How to overwrite an array?

Question

I am trying to overwrite the values in an array, but I am getting an ArrayIndexOutofBoundsException.
This is how I am attempting to do it:
if ((checkTempEnergy(tempDistance, numIons, Q)) < (checkEnergy(distance, numIons, Q))) {
     for (int i=0; i < numIons; i++) {
          arrayX[i] = tempX;
          arrayY[i] = tempY[i];
          arrayZ[i] = tempZ[i];
          distance[i] = tempDistance[i];
The code compiles. Both arrays are the same size and declared the same way. The only difference is the name. Any help would be greatly appreciated, and I will award the 10 DUKE Stars.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

DrLaszloJamf wrote:
You've been posting this question over and over and the drill should be familiar to you by now:
1. Posting a snippet like that isn't really helpful to forum readers. For one thing, the fact that your code has such a trivial error in it makes you an unreliable reporter. Why should we believe what you claim?Ok, but the program is not complete, repeats itself, and looks awful. It is compilable though.
public class FormingSalt2
     //creates a cube for the salt to form
     public static double volCube (double side) {
          double volume = side*side*side;
     return (volume);
     //create a random coordinates within the cube
     public static double randomCoord (double side) {
          double ranCoord = (double) (Math.random() * (side-3.76));
     return (ranCoord);
     //check the distances between ions but without double checking and without checking the distances between the same ions.
     public static double[] checkDistance (double arrayX[], double arrayY[], double arrayZ[], double distance[], int numIons) {
          //check the distances
          int l = 0;
          for (int i=1; i<numIons; i++) {
               for (int j=0; j<i; j++){
                    double dx = arrayX[i] - arrayX[j];
                    double dy = arrayY[i] - arrayY[j];
                    double dz = arrayZ[i] - arrayZ[j];
                    distance[l] = Math.sqrt((dx*dx) + (dy*dy) + (dz*dz));
                    //System.out.println(tempDistance[l]+" is the distance "+ l);
                    l++;
     return distance;
     //check the temporary distances between the randomly moved ions but without double checking and without checking the distances between the same ions.
     public static double[] checkTempDistance (double tempX[], double tempY[], double tempZ[], double tempDistance[], int numIons) {
          //check the distances
          int l = 0;
          for (int i=1; i<numIons; i++) {
               for (int j=0; j<i; j++){
                    double dx = tempX[i] - tempX[j];
                    double dy = tempY[i] - tempY[j];
                    double dz = tempZ[i] - tempZ[j];
                    tempDistance[l] = Math.sqrt((dx*dx) + (dy*dy) + (dz*dz));
                    //System.out.println(tempDistance[l]+" is the distance "+ l);
                    l++;
     return tempDistance;
     //checks the Total Energy between the ions
     public static double checkEnergy (double distance[], int numIons, double Q[]) {
          final double EPSILON = Math.sqrt(35.6*120), SIGMA = ((2.75+3.41)/2), K1 = 2.30, K2 = 0.0000552;
          double E1=0, E1sum=0, E2=0, E2sum=0;
          for (int i=1; i<numIons; i++) {     
               for (int j=0; j<i; j++) {     
                    E1 = (K1) * ((Q[j]*Q)/distance[j]);
                    E1sum = E1sum + E1;
                    //System.out.println(E1);
                    E2 = (K2)*EPSILON* (Math.pow((SIGMA/distance[j]),12) - Math.pow((SIGMA/distance[j]),6));
                    E2sum = E2sum + E2;
                    //System.out.println(E2);
                    //System.out.println();
          //System.out.println(E1sum);
          //System.out.println();
          //System.out.println(E2sum);
          //System.out.println();
          double ETotal = (E1sum + E2sum) * Math.pow(10,-18);
     return ETotal;
     //checks the Total Temporary Energy between the randomly placed ions
     public static double checkTempEnergy (double tempDistance[], int numIons, double Q[]) {
          final double EPSILON = Math.sqrt(35.6*120), SIGMA = ((2.75+3.41)/2), K1 = 2.30, K2 = 0.0000552;
          double E1=0, E1sum=0, E2=0, E2sum=0;
          for (int i=1; i<numIons; i++) {     
               for (int j=0; j<i; j++) {     
                    E1 = (K1) * ((Q[j]*Q[i])/tempDistance[j]);
                    E1sum = E1sum + E1;
                    //System.out.println(E1);
                    E2 = (K2)*EPSILON* (Math.pow((SIGMA/tempDistance[j]),12) - Math.pow((SIGMA/tempDistance[j]),6));
                    E2sum = E2sum + E2;
                    //System.out.println(E2);
                    //System.out.println();
          //System.out.println(E1sum);
          //System.out.println();
          //System.out.println(E2sum);
          //System.out.println();
          double ETotal = (E1sum + E2sum) * Math.pow(10,-18);
     return ETotal;
     //MAIN METHOD!
public static void main(String[] args)
double side=0;
//Create the Cube and ask the user for how many Ions.
     //Number of Ions must be even for this program to converge/work.
     while (side<1.89){
          System.out.println("Choose length of one side of the Cube in Angstroms:");
          side = StdIn.readDouble();
          if (side<1.89){
          System.out.println("Side must be greater than Van der Waals radius of Argon, which is 1.88A.");
          System.out.println();
     System.out.println("The Volume of the Cube is: "+volCube(side));
     System.out.println();
     System.out.println("How many ions should there be in the Cube? Note: Odds are Na+ and Evens are Cl-");
     int numIons = StdIn.readInt();
     System.out.println();
     //Initialize and allocate memory for the Arrays...
     double arrayX[] = new double[numIons];
     double arrayY[] = new double[numIons];
     double arrayZ[] = new double[numIons];
     double tempX[] = new double[numIons];
     double tempY[] = new double[numIons];
     double tempZ[] = new double[numIons];
     int k=0;
     for (int j=1; j<numIons; j++){
          for (int i=0; i<j; i++) {
               k++;
     double distance[] = new double[k];
     double tempDistance[] = new double[k];
     double Q[] = new double[numIons];
     for (int i=0; i<numIons; i++){
          Q[i] = Math.pow(-1, (i+2));
     //Creates the initial random set of (x,y,z) coordinates
     for (int i=0; i != numIons; i++) {
          arrayX[i] = randomCoord(side);
          arrayY[i] = randomCoord(side);
          arrayZ[i] = randomCoord(side);
          System.out.println("Coordinates for ion "+(i+1)+" are: ");
          System.out.println("("+ arrayX[i]+ ","+ arrayY[i]+","+ arrayZ[i]+")");
     //check the distances between the ions
     System.out.println();
     System.out.println("Distances are: ");
     checkDistance(arrayX, arrayY, arrayZ, distance, numIons);
     int l=0;
     for (int i=0; i<k; i++){
          System.out.println(distance[l]+" is the distance "+ l);
          l++;
     System.out.println();
     //check the energy between the ions in their initial position
     System.out.println(checkEnergy(distance, numIons, Q)+" is in Joules!");
     System.out.println();
     //ask the User how many Trials
     System.out.println("How many Trials?");
     int numTrials = StdIn.readInt();
     System.out.println();
     //Create a new random set of (x,y,z) coordinates by taking a random Step between -1.88 and 1.88 Angstroms
     for (int i=0; i<numIons; i++) {
          double tinyStepX = ((double)(Math.random()*(3.76))- 1.88); //adds a random step between -1.88 and 1.88 Angstroms
          double tinyStepY = ((double)(Math.random()*(3.76))- 1.88);
          double tinyStepZ = ((double)(Math.random()*(3.76))- 1.88);
          tempX[i] = arrayX[i] + tinyStepX;
          tempY[i] = arrayY[i] + tinyStepY;
          tempZ[i] = arrayZ[i] + tinyStepZ;
          System.out.println("Coordinates for ion "+(i+1)+" are: ");
          System.out.println("("+ tempX[i]+ ","+ tempY[i]+","+ tempZ[i]+")");
     //check the distances between the ions in the new positions
     System.out.println();
     System.out.println("Distances are: ");
     checkTempDistance(tempX, tempY, tempZ, tempDistance, numIons);
     l=0;
     for (int i=0; i<k; i++){
          System.out.println(tempDistance[l]+" is the distance "+ l);
          l++;
     System.out.println();
     //check the energy of the randomly moved ions
     System.out.println(checkTempEnergy(tempDistance, numIons, Q)+" is in Joules!");
     System.out.println();
     if ((checkTempEnergy(tempDistance, numIons, Q)) < (checkEnergy(distance, numIons, Q))) {
          for (int i=0; i < numIons; i++) {
               arrayX[i] = tempX[i];
               arrayY[i] = tempY[i];
               arrayZ[i] = tempZ[i];
               distance[i] = tempDistance[i];
     System.out.println(checkEnergy(distance, numIons, Q)+" is in Joules!");
     System.out.println();
2. Once again, if you report an error you should indicate clearly the line that raises it. Once again you have failed to do this.Ok, my bad. The error is in line 200.
3.. One day you will realize the best way to get help is to write a SSCCE: [http://mindprod.com/jgloss/sscce.html]
My outputs are supposed to be random, so every output is different. But here is an example:
[http://i285.photobucket.com/albums/ll52/RommelTJ/FormingSalt2_help.jpg|http://i285.photobucket.com/albums/ll52/RommelTJ/FormingSalt2_help.jpg]
I am really sorry if I offended you or annoyed you in any way. I am just trying to get help and be nice. :(
Edited by: RommelTJ on Jun 18, 2008 2:38 PM