Java vs' C

1
Java vs. C

• By Abrar Siddiqui

2
What is C ?

• What do you guys think?
• C a new programming language or a new version of
  C/C ?
• It is a strong language for network and internet
  programming. C has redefined the programming
  landscape. In addition, C designed with the need
  of C/C and Java programmers. This new language
  has been developed specifically with the .NET
  framework in mind, and as such is designated to
  be the .NET developer's language of choice. One
  very important matter about C, it is the first
  component oriented programming language.

3
Differences with JAVA!

• Subtle Differences in terms of syntax of Java and
  C
• Slight modification of concepts in C that
  already exist in Java
• Language features and concepts that do not exist
  in Java at all.

4
Differences in terms of SyntaxJava main ? C
Main

• Java
• public static void main(String args)

• C
• static void Main(string args)
• string is shorthand for the System.String class
  in C. Another interesting point is that in C,
  your Main method can actually be declared to be
  parameter-less
• static void Main()

5
Differences in terms of SyntaxPrint statements

• Java
• System.out.println("Hello world!")

• C
• System.Console.WriteLine("Hello world!")
• or
• Console.WriteLine("Hello again!")

6
Differences in terms of SyntaxDeclaring
Constants

• Java
• In Java, compile-time constant values are
  declared inside a class as
• static final int K 100

• C
• To declare constants in C the const keyword is
  used for compile time constants while the
  readonly keyword is used for runtime constants.
  The semantics of constant primitives and object
  references in C is the same as in Java.
• const int K 100

7
Differences in terms of SyntaxInheritance

• C uses C syntax for inheritance, both for
  class inheritance and interface implementation as
  opposed to the extends and implements keywords.
• Java
• class B extends A implements Comparable

• C
• class BA, IComparable

8
Differences in terms of SyntaxPrimitive Types

• In Java, all integer primitive types (byte,
  short, int, long) are signed by default.
• In C there are both signed and unsigned
  varieties of these types
• Unsigned Signed Size
• byte sbyte 8 bits
• ushort short 16 bits
• uint int 32 bits
• ulong long 64 bits
• The only significantly different primitive in C
  is the decimal type, a type which stores decimal
  numbers without rounding errors. Eg
• decimal dec 100.44m

9
Differences in terms of SyntaxArray Declaration

• Java has two ways in which one can declare an
  array
• int iArray new int100 //valid
• float fArray new float100 //valid

• C uses only the latter array declaration syntax
• int iArray new int100 //valid
• float fArray new float100 //ERROR Won't
  compile

10
Modified concepts from JavaPolymorphism
Overriding

• The means of implementing polymorphism typically
  involves having methods in a base class that may
  be overridden by derived classes. These methods
  can be invoked even though the client has a
  reference to a base class type which points to an
  object of the derived class. Such methods are
  bound at runtime instead of being bound during
  compilation and are typically called virtual
  methods.
• In Java all methods are virtual methods while in
  C, as in C, one must explicitly state which
  methods one wants to be virtual since by default
  they are not.
• To mark a method as virtual in C, one uses the
  virtual keyword. Also, implementers of a child
  class can decide to either explicitly override
  the virtual method by using the override keyword
  or explicitly choose not to by using the new
  keyword instead

11
Modified concepts from JavaPolymorphism
Overriding

• Example
• using System
• public class Parent
• public virtual void DoStuff(string str)
• Console.WriteLine("In Parent.DoStuff "
  str)
• public class Child Parent
• public void DoStuff(int n)
• Console.WriteLine("In Child.DoStuff " n)
• public override void DoStuff(string str)
• Console.WriteLine("In Child.DoStuff "
  str)

public new void DoStuff(string str)
12
Modified concepts from JavaOperator Overloading

• Operator overloading allows standard operators in
  a language to be given new semantics when applied
  in the context of a particular class or type.
• Operator overloading can be used to simplify the
  syntax of certain operations especially when they
  are performed very often, such as string
  concatenation in Java or interactions with
  iterators and collections in the C Standard
  Template Library.
• Unlike C, C does not allow the overloading of
  the following operators new,( ), , , , or
  any variations of compound assignments such as
  , -, etc.

13
Modified concepts from JavaSwitch Statements

• There are two major differences between the
  switch statement in C versus that in Java.
• In C, switch statements support the use of
  string literals and do not allow fall-through
  unless the label contains no statements.
• switch(foo)
• case "A" Console.WriteLine("A seen")
• break
• case "B"
• case "C" Console.WriteLine("B or C seen")
• break
• / ERROR Won't compile due to fall-through at
  case "D" /
• case "D" Console.WriteLine("D seen")
• case "E" Console.WriteLine("E seen")
• break

14
Modified concepts from JavaMultiple Classes in
a Single File

• Multiple classes can be defined in a single file
  in both languages with some significant
  differences.
• In Java, there can only be one class per source
  file that has public access and it must have the
  same name as the source file.
• C does not have a restriction on the number of
  public classes that can exist in a source file
  and neither is there a requirement for the name
  of any of the classes in the file to match that
  of the source file.

15
Modified concepts from JavaImporting Libraries

• Both the langugaes support this functionality and
  C follows Javas technique for importing
  libraries
• C using keyword
• using System
• using System.IO
• using System.Reflection

• Java import keyword
• import java.util.
• import java.io.

16
New Concepts in CEnumerations

• Java's lack of enumerated types leads to the use
  of integers in situations that do not guarantee
  type safety.
• C code
• public enum Direction North1, East2, West4,
  South8
• Usage
• Direction wall Direction.North
• Java equivalent code will be
• public class Direction
• public final static int NORTH 1
• public final static int EAST 2
• public final static int WEST 3
• public final static int SOUTH 4
• Usage
• int wall Direction.NORTH

17
New Concepts in CEnumerations

• Despite the fact the Java version seems to
  express more, it doesn't, and is less type-safe,
  by allowing you to accidentally assign wall to
  any int value without the compiler complaining.
• C enumerations support the ToString method, so
  they can report their value as string (such as
  North") and not just an an integer.
• There also exists a static Parse method within
  the Enum class for converting a string to an
  enumeration.

18
New Concepts in Cforeach Statement

• The foreach loop is an iteration construct that
  is popular in a number of scripting languages
  (e.g. Perl, PHP, Tcl/Tk)
• The foreach loop is a less verbose way to iterate
  through arrays or classes that implement the the
  System.Collections.IEnumerable interface.
• Example
• string greek_alphabet "alpha", "beta",
  "gamma", "delta"
• foreach(string str in greek_alphabet)
• Console.WriteLine(str " is a greek letter")

19
New Concepts in CProperties

• Properties are a way to abstract away from
  directly accessing the members of a class,
  similar to how accessors (getters) and modifiers
  (setters) are used in Java.
• Particularly for read/write properties, C
  provides a cleaner way of handling this concept.
  The relationship between a get and set method is
  inherent in C, while has to be maintained in
  Java.
• It is possible to create, read-only, write-only
  or read-write properties depending on if the
  getter and setter are implemented or not.

20
New Concepts in CProperties

• Java
• public int getSize()
• return size
• public void setSize (int val)
• size val

• C
• public int Size
• get return size
• set size val

21
New Concepts in CPointers

• Although core C is like Java in that there is no
  access to a pointer type that is analogous to
  pointer types in C and C, it is possible to
  have pointer types if the C code is executing in
  an unsafe context.
• Pointer arithmetic can be performed in C within
  methods marked with the unsafe keyword.
• Example
• public static unsafe void Swap(int a, intb)
• int temp a
• a b
• b temp

22
New Concepts in CPass by Refernce

• In Java the arguments to a method are passed by
  value meaning that a method operates on copies of
  the items passed to it instead of on the actual
  items.
• In C, it is possible to specify that the
  arguments to a method actually be references.
• In Java trying to return multiple values from a
  method is not supported.
• The C keywords used are ref and out.
• ChangeMe(out s)
• Swap(ref a, ref b)

23
REFERENCES

• OOP with Microsoft VB.NET and Microsoft Visual
  C.NET
• by Robin A. Reyonlds-Haerle
• JAVA 2 Essentials
• by Cay Horstmann
• Websites
• Java vs. C Code to Code Comparison
• http//www.javacamp.org/javavscsharp/
• A Comparative Overview of C
• http//genamics.com/developer/csharp_comparative.
  htm
• C A language alternative or just J--?,
• http//www.javaworld.com/javaworld/jw-11-2000/jw-
  1122-csharp1.html
• A COMPARISON OF C TO JAVA By Dare Obasanjo
• http//www.soften.ktu.lt/mockus/gmcsharp/csharp/
  c-sharp-vs-java.htmlforeach
• Conversational C for Java Programmers by Raffi
  Krikorian
• http//www.ondotnet.com/pub/a/dotnet/2001/05/31/c
  sharp_4_java.html