INHERITANCE AND POLYMORPHISM - Introduction to Java Programming: Comprehensive Version - page 438

11.32

Suppose the ArrayList list contains {"Dallas", "Dallas", "Houston",
"Dallas"} . What is the list after invoking list.remove("Dallas") one time?
Does the following code correctly remove all elements with value "Dallas" from
the list? If not, correct the code.

for ( int i = 0 ; i < list.size(); i++)
list.remove( "Dallas" );

11.33

Explain why the following code displays [1, 3] rather than [2, 3] .

ArrayList<Integer> list = new ArrayList<>();
list.add( 1 );
list.add( 2 );
list.add( 3 );
list.remove( 1 );
System.out.println(list);

11.34

Explain why the following code is wrong.

ArrayList<Double> list = new ArrayList<>();
list.add( 1 );

11.12 Useful Methods for Lists
Java provides the methods for creating a list from an array, for sorting a list, and
finding maximum and minimum element in a list, and for shuffling a list.

Key
Point

Often you need to create an array list from an array of objects or vice versa. You can write the
code using a loop to accomplish this, but an easy way is to use the methods in the Java API.
Here is an example to create an array list from an array:

array to array list

String[] array = { "red" , "green", "blue" };
ArrayList<String> list = new ArrayList<>(Arrays.asList(array));

The static method asList in the Arrays class returns a list that is passed to the ArrayList
constructor for creating an ArrayList . Conversely, you can use the following code to create
an array of objects from an array list.

array list to array

String[] array1 = new String[list.size()];
list.toArray(array1);

Invoking list.toArray(array1) copies the contents from list to array1 .
If the elements in a list are comparable such as integers, double, or strings, you can use the
static sort method in the java.util.Collections class to sort the elements. Here are
examples:

sort a list

Integer[] array = { 3 , 5 , 95 , 4 , 15 , 34 , 3 , 6 , 5 };
ArrayList<Integer> list = new ArrayList<>(Arrays.asList(array));
java.util.Collections.sort(list);
System.out.println(list);

You can use the static max and min in the java.util.Collections class to return the
maximum and minimal element in a list. Here are examples:

max and min methods

Integer[] array = { 3 , 5 , 95 , 4 , 15 , 34 , 3 , 6 , 5 };
ArrayList<Integer> list = new ArrayList<>(Arrays.asList(array));
System.out.println(java.util.Collections.max(list));
System.out.println(java.util.Collections.min(list));