What is the equivalent of Java s final in C

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sealed

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http   en csharp-online net CSharp FAQ  What are the differences between CSharp and Java constant declarations  C  constants are declared using the const keyword for compile time constants or the readonly keyword for runtime constants  The semantics of constants is the same in both the C  and Java languages

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Java class final and method final -  sealed  Java member variable final -  readonly for runtime constant  const for compile time constant   No equivalent for Local Variable final and method argument final

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What everyone here is missing is Java s guarantee of definite assignment for final member variables   For a class C with final member variable V  every possible execution path through every constructor of C must assign V exactly once - failing to assign V or assigning V two or more times will result in an error   C  s readonly keyword has no such guarantee - the compiler is more than happy to leave readonly members unassigned or allow you to assign them multiple times within a constructor   So  final and readonly  at least with respect to member variables  are definitely not equivalent - final is much more strict

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As mentioned  sealed is an equivalent of final for methods and classes  As for the rest  it is complicated   For static final fields  static readonly is the closest thing possible  It allows you to initialize the static field in a static constructor  which is fairly similar to static initializer in Java  This applies both to constants  primitives and immutable objects  and constant references to mutable objects  The const modifier is fairly similar for constants  but you can t set them in a static constructor   On a field that shouldn t be reassigned once it leaves the constructor  readonly can be used  It is not equal though - final requires exactly one assignment even in constructor or initializer   There is no C  equivalent for a final local variable that I know of  If you are wondering why would anyone need it  You can declare a variable prior to an if-else  switch-case or so  By declaring it final  you enforce that it is assigned at most once  Java local variables in general are required to be assigned at least once before they are read  Unless the branch jumps out before value read  a final variable is assigned exactly once  All of this is checked compile-time  This requires well behaved code with less margin for an error    Summed up  C  has no direct equivalent of final  While Java lacks some nice features of C   it is refreshing for me as mostly a Java programmer to see where C  fails to deliver an equivalent

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The final keyword has several usages in Java  It corresponds to both the sealed and readonly keywords in C   depending on the context in which it is used  Classes To prevent subclassing  inheritance from the defined class   Java public final class MyFinalClass        C  public sealed class MyFinalClass        Methods Prevent overriding of a virtual method  Java public class MyClass       public final void myFinalMethod            C  public class MyClass   MyBaseClass       public sealed override void MyFinalMethod            As Joachim Sauer points out  a notable difference between the two languages here is that Java by default marks all non-static methods as virtual  whereas C  marks them as sealed  Hence  you only need to use the sealed keyword in C  if you want to stop further overriding of a method that has been explicitly marked virtual in the base class  Variables To only allow a variable to be assigned once  Java public final double pi   3 14     essentially a constant  C  public readonly double pi   3 14     essentially a constant  As a side note  the effect of the readonly keyword differs from that of the const keyword in that the readonly expression is evaluated at runtime rather than compile-time  hence allowing arbitrary expressions

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It depends on the context    For a final class or method  the C  equivalent is sealed  For a final field  the C  equivalent is readonly  For a final local variable or method parameter  there s no direct C  equivalent

[c#] What is the equivalent of Java's final in C#?

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