Hi, Im making a space invaders type game, but I cant get the bullets to delay (for a second) between shots, if the key is held down, there is just a stream of bullets. How can I do this?

Plane plane;
Bullet[] bullet;
int maxBullets = 5000;
int time;
int lastSec;
int counter;


void setup(){

 plane = new Plane(8);
 bullet = new Bullet[maxBullets];
 for(int i = 0; i< maxBullets; i++)
 {
   bullet[i] = new Bullet();
   bullet[i].positionY = 2;
 }
}

void draw(){

 int s = second();
 time = s;


 background(200);



 plane.display();



 for(int i = 0; i < maxBullets; i++){
   if(bullet[i].alive){
     bullet[i].display();
     bullet[i].positionY++;
   }
 }


 for(int i = 1; i< maxBullets ;i++){
   if(!bullet[i].alive){
     if(keyPressed) {
       if(key == 'a'){

         int timer = s;
         bullet[i].alive = true;
         bullet[i].positionX = plane.positionX;
         i++;
         counter ++;
         println(counter);
         return;
       }
     }
   }
 }
}



class Plane{
 
 int planeHeight;
 int positionX;
 
Plane(int planeHeight){
 
 this.planeHeight = planeHeight;
}

void display(){
 rect(positionX,90,10,planeHeight);
 
   if(keyPressed) {
   if(key == 'z'){
     plane.positionX--;
   }
 }

   if(keyPressed) {
   if(key == 'x'){
     plane.positionX++;
   }
 }
}  
}



class Bullet{
 
 boolean alive;
 int positionX;
 int positionY;
 int velocity;
 
 Bullet(){
   alive = false;
 }

 void display(){
   ellipse(positionX,positionY,5,5);
 }  
}

for games i like to just use processings ability to set the framerate in the setup method. then when a shot is fired just record the framecount. then in your if statement check to see if the current framecount is >= the old framecount + x (where x is the delay) I find it works well to do 30 frames per second. you could impement different weapons that have different delays this way also to get different firing rates.