Arrays and ArrayLists

Students easily confuse the two. The tradeoffs between them is worth noting.

Arrays  ArrayLists
Subscripting operator for access is convenient Only access is through instance methods
Length cannot be changed once created Grows and shrinks with additions and subtractions
(Fast performance due to primitive implementation) (Slower performance due to method call overhead)

A comparison via simple example:

Array  ArrayList
String[] students = new String[4];
students[0] = "John";
students[1] = "Paul";
students[2] = "George";
students[3] = "Ringo";
for(int i = 0; i < students.length; i++) {
    System.out.println(students[i]);
}

ArrayList students = new ArrayList();
students.add("John");
students.add("Paul");
students.add("George");
students.add("Ringo");
for(int i = 0; i < students.size(); i++) {
    String name = (String) students.get(i);
    System.out.println(name);
}

As reference, an ArrayList has the following methods.

int size() Returns the number of elements in this list.
boolean add(Object value) Appends value onto list's end, returning true.
void get(int index) Returns value at index within list.
Object set(int index, Object value) Changes value at index to value, returning previous value there.
Object remove(int index) Removes value at index, shifting elements above beyond it forward one place over it.
void add(int index, Object value) Adds value at index, shifting elements there and beyond back one place to make room.

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