Key Concepts

Review core concepts you need to learn to master this subject

ArrayLists

LinkedLists

HashMaps

Sets

ArrayLists

// Create an ArrayList that stores Strings:
ArrayList<String> months = new ArrayList<String>();

// Add values to the end of the ArrayList:
months.add("January");
months.add("March");

// Add values to a specified index in the ArrayList:
months.add(1, "February");

// Access a value from the ArrayList:
System.out.println(months.get(0)); // Prints: January

// Remove a value from the ArrayList:
months.remove("February");
months.remove(0); // Removes the zeroeth element

An ArrayList is a built-in data structure that uses a dynamic array to store its elements.

In order to use this data structure, you must import java.util.ArrayList at the top of your program.