No. An ArrayList can be empty (or with nulls as items) an not be null. It would be considered empty. You can check for am empty ArrayList with: ArrayList arrList = new ArrayList(); if(arrList.isEmpty()) { // Do something with the empty list here. } Or if you want to create a method that checks for … Read more
In Java 8 Use below code:- Optional.ofNullable(listToBeAdded).ifPresent(listToBeAddedTo::addAll) listToBeAdded – The list whose elements are to be added. listToBeAddedTo – The list to which you are adding elements using addAll.
ArrayList<String> aList = new ArrayList<String>(Arrays.asList(question1)); aList.addAll(Arrays.asList(question2));
Collections.sort(teamsName.subList(1, teamsName.size())); The code above will reflect the actual sublist of your original list sorted.
You’re synchronizing twice, which is pointless and possibly slows down the code: changes while iterating over the list need a synchronnization over the entire operation, which you are doing with synchronized (in_queue_list) Using Collections.synchronizedList() is superfluous in that case (it creates a wrapper that synchronizes individual operations). However, since you are emptying the list completely, … Read more
Just use a traditional for loop: for (int i = 0; i < yourArrayList.size(); i ++) { // i is the index // yourArrayList.get(i) is the element }
You could write a custom comparator: Collections.sort(list, new Comparator<String>() { public int compare(String a, String b) { return Integer.signum(fixString(a) – fixString(b)); } private int fixString(String in) { return Integer.parseInt(in.substring(0, in.indexOf(‘_’))); } });
Collections.addAll is what you want. Collections.addAll(myArrayList, ‘+’, ‘-‘, ‘*’, ‘^’); Another option is to pass the list into the constructor using Arrays.asList like this: List<Character> myArrayList = new ArrayList<Character>(Arrays.asList(‘+’, ‘-‘, ‘*’, ‘^’)); If, however, you are good with the arrayList being fixed-length, you can go with the creation as simple as list = Arrays.asList(…). Arrays.asList … Read more
Go through every element in the Cursor, and add them one by one to the ArrayList. ArrayList<WhateverTypeYouWant> mArrayList = new ArrayList<WhateverTypeYouWant>(); for(mCursor.moveToFirst(); !mCursor.isAfterLast(); mCursor.moveToNext()) { // The Cursor is now set to the right position mArrayList.add(mCursor.getWhateverTypeYouWant(WHATEVER_COLUMN_INDEX_YOU_WANT)); } (replace WhateverTypeYouWant with whatever type you want to make a ArrayList of, and WHATEVER_COLUMN_INDEX_YOU_WANT with the column index … Read more
The main difference between both implementation is the resize strategy ArrayList is resized to a new size of oldCapacity + (oldCapacity >> 1), resulting in an increse of ~50%. The default capacity is 10, resulting in a capacities after resize of 15, 22, 33, 49, 73, 109, 163, 244, 366… ArrayDeque is always resized to … Read more