We create a Set as:
Set myset = new HashSet()
How do we create a List in Java?
How to make a new List in Java
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List myList = new ArrayList();
or with generics (Java 7 or later)
List<MyType> myList = new ArrayList<>();
or with generics (Old java versions)
List<MyType> myList = new ArrayList<MyType>();
Additionally, if you want to create a list that has things in it (though it will be fixed size):
List<String> messages = Arrays.asList("Hello", "World!", "How", "Are", "You");
In Java 8
To create a non-empty list of fixed size (operations like add, remove, etc., are not supported):
List<Integer> list = Arrays.asList(1, 2); // but, list.set(...) is supported
To create a non-empty mutable list:
List<Integer> list = new ArrayList<>(Arrays.asList(3, 4));
In Java 9
Using a new List.of(...) static factory methods:
List<Integer> immutableList = List.of(1, 2);
List<Integer> mutableList = new ArrayList<>(List.of(3, 4));
In Java 10
Using the Local Variable Type Inference:
var list1 = List.of(1, 2);
var list2 = new ArrayList<>(List.of(3, 4));
var list3 = new ArrayList<String>();
And follow best practices...
Don't use raw types
Since Java 5, generics have been a part of the language - you should use them:
List<String> list = new ArrayList<>(); // Good, List of String
List list = new ArrayList(); // Bad, don't do that!
Program to interfaces
For example, program to the List interface:
List<Double> list = new ArrayList<>();
Instead of:
ArrayList<Double> list = new ArrayList<>(); // This is a bad idea!
First read this, then read this and this. 9 times out of 10 you'll use one of those two implementations.
In fact, just read Sun's Guide to the Collections framework.
//simple example creating a list form a string array
String[] myStrings = new String[] {"Elem1","Elem2","Elem3","Elem4","Elem5"};
List mylist = Arrays.asList(myStrings );
//getting an iterator object to browse list items
Iterator itr= mylist.iterator();
System.out.println("Displaying List Elements,");
while(itr.hasNext())
System.out.println(itr.next());
List is just an interface just as Set.
Like HashSet is an implementation of a Set which has certain properties in regards to add / lookup / remove performance, ArrayList is the bare implementation of a List.
If you have a look at the documentation for the respective interfaces you will find "All Known Implementing Classes" and you can decide which one is more suitable for your needs.
Chances are that it's ArrayList.
List list = new ArrayList();
Or with generics
List<String> list = new ArrayList<String>();
You can, of course, replace string with any type of variable, such as Integer, also.
As declaration of array list in java is like
public class ArrayList<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, Serializable
There is numerous way you can create and initialize array list in java.
1) List list = new ArrayList();
2) List<type> myList = new ArrayList<>();
3) List<type> myList = new ArrayList<type>();
4) Using Utility class
List<Integer> list = Arrays.asList(8, 4);
Collections.unmodifiableList(Arrays.asList("a", "b", "c"));
5) Using static factory method
List<Integer> immutableList = List.of(1, 2);
6) Creation and initializing at a time
List<String> fixedSizeList = Arrays.asList(new String[] {"Male", "Female"});
Again you can create different types of list. All has their own characteristics
List a = new ArrayList();
List b = new LinkedList();
List c = new Vector();
List d = new Stack();
List e = new CopyOnWriteArrayList();
One example:
List somelist = new ArrayList();
You can look at the javadoc for List and find all known implementing classes of the List interface that are included with the java api.
Sometimes - but only very rarely - instead of a new ArrayList, you may want a new LinkedList. Start out with ArrayList and if you have performance problems and evidence that the list is the problem, and a lot of adding and deleting to that list - then - not before - switch to a LinkedList and see if things improve. But in the main, stick with ArrayList and all will be fine.
Using Google Collections, you could use the following methods in the Lists class
import com.google.common.collect.Lists;
// ...
List<String> strings = Lists.newArrayList();
List<Integer> integers = Lists.newLinkedList();
There are overloads for varargs initialization and initialising from an Iterable<T>.
The advantage of these methods is that you don't need to specify the generic parameter explicitly as you would with the constructor - the compiler will infer it from the type of the variable.
There are many ways to create a Set and a List. HashSet and ArrayList are just two examples. It is also fairly common to use generics with collections these days. I suggest you have a look at what they are
This is a good introduction for java's builtin collections. http://java.sun.com/javase/6/docs/technotes/guides/collections/overview.html
List can be created in many ways:
1 - Constructor Initialization
List is an interface, and the instances of List can be created in the following ways:
List<Integer> list=new ArrayList<Integer>();
List<Integer> llist=new LinkedList<Integer>();
List<Integer> stack=new Stack<Integer>();
2- Using Arrays.asList()
List<Integer> list=Arrays.asList(1, 2, 3);
3- Using Collections class methods
Empty List
List<Integer> list = Collections.EMPTY_LIST;
OR
List<Integer> list = Collections.emptyList();
Collections.addAll(list = new ArrayList<Integer>(), 1, 2, 3, 4);
Unmodifiable List
List<Integer> list = Collections
.unmodifiableList(Arrays.asList(1, 2, 3));
Singleton List
List<Integer> list = Collections.singletonList(2);
You can find more way from the reference link below.
Reference:
Try this:
List<String> messages = Arrays.asList("bla1", "bla2", "bla3");
Or:
List<String> list1 = Lists.mutable.empty(); // Empty
List<String> list2 = Lists.mutable.of("One", "Two", "Three");
If you need a serializable, immutable list with a single entity you can use:
List<String> singList = Collections.singletonList("stackoverlow");
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