Java Programming with Java 8 and OCA OCP Java Exam Prep

All the source files used throughout the course is here:

Creating variables and assigning values.

Running our very first application.

Throughout the course you will need to import some projects into the workspace of Eclipse. Thats why you need to learn how to import a project from external source and then export your own code.

Importing means: Using the pre-developed code in your very own development environment.

Exporting means: Packaging the source code of your application so that anyone else can use your code.

Primitives are the exceptions of object oriented Java. Apart from the objects, they don't have any methods, they can not be pass by address value etc. (May not make sense for now, just be familiar with the terms) They are simply used for storing some basic (primitive values).

Simple primitive values are: int, float, long, short, char, boolean.

You will do some mathematical operations on primitive variables.

int is the most known integer type in Java. In case you need to store much greater values, you need to use long type. Because its range is much more greater than int's.

If you will store tiny numbers (namely smaller than 256) you may use short type not to consume more memory.

According to the needs, you may use short, int and long types to represent integer values. In some cases you may need to use them together. In that case you should convert them properly.

Type casting means converting different types to each other and accepting possible data loses so that compiler does not complain about these possible data loses.

You are given heterogenous type of variables in this exercise.

You need to cast the types for acquiring a single result with desired type. Good challenge!

We represent floating point numbers with float and double types.

Default floating point type is double and its range is so wide.

If you will store tinier floating point numbers, you may use float type.

In this case you should append "f" next to each floating point number. Otherwise they will be converted to double automatically.

Mathematical operations have precedence order by default. If you don't change the precedence order will be

1- Multiplication, division, modulus

2- Summation and subtraction

Group 1 and group 2 is executed from left to right among each other.

You will learn

• +=, -=, *=, /= and %= operators for quick arithmetic and assignment
• ++ and -- operators for quick increment and decrement o f a value by 1

Processors run with boolean algebra. Everything is 0 or 1 or ( true or false)

In any software, you control the execution flow with true and false values also.

True and false values are represented with boolean type.

You will learn boolean types and boolean arithmetics.

Boolean type is a truth-value and denoted by only one bit (0 or 1). In that case, an expression is either true or false. Sometimes we need to combine some values to yield a combined result. Combining operation is done with Boolean algebra. For instance;

“The customers subscribed in last three months who did not pay the bill this month” expression has two boolean values inside:

1. The customers who subscribed in last three months

2. The customers who did not pay the bill.

This expressions can be combined by an and operation: expr1 and not expr2 if 1. expr1: The customers who subscribed in last three months 2. expr2: The customers who did pay the bill. Boolean algebra operations are the conjunction and, the disjunction or, and the negation not. In java, AND operation is denoted by &&, OR operation || and NEGATION operation by ! .

You may write a value into console with

System.out.print() and System.out.println() methods. You may pass any object instance into this method so that they can be represented as String (text).

print and println methods have a simple difference: println methods put a new line character at the end so that lines are broken.

We represent a single character with char type.

Char is an integer corresponding to its ASCII value in fact. So you can change a char variable's value such as an ordinary integer. This is called as char arithmetic:

A char is an integer between 0 and 65535 implicitly. For instance the code below prints A.

char c = 65;

System.out.println(c);

If you increment c by 1, this code will print B.

You will have an hands-on experience with character arithmetic now.

When we need to modify the flow according to a condition, we may use if statements. If a Boolean expression is true, we may do something, else something different. This can be visualized with a flow chart.

You will learn how to construct a flow chart and then implement them with if-else blocks.

We will develop an evaluating system for students.

Create a variable to store the exam result.

Our system will print the letter grade according to the

table below such as “Your grade is B for 56.” If the point smaller than 60, system will print “You

may re-attend the exam.”, otherwise “Thanks for attending the exam.”

Switch statement is the alternative to if-else blocks.

If else statements control the execution flow with boolean values. But switch statements control the execution flow with integer, string or enum values.

•Loops is used to do similar thing several times not to copy-paste code several times.

•Loops can be executed as long as a condition is true and can be stopped when this condition is not satisfied.

•Each execution of the same statement is called as “iteration”.

"while" loop is the alternative to for loop.

With while loop you only need to define the termination condition.

This exercise is a common and well-known exercise for every programming language:

Drawing some shapes with * character and combination of for loops.

In some specific cases you may need to end the execution of a for loop. In that case you use break statement.

Nested loops: Loop inside a loop

Nested loops are being used inside in most of the applications.

You can use a loop inside a loop or you may use them sequentially. Their boundaries might be completely independent from each other or their boundaries may change according to each other.

• Array is a series of primitive variables or object instances.
• Used for multiple values with the same type.
• Stored in heap space.
• Defined with this syntax:
• type [];

•You may initialize the array upon the allocation of memory with this syntax:

•int x [] = new int[] {1,-1,9,0,5};

• If x is the starting address of an array;
• arr[0] => x
• •arr[2] => skip 2 in items from the beginning of the array. 32 bits each.
• So add 2*32 bits to the beginning address => go to x +64
• Read size of int bytes from there. So read 4 bytes and get the value.
• When you try to access a memory beyond of the array, you get this exception. Because the memory block you are trying to access is out of bounds of the array.

•We can use for and while loops to traverse a loop. Length of an array can be accessed by length attribute of array.

int myGreatArray[] = new int[10];

for(int i = 0; i < myGreatArray.length; i++){

System.out.println(myGreatArray[i]);

}

All tabular data can be represented as arrays of arrays. They are called as multi-dimensional array.

Board games like chess, match-results table of a football league, sales data over months, seat plan of a bus...

Every row means a separate array.

• Object is anything abstract or concrete you can “define” with some attributes and/or behaviors. Eg:

Bicycle: Is an object with two tiers, paddles and a seat.

Human: Is an object with a torso, two legs, two arms, a head and speaking, thinking behaviors.

Love: Is an object between two human that can last forever or may end quickly.

• Class is the package of some attributes (values related to an object) and some behaviours.

• Instance is the real object with flesh and blood, allocating some memory to store its individual values.

  
  

For creating an instance in Java, "new" keyword is used. When you create an instance enough memory is allocated in JVM and starting address of the instance returns a reference.