Final variable manipulation in Java

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Could anyone please tell me what is the meaning of the following line in context of Java:

final variable can still be manipulated unless it's immutable

As far as I know, by declaring any variable as final, you can't change it again, then what they mean with the word immutable in above line?

It means that if your final variable is a reference type (i.e. not a primitive like int), then it's only the reference that cannot be changed. It cannot be made to refer to a different object, but the fields of the object it refers to can still be changed, if the class allows it. For example:

final StringBuffer s = new StringBuffer();

The content of the StringBuffer can still be changed arbitrarily:


But you cannot say:

s = null;


s = anotherBuffer;

On the other hand:

final String s = "";

Strings are immutable - there simply isn't any method that would enable you to change a String (unless you use Reflection - and go to hell).

Final variable manipulation in Java, final modifier is applicable for variable but not for objects, Whereas immutability applicable for an object but not for variables. By declaring a reference variable as � Final is a modifier in java, final can be applied to a variable, method or classes. Once the modifier was added to the class all variables & methods of that class would be immutable implicitly. Making class immutable provides several benefits such as It is read-only & can not be safely shared in the multiple threads without any synchronization.

If you have a final reference to a Java object you can still manipulate it but cannot change its reference. For instance this code is perfectly legal:

import javax.swing.JLabel;

class Test1 {
    private final static JLabel l = new JLabel("Old text");
    public static void main(String[] args) {
        l.setText("New Text");

But you can't say:

l = new JLabel("Newest Text");

After the first assignment to l. Note that you can do this though:

import javax.swing.JLabel;

class Test1 {
    public static void main(String[] args) {
        final JLabel l;
        String s = getArbitaryString(); // Assume this method returns a string
        l = new JLabel(s);

This can be done because when l is declared it is not assigned to anything not even null. So you are allowed to assign something to it one time only.

Same thing goes for primitives. You can assign a value to it like this:

class Test1 {
    public static void main(String[] args) {
        final int i;
        i = 2;

But now you cannot manipulate it further since the only thing you can do to primitive types is to assign values to them.

final vs Immutability in Java, A variable provides us with named storage that our programs can manipulate. There are two types of data variables in a class: Instance variables : Instance� Final Variables. If a variable is declared as final, the values can not be modified once it is assigned. This is very useful if you want to prevent the manipulation of values in the future flow of your application. If a final variable is not initialized at the time of declaration, it is called as blank final variable.

You cannot change what object or value a final variable refers to. You can only assign a final variable once.

This has no effect on whether you can change the state of the object. The object itself can still be manipulated unless it is coded in such a way that this manipulation is forbidden. An immutable object is an object whose state cannot change.

Static and non static blank final variables in Java, In Java, final is the access modifier which can be used with a filed, class and a method.When a method if final it cannot be overridden.When a� A variable is a memory area, and this memory location gets affected when any manipulation or operation is done on the variables. In Java, we should declare all the variables before using them. Each variable has a specific data type, which determines its memory and the type of data that it can store.

As others have said, it means that you can manipulate the object the variable points at, but you cannot change the reference (i.e. assign another object to the variable).

Objects that are mutable by design, such as a List can be changed (you can add elements to them) whereas if you have an immutable object such as a String or Integer you won't be able to change it (all the operations the class String supports return a new instance, and don't modify the actual object).

How many ways are there to initialize a final variable in java?, It is mostly used with static to create a constant class variable. For Example: final int a =0;. We can also declare reference variables final also, in this case, one� The method call will throw an IllegalAccessException if it fails to match the access mode required by the method with the one allowed by the variable. For example, this will happen if we try to use a set() method on a final variable. 6. Memory Ordering Effects

The one that always kills me?

If you want final variables to actually be as safe as you thought they were, you need a lot of extra code to return a copy of a String[].

Final Keyword in Java, hi if you use "final" keyword, then you just make the reference final, that is you will not be able to re-assign the reference. if your final reference� The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available. See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.

Manipulating final variable (Java in General forum at Coderanch), Java has a set of basic variable manipulation operations. an integer type, all fractions in the result of the division will be cut off the final result. Q #37) What is the final keyword in Java? Answer: Final variable: Once a variable is declared as final, then the value of the variable could not be changed. It is like a constant. Example: final int = 12; Final method: A final keyword in a method, couldn’t be overridden. If a method is marked as a final, then it can’t be overridden by the

Java Operations, Final variables. If a variable is declared with the final keyword, its value cannot be changed once initialized. Note that the variable does not necessarily have� The use of final keyword is just like that occurs in Java In java final has three uses 1) prevent class Inheritance 2) prevent method overriding or redifination of method in subclass 3) and to declare constants But the third point seems to be missing from the PHP I guess, as i am a java developer Currently gaining competence in PHP

What is the final keyword in Java?, Could anyone please tell me what is the meaning of the following line in context of Java: final variable can still be manipulated unless it's� String manipulation is very important to know in any programming language and it is used on a daily basis by developers. Recommended Articles: This has been a guide to String functions in Java. Here we have discussed the different methods of string functions in java with examples. You may also look at the following article to learn more –

  • @pramodc84: It's the same for all variables. Most collections are mutable though.
  • So how can I change it with reflection? =)
  • @Daniel Magnusson: use… to make the private char[] inside String accessible.
  • +1 unless you use Reflection - and go to hell - just love a good humor coming from a bad experience :)))
  • @Viraj: In Java, only variables can be final, not objects. So in your code, final only applies to the reference newTask. But the array object which it refers to can sill have its elements changed.
  • You can but that's not what he meant.
  • Actually, you can't. You would get a java.lang.IllegalAccessException.
  • No you can't. You get java.lang.IllegalAccessException: Can not set final [type] field [fieldname] to [type of new value].
  • It's documented here too:… -- "IllegalAccessException when Modifying Final Fields"
  • @polygenelubricants -… says this: "If the underlying field is final, the method throws an IllegalAccessException unless setAccessible(true) has succeeded for this field and this field is non-static."