Java Collections Framework: Methods & Algorithms

The List interface extends the Collections framework as well as the Iterable interface.

Java Collections Framework - List Interface

The List interface has over 2 dozen native methods as well as the methods it inherits from the Collection and Iterable interfaces.

Working with Lists

To show how to work with the List interface, we will start by creating an ArrayList and adding values to the first four positions (0, 1, 2, and 3) using the add() method:

List<String> myList = new ArrayList<>();
myList.add('This');
myList.add('makes');
myList.add('no');
myList.add('sense');

We can retrieve a single element from the ArrayList by using the get() method.

System.out.println(myList.get(1));

Next, we will replace one of the values and then iterate through the ArrayList to print it to the console.

myList.set(2, 'perfect');
for (String theValue : myList) {
System.out.print(theValue + ' ');
}

Executing this code results in the following output: This make perfect sense

Searching and Sorting Lists

Searching and sorting are common operations for Lists. To demonstrate, let's create an ArrayList to hold names:

List<String> listOfNames = new ArrayList<>();
listOfNames.add('jimmy');
listOfNames.add('sally');
listOfNames.add('cindy');
listOfNames.add('rhona');
listOfNames.add('john');
listOfNames.add('brenda');
listOfNames.add('lona');

Our list consists of 7 names. We will perform three operations on this list: search, sort, and change the names so their first letter is capitalized. One step at a time, let's search our list to see if we can find Brenda:

if (listOfNames.contains('brenda')) {
System.out.println('Record found!');
}
else {
System.out.println('Record not found!');
}

Collections.sort(listOfNames);
for (String theName : listOfNames) {
System.out.println(theName);
}

for (int i=0; i < listOfNames.size(); i++) {
String tempName = listOfNames.get(i);
listOfNames.set(i, tempName.substring(0, 1).toUpperCase() + tempName.substring(1));
}
for (String theName : listOfNames) {
System.out.println(theName);
}

System.out.println(listOfNames);