Hi again. I'm trying to find a way to draw lines within a for loop but i'm having a problem doing this none of my lines show up can some one take a look at the code and let me know whats going on. I've noted the part where i'm having the problem.

import traer.physics.*;

ParticleSystem physics;
Particle[][] particles;
Spring[][] springs;
int gridSize = 20;

void setup()
{
 size(800, 800);
 smooth();
 fill(0);
 framerate(60);
 
   physics = new ParticleSystem(0, 0,20,0.5);
 
 particles = new Particle[gridSize][gridSize];
 springs = new Spring[gridSize][gridSize];
 
 float gridStepX = (float) ((width / 2) / gridSize);
 float gridStepY = (float) ((height / 2) / gridSize);
 
 for (int i = 0; i < gridSize; i++)
 {
   for (int j = 0; j < gridSize; j++)
   {
//Spring makeSpring( Particle a, Particle b, float strength, float damping, float restLength )
particles[i][j] = physics.makeParticle(0.2, j * gridStepX + (width / 4), i * gridStepY + 20, 0);
if (j > 0)
{
 springs[i][j] = physics.makeSpring(particles[i][j - 1], particles[i][j], 1.0, 0.5, sin(i)+30 );
}
   }
 }
 
 for (int j = 0; j < gridSize; j++)
 {
   for (int i = 1; i < gridSize; i++)
   {
 physics.makeSpring(particles[i - 1][j], particles[i][j], 1, 0.5, 20);
   }
 }
 for (int a = 0; a < gridSize; a++)
{
 float f = random(20);
 int b = int(f);
 particles[a][0].makeFixed();
 particles[0][a].makeFixed();
 particles[gridSize-1][a].makeFixed();
 particles[a][gridSize-1].makeFixed();
 //add switch loop to stop if value exceeds gridsize then try to use complex sequence to fix points
 particles[a][a].makeFixed();

}
//array of spring tension/compression store info for all springs and color_code
 //convert_type


//This is where I get the error!!!!!!!!!!





// end of the part I added that caused the error.

}

void draw()
{
 
 
 
 ////start of error part
 
   for (int y = 1; y < gridSize-1; y++)
 {
   for (int t = 1; t < gridSize-1; t++)
   {
int[] compressTest = new int[gridSize];
println("y="+y+" t="+t);
float stress = springs[y][t].restLength();  
int stressInt = int(stress);
println(stressInt);
compressTest[t] = stressInt;  
println("spring rest length is equal to " + compressTest[t]);
float compressTest2 = springs[y][t].currentLength();  
println("spring2 actual length is equal to " + compressTest2);
if ( stressInt < compressTest2 ){
   stroke(0, 255, 0);
 line(particles[y][t].position().x(),particles[y][t].position().y(), particles[y+1][t+1].position().x(),particles[y+1][t+1].position().y() );
 springs[y][t].turnOff();
}
if (compressTest2 < stressInt ){
 stroke(255, 0, 0);
 line(particles[y][t].position().x(),particles[y][t].position().y(), particles[y+1][t+1].position().x(),particles[y+1][t+1].position().y() );
 springs[y][t].turnOn();
}
   }
 }
 
 
 ///end of error part
 
 
 
 
 
 physics.advanceTime(0.1);
 
 if (mousePressed)
 {
   particles[0][gridSize - 1].moveTo(mouseX, mouseY, 0);
   particles[0][gridSize - 1].velocity().clear();
 }
 
 background(255);
 


}

void mouseReleased()
{
 particles[0][gridSize - 1].setVelocity( (mouseX - pmouseX), (mouseY - pmouseY), 0 );
}