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JAVA LOOP
• In computer programming, loops are used to repeat a block of code. For
example, if you want to show a message 100 times, then rather than typing the
same code .

Types of LOOPS
• in Java, there are three types of loops: for, while, and do-while. The for loop is
used for a known number of iterations, the while loop is used for an unknown
number of iterations based on a condition, and the do-while loop is similar to the
while loop, but the code block is executed at least onceV

For loop
• Java for loop is used to run a block of code for a certain number of times. The
syntax of for loop is:
for (initialExpression; testExpression; updateExpression) {
// body of the loop
}

For loop
The initial expression initializes and/or
declares variables and executes only once.
The condition is evaluated. If the condition is
true, the body of the for loop is executed.
The update Expression updates the value of
initialExpression.
The condition is evaluated again. The process
continues until the condition is false.

Example 1:
int n = 5;
// for loop
for (int i = 1; i <= n; ++i) {
System.out.println("Java is fun");
Output:
Java is fun
Java is fun
Java is fun
Java is fun
Java is fun

Example2:
Java for loop
for(int i=1;i<=10;i++){
System.out.println(i);
}
Output:
1
2
3…. 10

Java while loop
• The Java while loop is used to iterate a part of the program repeatedly until the
specified Boolean condition is true. As soon as the Boolean condition becomes
false, the loop automatically stops.
• The while loop is considered as a repeating if statement. If the number of iteration
is not fixed, it is recommended to use the while loop.

While syntax
while (condition){
//code to be executed
Increment / decrement statement
}

example1
1. int i=1;
2. while(i<=10){
3. System.out.println(i);
4. i++;
5. }
Output:
1
2
3... 10

Java while loop
Java while loop is used to run a specific code until a certain condition is met. The
syntax of the while loop is:

A while loop evaluates the textExpression inside the parenthesis ().
If the textExpression evaluates to true, the code inside the while loop is executed.
The textExpression is evaluated again.
This process continues until the textExpression is false.
When the textExpression evaluates to false, the loop stops.
To learn more about the conditions, visit Java relational and logical operators.

Example 1:
// declare variables
int i = 1, n = 5;
// while loop from 1 to 5
while(i <= n) {
System.out.println(i);
i++;
Output:
1
2
3…5

Syntax
while (condition){
//code to be executed
Increment / decrement statement
}

Example 1:
1. int i=1;
2. while(i<=10){
4. i++;
5. }

Java do-while Loop
• The Java do-while loop is used to iterate a part of the program repeatedly, until
the specified condition is true. If the number of iteration is not fixed and you must
have to execute the loop at least once, it is recommended to use a do-while loop.
• Java do-while loop is called an exit control loop. Therefore, unlike while loop
and for loop, the do-while check the condition at the end of loop body. The
Java do-while loop is executed at least once because condition is checked after
loop body.

Syntax
1.do{
2.//code to be executed / loop body
3.//update statement
4.}while (condition);

1. int i=1;
2. do{
4. i++;
5. }while(i<=10);
Output:
1
2
3…10

Java Arrays
• Arrays are used to store multiple values in a single variable, instead of
declaring separate variables for each value.
• To declare an array, define the variable type with square brackets:

Array
String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
To create an array of integers, you could write:
int[] myNum = {10, 20, 30, 40};

Example 1
public static void main(String[] args) {
System.out.println(cars[0]);
}

cars[0] = "Opel";
System.out.println(cars[0]);

for (int i = 0; i < cars.length; i++) {
System.out.println(cars[i]);
Output:
Volvo", "BMW", "Ford", "Mazd

JAVA METHOD
• A method is a block of code which only runs when it is called.
• You can pass data, known as parameters, into a method.
• Methods are used to perform certain actions, and they are also known as functions.
• Why use methods? To reuse code: define the code once, and use it many times.
Create a Method
• A method must be declared within a class. It is defined with the name of the method, followed
by parentheses (). Java provides some pre-defined methods, such as System.out.println(), but
you can also create your own methods to perform certain actions:

int[][] myNumbers = { {1, 2, 3, 4}, {5, 6, 7} };
System.out.println(myNumbers[1][2]); // Outputs 7

Scanner input = new Scanner (System.in);
double totalprice=0;
for (int i=0; i <cars.length ; i++)
{
System.out.println(cars[i]);
System.out.println("Enter price:");
double price = input.nextDouble();
totalprice=(totalprice + price);
}
System.out.println("TOTAL PRICE:" + totalprice);

int[] age = {12, 4, 5, 2, 5};
// access each array elements
System.out.println("Accessing Elements of Array:");
System.out.println("First Element: " + age[0]);
System.out.println("Second Element: " + age[1]);
System.out.println("Third Element: " + age[2]);
System.out.println("Fourth Element: " + age[3]);
System.out.println("Fifth Element: " + age[4]);
}

Example Explained
myMethod() is the name of the method
static means that the method belongs to the Main class and not
an object of the Main class. You will learn more about objects
and how to access methods through objects later in this
tutorial.
void means that this method does not have a return value. You
will learn more about return values later in this chapter

Call a Method
To call a method in Java, write the method's name followed by two parentheses ()
and a semicolon;
In the following example, myMethod() is used to print a text (the action), when it is
called:

Inside main, call the myMethod() method:
public class Main {
static void myMethod()
{
System.out.println("I just got executed!");
}
public static void main(String[] args)
{
myMethod();
}
}

Creating your own Classes
At the end of the lesson, the student should be able to:
• ● Create their own classes
• ● Declare attributes and methods for their classes
• ● Use the this reference to access instance data
• ● Create and call overloaded methods
• ● Import and create packages
• ● Use access modifiers to control access to class members
•

Java Classes/Objects
• Java is an object-oriented programming language.
• Everything in Java is associated with classes and objects, along with its
attributes and methods. For example: in real life, a car is an object. The car
has attributes, such as weight and color, and methods, such as drive and
brake.
• A Class is like an object constructor, or a "blueprint" for creating objects.

What is the main class in
NetBeans?
A NetBeans project contains the classes needed to build a Java application. The application uses the main
class as the starting point for the execution of the Java code. In fact, in a new Java application project
created by NetBeans only one class included - the main class contained within the Main. java file.DELA
PEÑA, CARL CUEVAS?

get method
The get method returns the value of the variable name . The set method takes
a parameter ( newName ) and assigns it to the name variable. The this keyword
is used to refer to the current object.

get method
• The get method returns the value of the variable name . The set method takes a
parameter ( newName ) and assigns it to the name variable. The this keyword is
used to refer to the current object.

• Defining your own classes
• Coding Guidelines
• Declaring Attributes
• Instance Variables
• Class (static) variables
• Declaring Methods
• Accessor Methods
• Mutator Methods
• Multiple return statements
• Static Methods
• “this” reference
• Overloading Methods
• Constructors
• Default Constructor
• Overloading Constructors
• Using Constructors
• “this()” constructor call
• Packages
• Importing Packages
• Creating Packages
• Setting the CLASSPATH
• Access Modifiers
• default accessibility
• public accessibility
• protected accessibility
• private accessibility

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