1  Java vs C

This document explains some differences between the C and Java languages.

Generally Java and C have a lot in common. In fact, C was a central criterion 
in designing the Java language.  Java adds several object oriented features 
of which C has none.  In a non technical sense, Java might be considered a 
superset of C, but it is slightly different on a few points.

2  Comments

Comments in C begin with "/*" and end with "*/". Any newlines that might happen to be 
between them are ignored like the rest of the text.  (Java accepts this type of comment too.)

3  The "public class..." keywords

Every Java file is enclosed by "public class classname {" and a closing brace "}". 
(These are required as part of Java s object orientation.) C programs do not include these.

4  Function declarations

When you declare a C function, you should not use the words "public static".  These words 
are required due to Java s object orientation features. An example C function is 

  /*
   * This is a C square function.
   */
  int square(int n) {
        return n * n;
  }

5  Variable declarations

All variable declarations for a C function must be at the top of the function.

6  Array declarations

An array in C is declared "eltType arrayName [arrayLength]". For example, to declare 
an array of thirty characters in C, you would type "char a [30]". Java syntax for 
this is very different.

7  Returning arrays

In Java, there is nothing wrong with returning an array. A C array declared in the 
form "char a [30]", however, should not be returned.  Returning an array in C requires 
pointers. You might have to allocate memory for it with a call to malloc(). The return 
type would be a pointer to a char; i.e., char *.

8  Array parameters

To have an array parameter, you would type "char a[]", not "char[] a" as in Java.

9  Array length

The array length of C arrays is not available using "a.length". You must pass the 
length as another parameter.

10  The boolean type

C does not include a boolean type. The int type can be used to make up for this. (C treats 
integers that are 0 as false and integers that are not 0 as true.)