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.
OOP stands for Object-Oriented Programming.
Procedural programming is about writing procedures or methods that perform operations on the data, while object-oriented programming is about creating objects that contain both data and methods.
Object-oriented programming has several advantages over procedural programming:
Recursion is the technique of making a function call itself. This technique provides a way to break complicated problems down into simple problems which are easier to solve.
Recursion may be a bit difficult to understand. The best way to figure out how it works is to experiment with it.
In Java, variables are only accessible inside the region they are created. This is called scope.
Variables declared directly inside a method are available anywhere in the method following the line of code in which they were declared:
public class Main { public static void main(String[] args) { // Code here CANNOT use x int x = 100; // Code here can use x System.out.println(x);}}
With method overloading, multiple methods can have the same name with different parameters:
int myMethod(int x)
float myMethod(float x)
double myMethod(double x, double y)Consider the following example, which has two methods that add numbers of different type: Continue reading Java Method Overloading
In the previous page, we used the void keyword in all examples, which indicates that the method should not return a value.
If you want the method to return a value, you can use a primitive data type (such as int, char, etc.) instead of void, and use the return keyword inside the method: Continue reading Java Return
Information can be passed to methods as a parameter. Parameters act as variables inside the method.
Parameters are specified after the method name, inside the parentheses. You can add as many parameters as you want, just separate them with a comma.
The following example has a method that takes a String called fname as parameter. When the method is called, we pass along a first name, which is used inside the method to print the full name: Continue reading Java Method Parameters
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.
A multidimensional array is an array of arrays.
Multidimensional arrays are useful when you want to store data as a tabular form, like a table with rows and columns.
To create a two-dimensional array, add each array within its own set of curly braces:
int[][] myNumbers = { {1, 2, 3, 4}, {5, 6, 7} };
myNumbers is now an array with two arrays as its elements.
To demonstrate a practical example of using arrays, let’s create a program that calculates the average of different ages:
// An array storing different ages
int ages[] = {20, 22, 18, 35, 48, 26, 87, 70};
float avg, sum = 0;
// Get the length of the array
int length = ages.length;
// Loop through the elements of the array
for (int age : ages) {
sum += age;
}
// Calculate the average by dividing the sum by the length
avg = sum / length;
// Print the average
System.out.println("The average age is: " + avg);
And in this example, we create a program that finds the lowest age among different ages: Continue reading Java Arrays Examples