindow = new VasilisTable("firstWindow",data, choice);
hashMap.put("firstWindow", firstWindow);
JFrame secondWindow = new VasilisTable("secondWindow",data, choice);
hashMap.put("secondWindow", secondWindow);
JFrame thirdWindow = new VasilisTable("thirdWindow",data, choice);
hashMap.put("thirdWindow", thirdWindow);
// To bring a certain window to the front
JFrame window = hashMap.get("firstWindow");
window.setVisible(true);
window.toFront();

Are these JFrame or JWindow objects? If they are you can call -
jframe.setVisible(true);
jframe.toFront();
This is something interesting I found at the API doc.
Places this Window at the top of the stacking order and shows it in
front of any other Windows in this VM. No action will take place if
this Window is not visible. Some platforms do not allow Windows which
own other Windows to appear on top of those owned Windows. Some
platforms may not permit this VM to place its Windows above windows of
native applications, or Windows of other VMs. This permission may
depend on whether a Window in this VM is already focused. Every
attempt will be made to move this Window as high as possible in the
stacking order; however, developers should not assume that this method
will move this Window above all other windows in every situation.
I would recommend you to check out these answers as well.
Java Swing: JWindow appears behind all other process windows, and will not disappear
Java: How can I bring a JFrame to the front?