2. Java Basics. 4. Java Classes

Август 4, 2022

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2. Java Basics. 4. Java Classes

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2. Class – why? Classes split application code to parts (from sophisticated to simple) Very often class
3. Class Description class name { // field declarations // method declarations } * Infopulse Training Center
4. Class Fields Class fields should be declared inside class out of all class methods Fields can
5. Defining Methods return_type method_name (parameter_list){ // method body } Example: int getFinalData(int a, int r){ int
6. Return Type The return type describes the value that comes back from the method A method
7. Parameters Any data type is possible for a parameter of a method Construct varargs is used
8. Constructors Constructor name should be the same as class name Constructor has no return type The
9. Objects Creating Object: class_name object_variable = new construtor_call; Declaring a Variable to Refer to an Object:
10. Using the this Keyword this is a reference to the current object The most common example:
11. Complex Numbers (1 of 4) Is it always possible to solve square equation within real numbers
12. Complex Numbers (2 of 4) Is it always possible to solve square equation within real numbers
13. Complex Numbers (3 of 4) Number of a + b * i type where a and
14. Complex Numbers (4 of 4) To add complex numbers use formula To multiply complex numbers use
15. Exercise 2.4.1. Create a class for saving and manipulating complex numbers. * Infopulse Training Center
16. Home Exercise 2.4.2 (1 of 2) 3D Vector is ordered sequence of 3 numbers (vector’s coordinates):
18. Скачать презентацию

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Class – why?
Classes split application code to parts (from sophisticated to

simple)
Very often class is a model of an object from the real world
Java says: Everything is an object
Class describes object behaviour
Class is a type

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Class Description
class name {
// field declarations
// method declarations
}
*
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Center

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Class Fields
Class fields should be declared inside class out of all

class methods
Fields can have primitive type, or reference type such as array or object
Fields are visible to all instance methods
Fields are automatically initialized (reference types with null, number types with zero, boolean – with false)

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$Defining Methods return_type method_name (parameter_list){ // method body } Example: int$

Defining Methods
return_type method_name (parameter_list){
// method body
}
Example:
int getFinalData(int a, int

r){
int b = r % 18;
return a * 2 + b;
}

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Return Type
The return type describes the value that comes back from

the method
A method can have void return type
Any method that is not declared void must contain a return statement with a corresponding return value
Return statements for void return type is not necessary

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Parameters
Any data type is possible for a parameter of a method
Construct

varargs is used to pass an arbitrary number of values (e.g. type... args)
Varargs can be used only in the final argument position
Parameters are passed into methods by value.
The values of the object's fields can be changed in the method

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Constructors
Constructor name should be the same as class name
Constructor has no

return type
The compiler automatically provides a no-argument, default constructor for any class without parameters – don’t use this possibility, declare such constructor explicitly
A class can have several constructors (with different sets of parameters)

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Objects
Creating Object:
class_name object_variable = new construtor_call;
Declaring a Variable to Refer to

an Object:
class_name object_variable;
Calling an Object's Methods:
object_variable.methodName(argumentList);

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Using the this Keyword
this is a reference to the current object
The

most common example:
class Point {
int x = 0;
int y = 0;
//constructor
Point(int x, int y) {
this.x = x;
this.y = y;
}
}

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Complex Numbers (1 of 4)
Is it always possible to solve square

equation within real numbers set?

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Complex Numbers (2 of 4)
Is it always possible to solve square

equation within real numbers set?
No, if it is impossible.
We can expand real number set to complex number set introducing new number type - complex unit i - in such a way:
i * i = -1

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Complex Numbers (3 of 4)
Number of a + b * i

type where a and b are real is called complex number.
Every square equation can be solved within complex numbers set.
Moreover, every algebraic equation (with arbitrary power) always can be solved within complex numbers set.

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