java howto ArrayList push, pop, shift, and unshift
JavaArraylistJava Problem Overview
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 towardArrayList.remove[At]
Java Solutions
Solution 1 - Java
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.
Solution 2 - Java
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();
Solution 3 - Java
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.
Solution 4 - Java
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]
}
}
Solution 5 - Java
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"]