You can set the initial size for an ArrayList by doing ArrayList<Integer> arr=new ArrayList<Integer>(10); However, you can’t do arr.add(5, 10); because it causes an out of bounds exception. What is the use of setting an initial size if you can’t access the space you allocated? The add function is defined as add(int index, Object element) … Read more
Say I create one object and add it to my ArrayList. If I then create another object with exactly the same constructor input, will the contains() method evaluate the two objects to be the same? Assume the constructor doesn’t do anything funny with the input, and the variables stored in both objects are identical. ArrayList<Thing> … Read more
This question’s answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions. I have an ArrayList that I want to output completely as a String. Essentially I want to output it in order using the toString of each element separated by tabs. Is there … Read more
I have an ArrayList with custom objects. Each custom object contains a variety of strings and numbers. I need the array to stick around even if the user leaves the activity and then wants to come back at a later time, however I don’t need the array available after the application has been closed completely. … Read more
What is the simplest way to reverse this ArrayList? ArrayList<Integer> aList = new ArrayList<>(); //Add elements to ArrayList object aList.add(“1”); aList.add(“2”); aList.add(“3”); aList.add(“4”); aList.add(“5”); while (aList.listIterator().hasPrevious()) Log.d(“reverse”, “” + aList.listIterator().previous()); 12 Answers 12
I’m trying to convert an ArrayList containing Integer objects to primitive int[] with the following piece of code, but it is throwing compile time error. Is it possible to convert in Java? List<Integer> x = new ArrayList<Integer>(); int[] n = (int[])x.toArray(int[x.size()]); 19 Answers 19
This question already has answers here: Initialization of an ArrayList in one line (33 answers) Closed 5 years ago. Is there a Utility method somewhere that can do this in 1 line? I can’t find it anywhere in Collections, or List. public List<String> stringToOneElementList(String s) { List<String> list = new ArrayList<String>(); list.add(s); return list; } … Read more
This question already has answers here: Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop (30 answers) Closed 7 years ago. I’m trying to remove some elements from an ArrayList while iterating it like this: for (String str : myArrayList) { if (someCondition) { myArrayList.remove(str); } } Of course, I get a … Read more
What are the differences between the two data structures ArrayList and Vector, and where should you use each of them? 7 Answers 7
I have a List of doubles in java and I want to sort ArrayList in descending order. Input ArrayList is as below: List<Double> testList = new ArrayList(); testList.add(0.5); testList.add(0.2); testList.add(0.9); testList.add(0.1); testList.add(0.1); testList.add(0.1); testList.add(0.54); testList.add(0.71); testList.add(0.71); testList.add(0.71); testList.add(0.92); testList.add(0.12); testList.add(0.65); testList.add(0.34); testList.add(0.62); The out put should be like this 0.92 0.9 0.71 0.71 0.71 0.65 … Read more