ArrayLists - Building Java Programs: A Back to Basics Approach - page 631

Table 10.1 Basic ArrayList Methods

Method Description

ArrayList<String> example

add(value ) adds the given value at the end of

list.add("end");

the list

adds the given value at the given index,

add(index, value) list.add(1, "middle");

shifting subsequent values right

removes all elements from the list

clear() list.clear();

gets the value at the given index get(index) list.get(1)

removes the value at the given

remove(index) list.remove(1);

index, shifting subsequent values left

replaces the value at the given

set(index, value) list.set(2, "hello");

index with the given value

returns the current number of elements

size() list.size()

in the list

You can construct an ArrayList<String> to hold these names and use the
contains method to ensure that there are no duplicates:

// removes duplicates from a list
Scanner input = new Scanner(new File("names.txt"));
ArrayList<String> list = new ArrayList<String>();
while (input.hasNext()) {
String name = input.next();
if (!list.contains(name)) {
list.add(name);

}

}
System.out.println("list = " + list);

Given the sample input file, this code produces the following output:

list = [Maria, Derek, Erica, Livia, Jack, Anita, Kendall, Jamie]

Notice that only 8 of the original 13 names appear in this list, because the various
duplicates have been eliminated.
Sometimes it is not enough to know that a value appears in the list. You may want
to know exactly where it occurs. For example, suppose you want to write a method to
replace the first occurrence of one word in an ArrayList<String> with another
word. You can call the set method to replace the value, but you have to know where
it appears in the list. You can find out the location of a value in the list by calling the
indexOf method.