Programming I Pre-Lab Activities

Reading

Compiling, Running, and Logic: These three actions are what constitute a working program. If the program can compile, run, and the logic is right, then the program works. Compiling is the process of transforming a persons higher-level code (like Java or Python) into machine code for the computer to read. If the code is converted properly and the computer can read the code, then the code compiles! What this means is that the computer was able to properly read the information and verify that the code should be able to work. After the computer has done this, then the program is ready to run. When running the program, the code is executed by the computer and an output is presented given that there are on errors during the run. The output can then be examined for logical accuracy, which is the final step to ensure if your code works properly. Does your program do what you intended it to? If so, then it is logically correct.

Primitive Data: There are various types of data in Computer Science, and primitive happens to be one of the simplest in high-level programming languages. Oftentimes, this data can be equated to numbers. There are eight types of primitive data in java:

1. Integers (int): Whole numbers, zero, and negative numbers are included. Numbers like -2, -1, 0, 1, 2

2. Booleans (boolean): A value which can be set to true or false

3. Characters (char): A single character like 'a', 'b', '1', or 'G' which has a unique position in memory

4. Double (double): Decimal numbers which have more decimal places but less of a maximum magnitude compared to floats

5. Float (float): Decimal numbers

6. Short (short): Integer values which have a smaller range compared to int

7. Long (long): Integer values which have a larger range compared to int

8. Byte (byte): Character versions of numbers from -128 to 127.

Each of these data types has their own special applications. You can convert each of these types of data as long as they are similar. If you convert from a data with more storage to one with less storage, then you must cast, otherwise, you can convert freely. For example...

double num = 6.0;

num = 5;

//5 is an int, but there is automatic casting because an int is of less size than a double.

int num2 = 6

num2 = (int)5.8;

/*This works and sets num2 to equal 5 after it is casted as an int. It must be casted because an int is

of less storage than a double.*/

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Here is what it looks like to declare two different integer variables in a Java main method:

public static void main(String[] args) {

int a;

int b = 2;

}

* The first is simply a declaration that it exists without assignment to a value, while the second has a value assigned to it.

Lets say we wanted a to have a value... here is how we would give it one:

public static void main(String[] args) {

int a;

int b =2;

a = 4

}

And then lets say we want to change the value of b into the value of a if the value of a is larger than b. We would do so using an if-statement. It would look like this:

public static void main(String[] args) {

int a;

int b =2;

a = 4

if (a > b) {

b = a;

}

}

In this program, both b and a are now 4.

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Now that we have done a little basic introductory programming, review the mini lab below to download BlueJ and create a test program.