CSCI 255 — Java to C

This lab illustrates the similarities of Java and C.

Getting started using Java

Start NetBeans. Now create a project, using the menu choices File ⇒ New Project. At the New Project window select the project type Java Application and then press Finish.

Next delete the main method and replace it with the following.

    import java.util.Scanner ;

    public static void main(String[] args) {
        Scanner termInput = new Scanner(System.in);
        System.out.println("This is Java") ;
        System.out.println("Type in a small integer");
        int yourChoice = termInput.nextInt() ;
        for (int n = yourChoice; n>0; --n) {
            System.out.printf("%4d\n", n) ;
        }
        System.out.println("Blastoff!") ;
    }

Run the program and look at the output. Pretty boring.

Making C

Now we are going to write some C and C++. It won’t be as hard as you think. Start by creating a new NetBeans project. At the New Project menu create a C/C++ application within the C/C++ category.

You will need to use the little arrow on the side to specify that you are creating a C, rather than C++ or FORTRAN, application.

Copy the contents of Java’s main method into C’s main function. Do not copy the method header! Expect NetBeans to light up your C program.

At this point, we are going to go in lecture/lab mode. There are a few things to be done here.

• Use puts rather than System.out.println .
• Use printf rather than System.out.printf .
• Use scanf rather than the nextInt method. This one is a little trickier because it requires the use of C’s & (address-of) operator.
• Move the declaration of the variables! This is required only in older versions of C.

Making C++

Technically every C program is a C++ program, but let’s try to make a real C++ program. Again create a C/C++ application within the C/C++ category, but this time go with the default choice of C++ for the main file.

You can go ahead and replace the your C++ main with your C main. It won’t quite work, so try the following:

• Look at the C++ Files and Streams tutorial on tutorialspoint.
• Replace the calls of puts and printf with invocations of the overloaded << operator of C++’s ostream class. C++ allows operator overloading. Java does not.
• OK. You will also need to add include’s for fstream and iostream.
• Replace the call of scanf with an invocation of the overloaded >> operator of C++’s istream class.

That should be enough to get your program to run. The only problem is that n is not being print in the field of four characters. This requires adding an include for the iomanip class, a use of the setw method, and the magic of multiple inheritence.

        cout << setw(4) << n << endl ;

Finishing up