java - What is the "ConcurrentModificationException"? -

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• iterating through collection, avoiding concurrentmodificationexception when removing in loop 16 answers

this bullets class

package mainpackage;  import java.awt.graphics; import java.awt.image.bufferedimage;  public class bullets {      private double x;     private double y;     private bufferedimage bulletimage;     bullets(double x, double y){         this.x = x;         this.y = y;         imageloader loader = new imageloader();         spritesheet ss = new spritesheet(loader.loadimage("/pics/thespritesheet.png"));         bulletimage = ss.grabimage(2, 1, 32, 32);     }      public void render(graphics g){         g.drawimage(bulletimage, (int)x, (int)y, null);     }     public void tick(){         y--;     }     public double getx(){         return x;     }     public double gety(){         return y;     } } 

then made bulletqualities class

package mainpackage;  import java.awt.graphics; import java.util.linkedlist;  public class bulletqualities {     bullets b;     private linkedlist<bullets> bulletlist = new linkedlist<bullets>();      public void addbullet(bullets b){         bulletlist.add(b);     }     public void tick(){ 

i error on next line

        for(bullets bullet:bulletlist){                 if(bullet.gety() == 0)                 removebullet(bullet);             bullet.tick();         }     }     public void render(graphics g){         for(int x = 0;x < bulletlist.size(); x++){             bulletlist.get(x).render(g);         }     }     public void removebullet(bullets bullet){         bulletlist.remove(bullet);     } } 

this error message:

exception in thread "thread-4" java.util.concurrentmodificationexception     @ java.util.linkedlist$listitr.checkforcomodification(unknown source)     @ java.util.linkedlist$listitr.next(unknown source) 

then showed lines errors. have no idea why it's not working. please me. mean lot. :-)

oh, forgot, removebullet method bulletqualities class:

public void removebullet(bullets bullet){     bulletlist.remove(bullet); } 

you getting exception because of removing element while iterating list.

for(bullets bullet:bulletlist){                 if(bullet.gety() == 0)                 removebullet(bullet);  // removing element during iteration.             bullet.tick();         } 

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