Object oriented programming>OOP👌👍🏿

LESSON 3

ASSIGNMENT
✅> Every variables is assigned data type that designates the type and quantity of value it can hold.
✳️<> as many of you guess , variable is a name given to a memory location.

⚜️During declaration of a variable, we nedd to take care of two things
1. Dataype
2. Dataname

Similarly , we can initialize variables by assigning values in two ways:
1.variable initialization//
2. Assigning value by taking input from user//

/look the snippet code below with different dataypes and initializations

public class Firsta {

  public static void main(String[] args) {
    long x = 2345267;
    float y =3.45f;
    boolean z = true;
    char ch = '@';
    String str ="learn to code!!";
        
    
        
    
    System.out.println("the number is: " +x);
    System.out.println(y);
      System.out.println(z);
      System.out.println(ch);
      System.out.println(str);

Exam sample, AAU[ Java] , share ⚜️it please

LESSON 4:
IMPORTING SCANNER CLASS IN | JAVA
👨🏽‍💻Scanner is a class in java.util package used for obtaining the input of the primitive types like int, double, etc. and strings.

✳️To read numerical values of a certain data type XYZ, the function to use is nextXYZ().
✅ To read strings, we use nextLine().

🔱To read a single character, we use next().charAt(0). next() function returns the next token/word in the input as a string and charAt(0) function returns the first character in that string.



import java.util.Scanner;

public class Firsta {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);
System.out.println("enter some String");

String name = scanner.nextLine();


System.out.println("enter your age");
int x = scanner.nextInt();
scanner.nextLine();
System.out.println("what is you departent? ");
String dep =scanner.nextLine();



System.out.println("your name is: "+name);

System.out.println("your age is:"+ x);

System.out.println("your in "+dep+" departement now!");



}

}

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LESSON 5:
JAVA MATH:

⚜️The Java Math class has many methods that allows you to perform mathematical tasks on numbers.
✳️The Math.sqrt(x) method returns the square root of x.

✳️The Math.max(x,y) method can be used to find the highest value of x and y.

✳️ The Math.abs(x) method returns the absolute (positive) value of x.

❤️ Math.random() returns a random number between 0.0 (inclusive), and 1.0 (exclusive).

public class Firsta {

  public static void main(String[] args) {
    double x,y,z;
    
      /*double x = 3.14;
      double y = 3.41;
      
      double z = Math.max(x, y);
      double a = Math.sqrt(5);
      double ab = Math.ceil(x);// maximum number
      double ac = Math.floor(y);// minimum number
      System.out.println(z);*/
     System.out.println(a);
      System.out.println(ab);

‼️THERE ARE ALOT OF METHODS IN JAVA FOR FURTHER MATHEMATICAL OPERATIONS
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LESSON 6: ARRAY AND 2D ARRAYS

✅An array is a collection of items stored at contiguous memory locations. The idea is to store multiple items of the same type together.
✳️Multidimensional Arrays can be defined in simple words as array of arrays. Data in multidimensional arrays are stored in tabular form (in row major order).
*In the array there will be:
data_type : type of data to be stored in the array
dimension: the dimension of the array is created. like 1D, 2D ...
array_name: name of the array
finally , the size of the array.
#example_of_array:;
class CODER
{
public static void main (String[] args)
{
// declares an Array of integers.
int[] arr;

// allocating memory for 5 integers.
arr = new int[5];

// initialize the first elements of the array
arr[0] = 10;

// initialize the second elements of the array
arr[1] = 20;

//so on...
arr[2] = 30;
arr[3] = 40;
arr[4] = 50;

// accessing the elements of the specified array
for (int i = 0; i < arr.length; i++)
System.out.println("Element at index " + i +
" : "+ arr[i]);
}
}


2D array:-

class Learn {
public static void main(String[] args)
{

int[][] arr = new int[10][20];
arr[0][0] = 1;

System.out.println("arr[0][0] = " + arr[0][0]);
}
}

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java student guide 2

‼️: ignore [a], [b],[c] and [d] it is only to identify the choice

LESSON 7:
LOOPS AND NESTED LOOPS
✳️Looping in java helps by facilitating the execution of of a set of instructions repeatedly while some condition evaluates to true.

1. While-loops: allows the code to be executed repeatedly based on a given Boolean condition.

   while (boolean condition)
     {
   loop statements...
   }

2. for-loops: unlike while statement, it consumes the initialization, condition, and increment/decrement.
for (initialization condition; testing condition;
increment/decrement)
{
statement(s)
}

3. do-while: do while loop is similar to while loop with only difference that it checks for condition after executing the statements.
do
{
statements..
}
while (condition);

sample example for for-loop:

public class Loops
{
    public static void main(String[] args)
    {
        ArrayList<Integer> ar = new ArrayList<>();//we will see about list in the next lessons
        for (int i = 0; i < Integer.MAX_VALUE; i++)
        {
            ar.add(i);
        }
    }

}


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#different looping structures in java👌🏻