Usually it repeats the last 7 elements (values) in my arraylist.

Why does this happen, any idea? Is it always 7 elements being repeated or can the number vary?

This happens because im analysing the entropy of a  wolfram celular automata, and that cellular automata tends to stabilize in time, it starts producing complex behaivor but after some time it arrives to a point where it repeat the same 7 lines (so it repeats the last 7 values over and over), when that happens i need to detect that in order to change some states in the cells in order to have an infinite pattern.

In the following code, when the cellular automata stabilizes , you can click over the processing window to change the state of the cells .  I would like to do it automatically

here is the code:

1. import java.util.*;
2. 
   
3. CA ca;
4. 
   
5. public double calculateShannonEntropy(String[] values) {
6.   Map<String, Integer> map = new HashMap<String, Integer>();
7.   // count the occurrences of each value
8.   for (String sequence : values) {
9.     if (!map.containsKey(sequence)) {
10.       map.put(sequence, 0);
11.     }
12.     map.put(sequence, map.get(sequence) + 1);
13.   }
14.   // calculate the entropy
15.   double result = 0.0d;
16.   for (String sequence : map.keySet()) {
17.     double frequency = (double) map.get(sequence) / values.length;
18.     result -= frequency * (Math.log(frequency) / Math.log(2));
19.   }
20.   return result;
21. }
22.  
23. void setup() {
24.   size(200, 200, P2D);
25.   frameRate(12);
26.   ca = new CA( new int[] { 0, 1, 1, 0, 1, 1, 1, 0 } );
27.   background(0);
28.   noStroke();
29. }
30. 
    
31. void draw() {
32.   ca.render();
33.   ca.generate();
34.   
35.   if (ca.finished()) {
36.     background(0);
37.     ca.restart();
38. }
39. }
40. 
    
41. 
    
42. void mouseClicked() {
43.   
44.    ca.click ();
45.    ca.printon();
46. 
    
47. }
48.  
49. class CA {
50.   int[] cells, rules;
51.   int generation, scl;
52.   ArrayList entropias;
53.   String stri[] = new String[199] ;   //aca voy a poner los caracteres resultantes 
54.   String junto ;    // aca pongo mis caracteres unidos.
55.     
56.   CA(int[] r) {
57.     rules = r;
58.     scl = 1;
59.     cells = new int[width/scl];
60.     
61.     entropias = new ArrayList();  // Create an empty ArrayList
62.  
63.    for (int i = 1; i < cells.length-1; i++) {
64.      cells[i] = int(random(2));
65.   
66.     }
67.  }
68.   
69.   void restart() {
70.     generation = 0;
71.   }
72.   
73.   
74.   void click(){
75.   // cells[94] = 1;
76.   cells[int(random(200))] = int(random(2));
77.    }
78.   
79.   void generate() {
80.     int[] nextgen = new int[cells.length];
81.     for (int i = 1; i < cells.length-1; i++) {
82.       int left = cells[i-1];
83.       int me = cells[i];
84.       int right = cells[i+1];
85.       nextgen[i] = rules(left, me, right);
86.     }
87.     cells = (int[]) nextgen.clone();
88.    
89.     stri = str(cells);
90.     
91.     String junto = join(stri , "");
92.     generation++;
93.        
94.    String [] sa = new String[junto.length() - 1];
95.   //println("THe collection of values we want to");
96.   //println("calculate the entropy for");
97.   for (int i = 0; i < sa.length; i++) {  
98.     sa[i] = junto.substring(i, i+2);
99.    // println(sa[i]);
100.   }
101.   // The method returns a double need to cast to a float
102.   float entropy = (float) calculateShannonEntropy(sa);
103.   
104.  entropias.add(entropy); 
105.   //  println(entropias);
106.   
107.    if (entropy < 1.6 ){
108.     cells[int(random(200))] = int(random(2));  
109.   }
110. }
111.   
112.   void printon() 
113.   {
114.    println(entropias); 
115.    }
116. 
     
117.   void render() {
118.     for (int i = 0; i < cells.length; i++) {
119.       fill(cells[i] == 1 ? 255 : 0);
120.       rect(i*scl, generation*scl, scl, scl);
121.     }
122.   }
123.   
124.   int rules (int a, int b, int c) {
125.     if (a == 1 && b == 1 && c == 1) return rules[0];
126.     if (a == 1 && b == 1 && c == 0) return rules[1];
127.     if (a == 1 && b == 0 && c == 1) return rules[2];
128.     if (a == 1 && b == 0 && c == 0) return rules[3];
129.     if (a == 0 && b == 1 && c == 1) return rules[4];
130.     if (a == 0 && b == 1 && c == 0) return rules[5];
131.     if (a == 0 && b == 0 && c == 1) return rules[6];
132.     if (a == 0 && b == 0 && c == 0) return rules[7];
133.     return 0;
134.   }
135.   
136.   boolean finished() {
137.     return generation > height/scl;
138.   }
139. }
140. 
     
141.