java howto ArrayList push, pop, shift, and unshift

I've determined that a Java ArrayList.add is similar to a JavaScript Array.push

I'm stuck on finding ArrayList functions similar to the following

• Array.pop
• Array.shift
• Array.unshift I'm leaning toward ArrayList.remove[At]

5 Answers

ArrayList is unique in its naming standards. Here are the equivalencies:

Array.push -> ArrayList.add(Object o); // Append the list Array.pop -> ArrayList.remove(int index); // Remove list[index] Array.shift -> ArrayList.remove(0); // Remove first element Array.unshift -> ArrayList.add(int index, Object o); // Prepend the list 

Note that unshift does not remove an element, but instead adds one to the list. Also note that corner-case behaviors are likely to be different between Java and JS, since they each have their own standards.

I was facing with this problem some time ago and I found java.util.LinkedList is best for my case. It has several methods, with different namings, but they're doing what is needed:

push() -> LinkedList.addLast(); // Or just LinkedList.add(); pop() -> LinkedList.pollLast(); shift() -> LinkedList.pollFirst(); unshift() -> LinkedList.addFirst(); 

maybe you want to take a look java.util.Stack class. it has push, pop methods. and implemented List interface.

for shift/unshift, you can reference @Jon's answer.

however, something of ArrayList you may want to care about , arrayList is not synchronized. but Stack is. (sub-class of Vector). If you have thread-safe requirement, Stack may be better than ArrayList.

Great Answer by Jon.

I'm lazy though and I hate typing, so I created a simple cut and paste example for all the other people who are like me. Enjoy!

import java.util.ArrayList; import java.util.List; public class Main { public static void main(String[] args) { List<String> animals = new ArrayList<>(); animals.add("Lion"); animals.add("Tiger"); animals.add("Cat"); animals.add("Dog"); System.out.println(animals); // [Lion, Tiger, Cat, Dog] // add() -> push(): Add items to the end of an array animals.add("Elephant"); System.out.println(animals); // [Lion, Tiger, Cat, Dog, Elephant] // remove() -> pop(): Remove an item from the end of an array animals.remove(animals.size() - 1); System.out.println(animals); // [Lion, Tiger, Cat, Dog] // add(0,"xyz") -> unshift(): Add items to the beginning of an array animals.add(0, "Penguin"); System.out.println(animals); // [Penguin, Lion, Tiger, Cat, Dog] // remove(0) -> shift(): Remove an item from the beginning of an array animals.remove(0); System.out.println(animals); // [Lion, Tiger, Cat, Dog] } } 

Underscore-java library contains methods push(values), pop(), shift() and unshift(values).

Code example:

import com.github.underscore.Underscore: List<String> strings = Arrays.asList("one", "two", " three"); List<String> newStrings = Underscore.push(strings, "four", "five"); // ["one", " two", "three", " four", "five"] String newPopString = Underscore.pop(strings).fst(); // " three" String newShiftString = Underscore.shift(strings).fst(); // "one" List<String> newUnshiftStrings = Underscore.unshift(strings, "four", "five"); // ["four", " five", "one", " two", "three"]