Hi there!
I'm kind of new to processing. I took L-system example from Learning\Examples. I've tried to add some slider to control iterations and angle. When i have a lot of string in RuleA, the program is not respond.
So, I have tried to check in the function. I guess the problem happened in simulate function. The second problem, when I try to change the number of iterations on the slider (let's say 4 iterations), the program is take a long time to calculate(very slow). So, anybody knows how to fix this.

import controlP5.*;   LSystem ps; ControlP5 controlP5; int iterations = 2; float angle = 360; void setup()   {  size(700, 700);  frameRate(24);    controlP5 = new ControlP5(this);  controlP5.addSlider("iterations",0,9,iterations,20,420,20,100);  controlP5.addSlider("Angle",1,360,angle,20,550,20,100);  ps = new LSystem();  ps.simulate(iterations,2); } public void iterations(int newIteration) {  ps.reset();  ps.simulate(newIteration,newIteration); } public void Angle(float newAngle) {  //ps.reset();   angle = newAngle; } void draw()   {  stroke(255);  background(0);  ps.render(); smooth(); } class LSystem {  int steps = 0;  int step_inc = 1;  String axiom;  String ruleA;  String ruleB;  String production;  float startLength;  float drawLength;  float theta;  int generations;  LSystem() {    axiom = "F+F";    ruleA = "+F+F-F-F+F+F+F+F+F+F+F-F-F-F-F ";  //Let's say I have a lot of string here!(may be 100)    ruleB = "F-F-F+FF";    startLength = 130.0f;    theta = radians(1);        reset();  }  void reset() {    production = axiom;    drawLength = startLength;    generations = 0;    steps = 0;  }  int getAge() {        return generations;      }      void render() {    pushMatrix();    translate(width/2, height/2);    steps += step_inc;              if (steps > production.length()) {      steps = production.length();          }    for (int i = 0; i < steps; i++) {      char step = production.charAt(i);      if ((step == 'F') || (step == 'B')) {        fill(255,20);        line(0, 0, drawLength, 0);        translate(drawLength, 0);      }        else if (step == '+') {        rotate(-theta*angle);      }        else if (step == '-') {        rotate(+theta*angle);            }      }    popMatrix();  }    void simulate(int gen, int step_inc_) {    while (getAge() < gen) {            production = iterate(production, ruleA, ruleB);          }    step_inc = step_inc_;  }  String iterate(String prod_, String ruleA_, String ruleB_) {    drawLength = drawLength * 0.6;    generations++;    String newProduction = "";              for (int i = 0; i < prod_.length(); i++) {       if (prod_.charAt(i) == 'F') {         println("******"+generations+"  "+prod_.length());         newProduction += ruleA_; //       } else if (prod_.charAt(i) == 'B') { //         newProduction += ruleB_;       } else {         newProduction += prod_.charAt(i);       }    }    return newProduction;      } }

This is what I have tried but it's doesn't work well..
******************************************************

String iterate(String prod_, String ruleA_, String ruleB_) {
   drawLength = drawLength * 0.6;
   generations++;
   
//    char[] c=new char[prod_.length()*ruleA_.length()];
//    char[] ruleAChar=ruleA_.toCharArray();
//    String newProduction=new String(c);
//    c=null;
//    int index=0;
   String newProduction = "";          
   for (int i = 0; i < prod_.length(); i++) {
      if (prod_.charAt(i) == 'F') {
//        
//
//         for(int j=0;j<ruleAChar.length;j++){
//           c[j+index]=ruleAChar[j];
//         }
//         index=index+ruleAChar.length;
//   println("******"+generations+"  "+index+"  "+prod_.length());

        newProduction += ruleA_;

      } else {
//         c[index] = prod_.charAt(i);
//         index++;
        newProduction += prod_.charAt(i);
      }
   }
   return newProduction;
//char c2[]=new char[index];
//println(index+"  "+c.length);
//for(int i=0;i<c2.length;i++)
//  c2[i]=c[i];
//  
//  c=null;
//
//return (new String(c2));
 }
}

thanks
patty