List in Java

Just like shopping list

Class Diagram (click to zoom)

read more here

imports

import java.util.List;
import java.util.ArrayList;

Array List

Array List is one of the inbuilt data structures in Java. It is a dynamic array (where the size of the data structure not needed to be declared first) for storing elements (Objects).

Creating a List

List<String> strings;
List<Double> doubles;

If you try to add something to the lists above you will get a NullPointerException, because strings and doubles, both equal null!

List<T> myArrayList = new ArrayList<>();
List<T> myLinkedList = new LinkedList<>();

Positional Access Operations

add(T type)
add(int index, T type)
remove(Object o)
remove(int index)
get(int index)
set(int index, E element)
int indexOf(Object o)
int lastIndexOf(Object o)

Iterating over the List

public void printEachElement(List<String> list){
    for(String s : list){
        System.out.println(s);
    }
}

To add an element

myArrayList.add(element);
myArrayList.add(index, element); 
//index of the element should be an int (starting from 0)

To remove

myArrayList.remove(element);
myArrayList.remove(index); 
//index of the element should be an int (starting from 0)

• Removing elements from list B that are present in the list A

numbersB.removeAll(numbersA);
    System.out.println("B cleared: " + numbersB);