05. Java Loops Methods and Classes

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Loops, Methods, Classes
Using Loops, Defining and Using
Methods, Using API Classes,
Exceptions, Defining Classes
Svetlin N...

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1. Loops
 while, do-while, for, for-each
2. Methods
 Defining Methods
 Invoking Methods
3. Using the Java API Classes...

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 The "Java Basics" course is NOT for absolute beginners
 Take the "C# Basics" course at SoftUni first:
https://softuni...

Loops

Loop: Definition
 A loop is a control statement that repeats the execution of a
block of statements
 May execute a code ...

While Loop
 The simplest and most frequently used loop
 The repeat condition
 Returns a boolean result of true or false...

While Loop – Example: Numbers 0…9
int counter = 0;
while (counter < 10) {
System.out.printf("Number : %dn", counter);
coun...

Using the break Operator
 The break operator exits the inner-most loop
public static void main(String[] args) {
int n = n...

Do-While Loop
 Another classical loop structure is:
 The block of statements is repeated
 While the boolean loop condit...

Product of Numbers [N..M] – Example
 Calculating the product of all numbers in the interval [n..m]:
Scanner input = new S...

 The classical for-loop syntax is:
 Consists of
 Initialization statement
 Boolean test expression
 Update statement
...

 A simple for-loop to print the numbers 0…9:
For Loop – Examples
for (int number = 0; number < 10; number++) {
System.out...

 continue bypasses the iteration of the inner-most loop
 Example: sum all odd numbers in [1…n], not divisors of 7:
Using...

 The typical for-each loop syntax is:
 Iterates over all the elements of a collection
 The element is the loop variable...

 Example of for-each loop:
 The loop iterates over the array of day names
 The variable day takes all its values
 Appl...

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 Loops can be nested (one inside another)
 Example: print all combinations from TOTO 6/49 lottery
Nested Loops
for (i...

Loops
Live Demo

Methods
Defining and Invoking Methods

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 Methods are named
pieces of code
 Defined in the class
body
 Can be invoked
multiple times
 Can take parameters
 ...

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Methods with Parameters and Return Value
static double calcTriangleArea(double width, double height) {
return width * h...

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 Recursion == method can calls itself
Recursion
public static void main(String[] args) {
int n = 5;
long factorial = c...

Methods
Live Demo

Using the Java API Classes

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 Java SE provides thousands of ready-to-use classes
 Located in packages like java.lang, java.math, java.net,
java.io...

Using the Java API Classes
Live Demo

Exception Handling Basics
Catch and Throw Exceptions

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 In Java exceptions are handled by the try-catch-finally
construction
 catch blocks can be used multiple times to pro...

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Handling Exceptions – Example
public static void main(String[] args) {
String str = new Scanner(System.in).nextLine();
...

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 A method in Java could declare "throws SomeException"
 This says "I don't care about SomeException", please re-throw...

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 When we use a resource that is expected to be closed, we use the
try-with-resources statement
Resource Management in ...

Defining Simple Classes
Using Classes to Hold a Set of Fields

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 Classes in Java combine a set of named fields / properties
 Defining a class Point holding X and Y coordinates:
Defi...

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 Eclipse provides tools
for automatically
generate constructors
and getters / setters
for the class fields
Defining Cl...

Defining Simple Classes
Live Demo

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 Java supports the classical loop constructs
 while, do-while, for, for-each
 Similarly to C#, JavaScript, PHP, C, C...

?
https://softuni.bg/courses/java-basics/
Loops, Methods, Classes

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 This course (slides, examples, demos, videos, homework, etc.)
is licensed under the "Creative Commons Attribution-
No...

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