Error: cannot find symbol ArrayList
Do you have an import statement in the top of the file?
arraylist
How to create an 2D ArrayList in java?
I want to create a 2D array that each cell is an ArrayList! If you want to create a 2D array of ArrayList.Then you can do this :
How can I create an Array of ArrayLists?
As per Oracle Documentation: “You cannot create arrays of parameterized types” Instead, you could do: As suggested by Tom Hawting – tackline, it is even better to do:
Java ArrayList replace at specific index
I need help with this java please. I created an ArrayList of bulbs, and I’m trying to replace a bulb at specific index with another bulb. So with the following heading, how do I proceed?
HashSet vs. ArrayList
When its comes to the behavior of ArrayList and HashSet they are completely different classes. ArrayList ArrayList Does not validate duplicates. get() is O(1) contains() is O(n) but you have fully control over the order of the entries. get add contains next remove(0) iterator.remove ArrayList O(1) O(1) O(n) O(1) O(1) O(1) Not thread safe and to make it thread safe you have to use Collections.synchronizedList(…) HashSet … Read more
Why do I get an UnsupportedOperationException when trying to remove an element from a List?
Quite a few problems with your code: On Arrays.asList returning a fixed-size list From the API: Arrays.asList: Returns a fixed-size list backed by the specified array. You can’t add to it; you can’t remove from it. You can’t structurally modify the List. Fix Create a LinkedList, which supports faster remove. On split taking regex From the API: String.split(String regex): Splits this string around matches of the given regular expression. … Read more
Print ArrayList
I have an ArrayList that contains Address objects. How do I print the values of this ArrayList, meaning I am printing out the contents of the Array, in this case numbers. I can only get it to print out the actual memory address of the array with this code:
How to convert an ArrayList containing Integers to primitive int array?
You can convert, but I don’t think there’s anything built in to do it automatically: (Note that this will throw a NullPointerException if either integers or any element within it is null.) EDIT: As per comments, you may want to use the list iterator to avoid nasty costs with lists such as LinkedList:
how to iterate in List> in java and set their values as we do in a normal int a[i][j] matrix type [duplicate]
I think what you’re asking is how to do this: If you’re unfamiliar with lists in general, reading the answer here should provide valuable information on when to use which type of list
Java ArrayList copy
Yes, assignment will just copy the value of l1 (which is a reference) to l2. They will both refer to the same object. Creating a shallow copy is pretty easy though: (Just as one example.)