Copying Multiple Arrays into One Large Array

Question

I'm currently trying to copy multiple character arrays into one larger character array in a method that prints data gathered from a database. Here is my code:
private static void printData(String[] data){
        try {
            int totalLengthOfAllStrings = 0;
            for(int i = 0; i < data.length; i++) {
                data[i] += '\n';
                totalLengthOfAllStrings += data.length();
int runningLength = 0;
char[] printArray = new char[totalLengthOfAllStrings];
for(int j = 0; j < data.length; j++) {
char[] tempArray = data[j].toCharArray();
runningLength += tempArray.length;
System.arraycopy(tempArray, 0, printArray, runningLength - 1, tempArray.length);
DocFlavor df = DocFlavor.CHAR_ARRAY.TEXT_PLAIN;
Doc printDoc = new SimpleDoc(printArray, df, null);
PrintRequestAttributeSet aset = new HashPrintRequestAttributeSet();
aset.add(new Copies(1));
aset.add(MediaSize.NA.LETTER);
aset.add(Sides.DUPLEX);
PrintService[] services = PrintServiceLookup.lookupPrintServices(df, aset);
if (services.length > 0) {
DocPrintJob job = services[0].createPrintJob();
try {
job.print(printDoc, aset);
System.out.println("Print successful!");
catch (PrintException pe) {
catch(Exception e) {
e.printStackTrace();
I keep getting an ArrayIndexOutOfBoundsException and for the life of me I can't figure out why.
Can anyone help with this?
Thanks!
-Matt

Answer 1

I think your problem lies with the second for loop:
for(int j = 0; j < data.length; j++)  {
    char[] tempArray = data[j].toCharArray();
    runningLength += tempArray.length;
    System.arraycopy(tempArray, 0, printArray, runningLength - 1, tempArray.length);
}If I am not wrong, you should swap the sequence of the runningLength and System.arraycopy statements, and also move the minus 1 from arraycopy statement to the runningLength statement. The result would look like this:
for(int j = 0; j < data.length; j++)  {
    char[] tempArray = data[j].toCharArray();
    System.arraycopy(tempArray, 0, printArray, runningLength, tempArray.length);    // swapped and removed the -1
    runningLength += tempArray.length - 1;    // swapped and appended the -1
}The main reason for these changes is because when j == data.length - 1, the value of runningLength would have already exceeded the size of printArray. Therefore, swapping the position would be able to overcome this problem.