How do i split an arraylist of string into multiples of 8?

timhua

I have an arraylist of strings that contains values of 0 and 1. I want to split the arraylist to multiples of 8 and store them seperately in another arraylist. For example, i have a arraylist of 0 and 1s. I take the first 8 digits then store in array, then the next 8 store into second index of the second array. If that makes any sense.

I have seen the split() function but I haven't figured out using on an arraylist.

KevinWorkman

You can't.

Just use a for loop and split it however you want.

timhua

its more clear if i rephrase my question as. How do i split an arraylist at every nth position and store in an array?

Example

Input - ArrayList = [0,1,1,0,1,0,1,0,1,0,1,0,0,0,1,1,0]

if n = 8, i take every nth position and store into array so

Output - Array =[011010101, 01000110]

TfGuy44

//Array of ints
int[] in = {0,1,1,0,0,0,1,1,
            1,1,1,1,1,1,0,0,
            1,0,1,0,1,0,1,0};
String[] out = new String[in.length/8];
int j = -1;
for(int i = 0; i < out.length; i++) out[i] = "";
for(int i = 0; i < in.length; i++){
  if(i%8==0) j++;
  //println("i="+i+" j="+j);
  out[j] = out[j] + char('0'+in[i]);
  //println("out["+j+"]="+out[j]);
}
for(int i = 0; i < out.length; i++) println( out[i] );

timhua

thanks TfGuy44 for the reply but can i ask what does char('0'+in[i]); means?

TfGuy44

println( "1) " + char(0) );
println( "2) " + char('0') );
println( "3) " + int('0') );
println( "4) " + char(48) );
println( "5) " + char(49) );
println( "6) " + char('0'+0) );
println( "7) " + char('0'+1) );

GoToLoop

My more complicated solution too. A little l8 for the party it seems: :O)

/**
 * UnifyStringListAsArray (v1.02)
 * by  GoToLoop (2015/Feb/24)
 * for Timhua
 * 
 * forum.processing.org/two/discussion/9566/
 * how-do-i-split-an-arraylist-of-string-into-multiples-of-8
 */

static final String[] unifyStringListAsStringArray(StringList list, int n) {
  if (list == null || list.size() == 0 || n < 1)  return new String[0];

  int len = list.size(), seqs = 1 + (len-1)/n; // js: seqs = 1 + (0 | (len-1)/n);
  String[] joined  = new String[seqs];
  StringBuilder sb = new StringBuilder(n);

  for (int i = 0; i < len; i += n) {
    for (int j = i, qty = min(j + n, len); j != qty; sb.append(list.get(j++)));
    joined[i/n] = sb.toString(); // js: joined[i/n | 0] = sb.toString();
    sb.delete(0, sb.length());
  }

  return joined;
}

static final int SPLIT = 8;

final StringList myList = new StringList(new String[] {
  "0", "1", "1", "0", "1", "0", "1", "0",
  "1", "0", "1", "0", "0", "0", "1", "1",
  "0", "1", "0"
});

String[] result;

void setup() {
  println(myList, '\n');
  result = unifyStringListAsStringArray(myList, SPLIT);
  println(result);
  exit();
}

timhua

GoToLoops it does seem more complicated :)) i'll try to slowly dissect your code thanks for reply

timhua

I get an error called "The method parseChar(byte) is the type PApplet is not application for the arguments (String)"

What does this mean?

GoToLoop

• AFAIK, my code sample works in any Processing 2.1.x family and on!
• I'm currently using 64-bit Processing version 2.2.1 now @ Lubuntu Linux.
• Error message means that datatype byte isn't acceptable for PApplet's parseChar() method.

GoToLoop

• I've noticed that in @TfGuy44's code an int[] is used as source.
• I remember you specified yours was an ArrayList of String objects.
• That's why in my own I've used a similar structure called StringList instead:
  http://processing.org/reference/StringList.html
• Now I've modified unifyStringListAsStringArray() to accept a byte[] now.
• If you prefer int[] or char[], etc., just a matter of replacing those byte[] declarations w/ it.
• It's renamed to unifyByteArrayAsStringArray(). Also changed for () to while (). Check it out!
• Any doubts about it just ask! :>

/**
 * unifyByteArrayAsStringArray (v1.11)
 * by  GoToLoop (2015/Feb/25)
 * for Timhua
 * 
 * forum.processing.org/two/discussion/9566/
 * how-do-i-split-an-arraylist-of-string-into-multiples-of-8
 */

static final String[] unifyByteArrayAsStringArray(byte[] arr, int n) {
  if (arr == null || arr.length == 0 || n < 1)  return new String[0];

  int i = 0, len = arr.length, seqs = 1 + (len-1)/n; // js: seqs = 1 + (0 | (len-1)/n);
  String[] joined  = new String[seqs];
  StringBuilder sb = new StringBuilder(n);

  while (i != len) {
    int qty = min(i + n, len);
    while (i != qty)  sb.append(arr[i++]);
    joined[(i-1)/n] = sb.toString(); // js: joined[i/n | 0] = sb.toString();
    sb.delete(0, sb.length());
  }

  return joined;
}

static final int SPLIT = 8;

final byte[] myArray = {
  0, 1, 1, 0, 1, 0, 1, 0,
  1, 0, 1, 0, 0, 0, 1, 1,
  0, 1, 0
};

String[] result;

void setup() {
  println(myArray);
  println();
  result = unifyByteArrayAsStringArray(myArray, SPLIT);
  println(result);
  exit();
}

timhua

GoToLoops I dont quite understand this piece of code that you coded can you explain it to me?

  int i = 0, len = arr.length, seqs = 1 + (len-1)/n;
  String[] joined  = new String[seqs];
  StringBuilder sb = new StringBuilder(n);
 
  while (i != len) {
    int qty = min(i + n, len);
    while (i != qty)  sb.append(arr[i++]);
    joined[(i-1)/n] = sb.toString();
    sb.delete(0, sb.length());
  }
 
  return joined;

GoToLoop

Actually I dunno whether your doubts are related to StringBuilder class or the algorithm itself! :-/
You can read about StringBuilder class below:
https://docs.oracle.com/javase/8/docs/api/java/lang/StringBuilder.html

StringBuilder was chosen for performance reasons.
Regular String w/ the + concatenator operator yield the same results:
http://processing.org/reference/addition.html

Simpler String w/ += concatenation version:

static final String[] unifyByteArrayAsStringArray(byte[] arr, int n) {
  if (arr == null || arr.length == 0 || n < 1)  return new String[0];

  int i = 0, len = arr.length, seqs = 1 + (len-1)/n;
  String[] joined = new String[seqs];
  String s = "";

  while (i != len) {
    int qty = min(i + n, len);
    while (i != qty)  s += arr[i++];
    joined[(i-1)/n] = s;
    s = "";
  }

  return joined;
}

Compare the above w/ the original StringBuilder version here:

static final String[] unifyByteArrayAsStringArray(byte[] arr, int n) {
  if (arr == null || arr.length == 0 || n < 1)  return new String[0];

  int i = 0, len = arr.length, seqs = 1 + (len-1)/n;
  String[] joined  = new String[seqs];
  StringBuilder sb = new StringBuilder(n);

  while (i != len) {
    int qty = min(i + n, len);
    while (i != qty)  sb.append(arr[i++]);
    joined[(i-1)/n] = sb.toString();
    sb.delete(0, sb.length());
  }

  return joined;
}

If it's something else, please point where it is so I can explain it! :-bd