How to iterate through an ArrayList of Objects of ArrayList of Objects

Question

Using an example   Let say I have a class call Gun  I have another class call Bullet   Class Gun has an ArrayList of Bullet   To iterate through the Arraylist of Gun   instead of doing this   ArrayList lt Gun gt  gunList   new ArrayList lt Gun gt     for  int x 0  x lt gunList size    x        System out println gunList get x      We can simply iterate through the ArrayList of Gun as such   for  Gun g  gunList  System out println g      Now  I want to iterate and print out all Bullet of my 3rd Gun object   for  int x 0  x lt gunList get 2  getBullet   size    x       getBullet is just an accessor method to return the arrayList of Bullet      System out println gunList get 2  getBullet   get x      Now my question is  Instead of using the conventional for-loop  how do I printout the list of gun objects using the ArrayList iteration

User · Answer

When using Java8 it would be more easier and a single liner only       gunList get 2  getBullets   forEach n - gt  System out println n

User · Answer

Edit   Well  he edited his post   If an Object inherits Iterable  you are given the ability to use the for-each loop as such   for Object object   objectListVar           code here     So in your case  if you wanted to update your Guns and their Bullets   for Gun g   guns           invoke any methods of each gun      ArrayList lt Bullet gt  bullets   g getBullets        for Bullet b   bullets              System out println  X      b getX        Y      b getY                 update  check for collisions  etc              First get your third Gun object   Gun g   gunList get 2     Then iterate over the third gun s bullets   ArrayList lt Bullet gt  bullets   g getBullets     for Bullet b   bullets           necessary code here

User · Answer

You want to follow the same pattern as before   for  Type curInstance  CollectionOf lt Type gt          use currInstance     In this case it would be   for  Bullet bullet   gunList get 2  getBullet         System out println bullet

User · Answer

int i   0     Counter used to determine when you re at the 3rd gun for  Gun g   gunList       For each gun in your list     System out println g      Print out the gun     if  i    2       If you re at the third gun         ArrayList lt Bullet gt  bullets   g getBullet       Get the list of bullets in the gun         for  Bullet b   bullets       Then print every bullet             System out println b                 i       Don t forget to increment your counter so you know you re at the next gun

User · Answer

for  Bullet bullet   gunList get 2  getBullet    System out println bullet

User · Answer

We can do a nested loop to visit all the elements of elements in your list    for  Gun g  gunList       System out print g toString       n           for Bullet b   g getBullet           System out print g               System out println

[java] How to iterate through an ArrayList of Objects of ArrayList of Objects?

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