Simple Input and Output

We have also started on doing some simple input and output using Java, because a program is only useful if it can interact with users to get inputs to the program and produce output for the user to see.

In Java, there are 2 ways to perform input and output, namely through the command line and through GUI.

Command Line

• To perform an output to the command prompt window, you would use System.out.print() or System.out.println().
• To get an input from the user, you would use a Scanner class, as in the example program in Lab 1 Practice 4.
• You use entry.nextInt() to get an integer value, entry.nextDouble() to get a double value, and entry.nextLine() to get a string.

Graphical User Interface

• To perform an output to a GUI window, you would use the showMessageDialog() method in the JOptionPane class.
• To get an input from the user, you would use the showInputDialog() method, as in the example program in Lab 1 Practice 5.
• Do take note that getting input from the user in a GUI is a 2-step process. The input value is always captured as a String object and you need to convert it into the appropriate data types in the 2nd step.

Data in Programming

This week we started with basic programming in Java. First off, we need to understand the concept of Data in Programming.

Every computer program needs data to manipulate to make it useful. Data are values that the program uses when it is performing some mathematical calculation or simple using it as a counter for loops. Data are stored as variables in Java and we went through the way to declare variables in Java. Declaring variables ensures that the computer reserves memory storage areas for our variables. In declaring variables, the key thing to note is that every variable has to be associated with a data type, so that the computer knows how much memory space to allocate. Do read up Chapter 2 of the Johnson book to get more details of variable declaration and data types.

Some examples of variable declaration:

   double myLength, myDepth;
   int englishMarks;
   boolean isOK;

We have also seen how to perform arithmetic operations (+, -, *, /, %) in Java. Basically, arithmetic operations are evaluated the same way as in mathematics, with the exception of the '=' operator, which acts as the assignment operator. The assignment operator will take the result (value) of the evaluation on the right-hand-side and store it into the variable on its left-hand-side.

For example, in the program code:

   a = 2, b = 8, c = 4;
   answer = b * b - 4 * a * c;

the evaluation on the RHS will result in a value of 32 and this will be stored in the variable answer.

As usual, do leave comments if you have questions.

First Week

As with all first weeks of your life (and mine too, although its a little longer than yours 8-), its hectic and full of unknowns. Not knowing where the classrooms are, not knowing what the module is about, not knowing if the lecturer/s is/are good or not. Welcome to the real world. 8-)

As I have mentioned in the previous post, this blog will primarily contain the archive of the salient points of the module as we go along. I will strive to update it once a week, the keyword being strive. 8-) If you have any questions, please feel free to leave a comment so that we can all learn from each other.

Ok, for the first week, as it is only the start of the semester, we introduced the concept of programming and what writing computer programs is all about. Remember the PacMan game that I mentioned, as an example of a simple computer program? Right, so:

• a computer program is simply a set of instructions that you give to the computer for it to perform some actions for you,
• programming languages are the languages used to 'talk' or 'tell' the instructions to the computer,
• Java is just one of the many programming languages

So in the weeks to come, we will be learning the syntax, or the rules, of the Java programming language, as well as the logic, or algorithm, of computer programming so that we can write useful computer programs.

We also started with Lab 1 on writing simple logic or algorithms, in pseudo codes, to get our brains to think logically so that we can later formulate the logic into Java codes to program into the computer. The key thing to note in writing pseudo codes (whether using pen and paper or mentally in your brain) is to try to be as explicit and clear as possible. Remember that the computer cannot think, so it will not be able to do intelligent actions for you unless you instruct it to. Hence instructions, in the form of pseudo codes, need to be thorough and clear.

In the lab, we wrote (or at least you, I have written mine long ago 8-) our first Java program, HelloWorld.java, using TextPad and JDK. Do remember these steps on writing a Java program, as you will be doing this on your own from next week onwards.

• Open TextPad and type in your Java codes.
• Save the file as .java.
• Open up a command prompt window and navigate to the folder where you saved the Java file.
• Use the command: javac .java to compile the Java program.
• Use the command: java to run the Java program to see if it works according to what you want it to work.

Do leave comments if you have questions on what was covered this week!

Welcome!

This is the first post for the IT1838 mPowered blog!

The orientation is starting next week from 2 April to 5 April and semester will start on 16 April. This new semester we will do something different from other semesters, and I intend to use this blog to document down the salient points discussed in the lectures and the labs. This not only serves as an archive, for you to refer to when you study for your exam (yes, this module is examinable) but also as a communication platform for us to exchange ideas on the module.

And since this is the first post, I will not bore you with what the module is about. 8-)

Enjoy your stay in NYP!