Comparison and conversion between Java and C # syntax

Java (J2SE 5.0) and C # Comparison
This is a quick reference guide to highlight some key syntactical differences Java and C #.
This is by no means a complete overview of either language. Hope you find this useful!
Also the vb.net and C # Comparison.

Comments Data Types Constants Enumerations Operators

Choices Loops Arrays Functions Strings

Exception Handling Namespaces Classes/interfaces Constructors/destructors Objects

Properties Structs Console I/O File I/O

Java Comments C#
Single /* Multiple Line * * /** Javadoc Documentation Comments * *	Single /* Multiple Line * * XML comments on a single /** XML comments on multiple lines * *
Java Data Types C#
Primitive Types Boolean byte char short, int, long float, double Reference Types object   (superclass of all other classes) String Arrays, classes, interfaces Conversions //int to String int x = 123; String y = integer.tostring (x); //Y is "123" //String to int y = "456";   x = Integer.parseint (y);  //X are 456 // double to Intdouble z = 3.5; x = (int) z;  //x is 3  (truncates decimal)	Value Types bool BYTE, sbyte Char Short, ushort, int, uint, long, ulong float, double, decimal Structures, enumerations Reference Types Object (superclass of all other classes) String arrays, classes, interfaces, delegates Convertions int to String int x = 123; String y = x.tostring (); Y is "123" string to int y = "456"; x = Int.   Parse (y); or x = Convert.ToInt32 (y); Double to int Double z = 3.5; x = (int) z; X is 3 (truncates decimal)
Java Constants C#
May is initialized in a constructor final Double PI = 3.14;	Const Double PI = 3.14; Can is set to a const or a variable. May is initialized in a constructor. readonly int max_height = 9;
Java Enumerations C#
enum Action {Start, Stop, Rewind, Forward}; //Special type of Class enum Status {   flunk (m), pass (in), Excel (in);   private final int value;   Status (int value) {this.value = value;}   public int value () {return value;} }; Action a = action.stop; if (a!= action.start)   System.out.println (a);               //Prints "Stop" Status s = status.pass; System.out.println (S.value ());      //Prints	enum Action {Start, Stop, Rewind, Forward}; enum Status {flunk = +, pass = N, Excel = 90}; No equivalent. Action a = Action.stop; if (a!= action.start) Console.WriteLine (a); Prints "Stop" Status s = status.pass; Console.WriteLine ((int) s); Prints "70"
Java Operators C#
Comparison ==  <  >  <=  >= != Arithmetic + -  *& nbsp / %  (MoD) /   (integer division If both operands are ints) Math.pow (x, y) Assignment =  +=  =  *= /=  %=   &=  |=  ^=  <<=  >>=  > >>=  ++ -- Bitwise &  |  ^   ~  <<  >>& nbsp >>> Logical &&  | |   &  |   ^  ! Note: && and | |  perform short-circuit logical evaluations String concatenation +	Comparison = = < > <= >=!= Arithmetic +  -  *  / % (MoD) /(integer division If both operands are ints) Math.pow (x, y) Assignment = + = = *=/=%= &= |= ^= <<= >>= + +-- Bitwise & | ^ ~ << >> Logical && | |   & | ^   ! Note: && | | Perform short-circuit logical evaluations String concatenation +
Java Choices C#
Greeting = Age < ? "What ' s up?" : "Hello"; if (x < y) System.out.println ("greater"); if (x!= 100) { x *= 5; Y *= 2; } Else Z *= 6; int selection = 2; Switch (selection) {//Must be-byte, short, int, char, or enum case 1:x++; Falls through to next if no break case 2:y++; Break ; case 3:z++; Break ; default: other++; }	Greeting = Age < ? "What ' s up?" : "Hello"; If (x < y)     Console.WriteLine ("Greater"); If (x!=) {      x *= 5;   y *= 2; } else   Z *= 6; String color = "Red"; Switch (color)  {                          /Can is any predefined type   Case "Red":    r++;    break;       //break is mandatory; No Fall-through   case "Blue":   b++;   break;   Case "green": g++;   break;   Default:  other++;      break;       //Break necessary on default }
Java Loops C#
while (I < 10) i++; for (i = 2; I <= i + + 2) System.out.println (i); Todo i++; while (I < 10); for (int i : numarray)//foreach Construct sum + = i; For loop can is used to iterate through any Collection Import java.util.ArrayList; arraylist<object> list = new arraylist<object> (); List.add (10); Boxing converts to instance of Integer List.add ("Bisons"); List.add (2.3); Boxing converts to instance of Double for (Object o : list) System.out.println (o);	while (I < 10) i++; for (i = 2; I <= i + + 2) Console.WriteLine (i); Todo i++; while (I < 10); foreach (int i in Numarray) sum + = i; foreach can be used to iterate through any collection Using System.Collections; ArrayList list = new ArrayList (); List. ADD (10); List. ADD ("Bisons"); List. ADD (2.3); foreach (Object o in list) Console.WriteLine (o);
Java Arrays C#
int nums [] = {1, 2, 3};   or   int [] nums = {1, 2, 3 }; for (int i = 0; i < nums.length i++)   System.out.println (nums[i]); String names[] = new STRING[5]; Names[0] = "David"; Float Twod [[] = new Float[rows][cols]; TWOD[2][0] = 4.5; int [[] jagged = new int[5][]; Jagged[0] = new INT[5]; Jagged[1] = new INT[2]; Jagged[2] = new INT[3]; Jagged[0][4] = 5;	int [] nums = {1, 2, 3}; for (int i = 0; i < Nums. Length; i++)   Console.WriteLine (Nums[i]); string[] names = new String[5]; Names[0] = "David"; Float [,] Twod = new float[rows, cols]; twod[2,0] = 4.5f; int [[] jagged = new int[3][] {     new int[5], new int[2], new int[3]}; Jagged[0][4] = 5;
Java Functions C#
Return single value int ADD (int x, int y) { return x + y; } int sum = ADD (2, 3); Return no value void Printsum (int x, int y) { System.out.println (x + y); } Printsum (2, 3); Primitive types and references are always passed by value void TestFunc (int x, point p) { x + +; p.x++; Modifying property of the object p = null; Remove Local reference to Object } Class Point { public int x, y; } Point P = new Point (); p.x = 2; int a = 1; TestFunc (A, p); System.out.println (A + "" + p.x + "" + (P = null)); 1 3 False Accept variable number of arguments int Sum (int ... nums) { int sum = 0; for (int i:nums) sum + = i; return sum; } int total = Sum (4, 3, 2, 1); Returns 10	Return single value int ADD (int x, int y) { return x + y; } int sum = ADD (2, 3); Return no value void Printsum (int x, int y) { Console.WriteLine (x + y); } Printsum (2, 3); Pass through value (default), In/out-reference (ref), and out-reference (out) void TestFunc (int x, ref int y, out int Z, point p1, ref point p2) { x + +;  y++; z = 5; p1.x++; Modifying property of the object P1 = null; Remove Local reference to Object P2 = null; Free the object } Class Point { public int x, y; } Point P1 = new Point (); Point P2 = new Point (); p1.x = 2; int a = 1, b = 1, C; Output param doesn ' t need initializing TestFunc (A, ref B, out C, p1, ref p2); Console.WriteLine ("{0} {1} {2} {3} {4}"), A, B, C, p1.x, p2 = null); 1 2 5 3 True Accept variable number of arguments int Sum (params int[] nums) { int sum = 0; foreach (int i in nums) sum + = i; return sum; } int total = Sum (4, 3, 2, 1); Returns 10
Java Strings C#
String concatenation String School = "Harding"; School = school + "University"; School is "Harding University" String comparison String mascot = "Bisons"; if (mascot = = "Bisons")//not the correct way todo string comparisons if (mascot. equals("bisons"))//True if (mascot. Equalsignorecase("bisons"))//True if (mascot. CompareTo("bisons") = = 0)//True System.out.println (mascot.    Substring(2, 5)); Prints "Son" My Birthday:oct 12, 1973 Java.util.Calendar C = new Java.util.GregorianCalendar (1973, 10, 12); String s = String.Format ("My Birthday:%1$tb%1$te,%1$ty", c); mutable string stringbuffer buffer = new StringBuffer("two"); Buffer. Append ("three"); Buffer. Insert (0, "one"); Buffer. Replace (4, 7, "two"); SYSTEM.OUT.PRINTLN (buffer); Prints "One Two three"	String concatenation string school = "Harding"; School = school + "University"; School is "Harding University" String comparison String mascot = "Bisons"; if (mascot = = "Bisons")//True if (mascot. Equals("bisons"))//True if (mascot. ToUpper(). Equals   ("Bisons")) True if (mascot. CompareTo("bisons") = = 0)//True Console.WriteLine (mascot.     Substring(2, 3)); Prints "Son" My Birthday:oct 12, 1973 DateTime dt = new DateTime (1973, 10, 12); string s = "My Birthday:" + dt. ToString ("MMM dd, yyyy"); mutable string System.Text. StringBuilder buffer = new System.Text. StringBuilder ("two"); Buffer. Append ("three"); Buffer. Insert (0, "one"); Buffer. Replace ("Two", "two"); Console.WriteLine (buffer); Prints "One Two three"
Java Exception Handling C#
//Must be in a method that are declared to throw this exception Exception ex = new Exception ("Somet Hing is really wrong. "); throw ex;   Try {   y = 0;   x = 10/y; } Catch (Exception ex) {   System.out.println (Ex.getmessage ());   } Finally {  //Code that always gets executed }	Exception up = new Exception ("Some Thing is really wrong. "); throw up; /ha ha Try {   y = 0;   x = 10/y; } Catch (Exception ex) {     //Variable "Ex" is optional   Console.WriteLine (ex. message); } finally {  //Code that always gets executed }
Java Namespaces C#
package Harding.compsci.graphics; Import Harding.compsci.graphics.Rectangle; Import Single class import harding.compsci.graphics.*; Import All Classes	namespace Harding.Compsci.Graphics { ... } Or namespace Harding { namespace CompSci { namespace Graphics { ... } } } Import all class. Can ' t import single class. using Harding.Compsci.Graphics;