INHERITANCE AND POLYMORPHISM - Introduction to Java Programming - page 433

List size? 6
Is Miami in the list? True
The location of Denver in the list? 1
Is the list empty? false
[London, Xian, Paris, Seoul, Tokyo]
Tokyo Seoul Paris Xian London
The area of the circle? 12.566370614359172

Since the ArrayList is in the java.util package, it is imported in line 1. The program
creates an ArrayList of strings using its no-arg constructor and assigns the reference to
cityList (line 6). The add method (lines 9-19) adds strings to the end of list. So, after
cityList.add("London") (line 9), the list contains

add(Object)

[London]

After cityList.add("Denver") (line 11), the list contains

[London, Denver]

After adding Paris , Miami , Seoul , and Tokyo (lines 13-19), the list contains

[London, Denver, Paris, Miami, Seoul, Tokyo]

Invoking size() (line 22) returns the size of the list, which is currently 6 . Invoking
contains("Miami") (line 24) checks whether the object is in the list. In this case, it returns
true , since Miami is in the list. Invoking indexOf("Denver") (line 26) returns the index of
Denver in the list, which is 1 . If Denver were not in the list, it would return -1 . The isEmpty()
method (line 28) checks whether the list is empty. It returns false , since the list is not empty.
The statement cityList.add(2, "Xian") (line 31) inserts an object into the list at the
specified index. After this statement, the list becomes

size()

add(index, Object)

[London, Denver, Xian, Paris, Miami, Seoul, Tokyo]

The statement cityList.remove("Miami") (line 35) removes the object from the list.
After this statement, the list becomes

remove(Object)

[London, Denver, Xian, Paris, Seoul, Tokyo]

The statement cityList.remove(1) (line 39) removes the object at the specified index
from the list. After this statement, the list becomes

remove(index)

[London, Xian, Paris, Seoul, Tokyo]

The statement in line 43 is same as

System.out.println(cityList);

The toString() method returns a string representation of the list in the form of
[e0.toString(), e1.toString(), ..., ek.toString()] , where e0 , e1 , . . . , and
ek are the elements in the list.
The get(index) method (line 47) returns the object at the specified index.
ArrayList objects can be used like arrays, but there are many differences. Table 11.1 lists
their similarities and differences.
Once an array is created, its size is fixed. You can access an array element using the
square-bracket notation (e.g., a[index] ). When an ArrayList is created, its size is 0 .

toString()

getIndex()
array vs. ArrayList