C++, Java, and C#

Java vs. C++

Java was designed after C++. If you come from a C++ background, it may help to note that, in Java:

• There are no global variables nor global functions
• boolean is NOT considered an integral type (you can't even cast between integers and booleans)
• There's no preprocessor, so no #define, #include, #ifdef, ...
• There no need for "header files" — the class file contains everything a client needs to use the class.
• You cannot write "long int" — you must say "long"
• Uses Unicode, not ASCII, is used
• There are explicit pointers
• Arrays know their size
• There's a much nicer syntax for arrays and array types
• There are operators: instanceof, ">>>", ">>>="
• There are no operators: sizeof, &, "*", "->", ".*", ".->"
• Break and continue statements may be labeled
• There's no goto statement
• Forward references are fine and used all the time
• There's no separation of class declaration and definition (use interfaces instead)
• There're no structs, unions, bitfields, typedefs (structs can be simulated; the others aren't needed)
• There's no special syntax for base class or member construction
• Class fields are automatically initialized to default values
• You can supply initial values of fields at point of field declaration
• Garbage collection of objects is implied
• Classes can be final (meaning you can NOT extend them)
• Synchronization is built into the language
• You don't mark methods "virtual" to get overriding
• There's no multiple inheritance (use interfaces anyway)
• "Templates" are much simpler than those of C++
• There's no operator overloading
• Single argument constructors are automatically "explicit"
• Any object can be a monitor
• String objects are NOT arrays of characters: you cannot use the "[]" operator on them, and you cannot modify them! StringBuffers behave more like the C++ string
• Arrays can be anonymous, e.g. a = new int[]{10, 7, 3, 1, 5}
• The try statement can have a finally clause
• If code can throw an exception derived from Exception but not RuntimeException, it must be wrapped in a try block that catches the exception, or the exception must be mentioned in the method's throws clause

If you come from a Java environment and have to learn C++, first ask why C++ instead of C# or plain C. Then reverse the above points.

Java vs. C#

Despite the name, C# is much, much, much closer to Java than to C++. Both C# and Java are actively evolving, and sometimes you have to look really closely to tell them apart:

But not everything about these languages is the same:

• C# has real closures; don't expect these in Java until at least Java 7.

Java EE and .NET

The two main platform for industrial-strength enterprise applications are Java EE (sometimes called just "Java") and .NET.