No, the final keyword does not make the list, or its contents immutable. If you want an immutable List, you should use: List<Synapse> unmodifiableList = Collections.unmodifiableList (synapses);
Full Answer
Can we declare a List as final?
No, the final keyword does not make the list, or its contents immutable. If you want an immutable List, you should use: List
What happens if we declare List as final?
So, when we declare an object variable as final, it means that the variable cannot be changed to refer to anything else.
Can we have ArrayList as final?
If We declare ArrayList as final we can still add elements to it but we can't reassign it.
How do you declare a final ArrayList in Java?
public final ArrayList anotherArrayList = new ArrayList(); anotherArrayList. addAll(someArrayList);
Can we declare list as null?
Yes, We can insert null values to a list easily using its add() method. In case of List implementation does not support null then it will throw NullPointerException.
Can we declare static as final?
Declaring variables only as static can lead to change in their values by one or more instances of a class in which it is declared. Declaring them as static final will help you to create a CONSTANT. Only one copy of variable exists which can't be reinitialize.
Is List immutable in Java?
ImmutableList, as suggested by the name, is a type of List which is immutable. It means that the content of the List are fixed or constant after declaration, that is, they are read-only. If any attempt made to add, delete and update elements in the List, UnsupportedOperationException is thrown.
Which is better List or ArrayList?
The List is an interface, and the ArrayList is a class of Java Collection framework. The List creates a static array, and the ArrayList creates a dynamic array for storing the objects. So the List can not be expanded once it is created but using the ArrayList, we can expand the array when needed.
How do you declare a final List in Java?
How do you declare a list of objects in Java?#1) Using The asList Method.#2) Using List. add()#3) Using Collections Class Methods.#4) Using Java8 Streams.#5) Java 9 List. of() Method.#1) Using For Loop/Enhanced For Loop.#2) Using The toString Method.
Can a List be static?
Static - A static list is a set of specific contacts that you add or upload yourself (or that contacts are added to when they fill out a sign-up form). Dynamic - Dynamic lists use segmentation to select and automatically update groups of contacts based on shared attributes.
Is ArrayList LIFO or FIFO?
ArrayList is random access. You can insert and remove elements anywhere within the list. Yes, you can use this as a FIFO data structure, but it does not strictly enforce this behavior. If you want strict FIFO, then use Queue instead.
Can List be static in Java?
public static String[] list; We define String list as String[] and object name. list = new String[] { "One", "Two", "Three", "Four", "Five" }; Using for loop we need to fetch the values of list and print them to screen.
What is the impact of declaring method as final?
You use the final keyword in a method declaration to indicate that the method cannot be overridden by subclasses.
What does it mean if a variable is declared final?
Once any entity (variable, method or class) is declared final , it can be assigned only once. That is, the final variable cannot be reinitialized with another value. the final method cannot be overridden.
What effect does Declaring a method as final have?
A method declared as final can't be overridden. A sub-class can't have the same method signature with a different implementation.
What happens if we declare a class as final in Java?
The final class is a class that is declared with the final keyword. We can restrict class inheritance by making use of the final class. final class means that the class cannot be extended or inherited. If we try to inherit a final class, then the compiler throws an error during compilation.
Can you add an element later in a list?
But why would you want to do that? You can always add the element later to the list (Declaring it as final means you cannot assign it to another List but you can always add content to it).
Can you replace elements with set?
But you can replace elements using set. (Reply to Wouter's question.)
Is Arrays.asList immutable?
Because you can call set () on the list returned by Arrays.asList (), it is not immutable.
Does Java have a literal syntax?
Java does not have a literal syntax for collections such as lists, maps etc. (this might be a feature that will be included in some future version of Java). Mike's answer is good if you really want an immutable list. I'd also make the member variable static; you do not need an instance of the list for each object that you create with the class. The usual convention for static final variables in Java is to have all-capital names:
What does it mean when you mark a list reference final?
However when you mark the list reference final it implies that the reference cant be pointed to any other list object other than this.
What is final in Java?
Final is a keyword or reserved word in java and can be applied to member variables, methods, class and local variables in Java. Once you make a reference final you are not allowed to change that reference and compiler will verify this and raise compilation error if you try to re-initialized final variables in java.
What method to use to make an immutable list?
If you really want an immutable list, you should use the Collections.unmodifiableList () method.
How to get an immutable list?
1. To get a really immutable list, you will have to make deep copies of the contents of the list. UnmodifiableList would only render the list of references somewhat immutable. Now making a deep copy of the List or array will be tough on memory with the growing size.
Why do I mark collections as final?
This works because, once the value is already assigned to a final variable, it can never be reassigned to another value, including null.
What does "can't re-assign reference" mean?
It just means that you can't re-assign its reference. Attempting to do something like the below will lead to compiler error.
What happens when you combine the final keyword with the use of Collections.unmodifiableList?
If you combine the final keyword with the use of Collections.unmodifiableList, you ge the behaviour you are probably trying to achieve, for instance:
What is the purpose of making a final method?
i.e. you cannot provide implementation to the superclass’s final method from the subclass. i.e. The purpose of making a method final is to prevent modification of a method from outside (child class).
Can you declare constructors as final?
The child class inherits all the members of the superclass except the constructors. In other words, constructors cannot be inherited in Java, therefore, you cannot override constructors. So, writing final before constructors make no sense.
Does Java allow final before constructor?
So, writing final before constructors make no sense. Therefore, java does not allow final keyword before a constructor. If you try, make a constructor final a compile-time error will be generated saying “modifier final not allowed here”.
What does it mean when an array is declared as final?
So, when we declare an object variable as final, it means that the variable cannot be changed to refer to anything else.
What does "final array" mean?
So a final array means that the array variable which is actually a reference to an object, cannot be changed to refer to anything else, but the members of array can be modified.
Why do we need to make it final in inheritance?
If we are using inheritance and we need some methods not to overridden in subclasses then we need to make it final so that those methods can't be overridden by subclasses.
Can you declare a main method as final in Java?
Yes, we can declare the main () method as final in Java. The compiler does not throw any error.
Can a final method be overridden?
The compiler does not throw any error. If we declare any method as final by placing the final keyword then that method becomes the final method. The main use of the final method in Java is they are not overridden. We can not override final methods in subclasses.
What does it mean when a variable is declared with the final keyword?
When a variable is declared with final keyword, its value can’t be modified, essentially, a constant. This also means that you must initialize a final variable. If the final variable is a reference, this means that the variable cannot be re-bound to reference another object, but the internal state of the object pointed by that reference variable can be changed i.e. you can add or remove elements from the final array or final collection. It is good practice to represent final variables in all uppercase, using underscore to separate words.
What is final in Java?
final keyword is used in different contexts. First of all, final is a non-access modifier applicable only to a variable, a method or a class. Following are different contexts where final is used.
What is the difference between const and final variables in C++?
Note the difference between C++ const variables and Java final variables. const variables in C++ must be assigned a value when declared. For final variables in Java, it is not necessary as we see in the above examples. A final variable can be assigned value later, but only once.
What is the difference between a final variable and a normal variable?
The only difference between a normal variable and a final variable is that we can re-assign the value to a normal variable but we cannot change the value of a final variable once assigned. Hence final variables must be used only for the values that we want to remain constant throughout the execution of the program.
What is a final method?
When a method is declared with final keyword, it is called a final method. A final method cannot be overridden. The Object class does this—a number of its methods are final. We must declare methods with the final keyword for which we are required to follow the same implementation throughout all the derived classes.
When to initialize a final variable?
You can initialize a final variable when it is declared. This approach is the most common. A final variable is called a blank final variable if it is not initialized while declaration. Below are the two ways to initialize a blank final variable.
Where is the final variable initialized?
A blank final variable can be initialized inside an instance-initializer block or inside the constructor. If you have more than one constructor in your class then it must be initialized in all of them, otherwise, a compile-time error will be thrown.
