DEV Community: Ilakkiya

ARRAY

Ilakkiya — Tue, 18 Feb 2025 05:03:50 +0000

Arrays are fundamental structures in Java that allow us to store multiple values of the same type in a single variable. They are useful for storing and managing collections of data.Arrays are index based.
Basics of Arrays in Java

There are some basic operations we can start with as mentioned below:

Array Declaration

To declare an array in Java, use the following syntax:

type[] arrayName;

type: The data type of the array elements (e.g., int, String).
arrayName: The name of the array.

Note: The array is not yet initialized.

Create an Array

To create an array, you need to allocate memory for it using the new keyword:

// Creating an array of 5 integers
int[] numbers = new int[5];

This statement initializes the numbers array to hold 5 integers. The default value for each element is 0.

Access an Element of an Array

We can access array elements using their index, which starts from 0:

// Setting the first element of the array
numbers[0] = 10; 

// Accessing the first element
int firstElement = numbers[0];

The first line sets the value of the first element to 10. The second line retrieves the value of the first element.

Change an Array Element

To change an element, assign a new value to a specific index:

// Changing the first element to 20
numbers[0] = 20;

Array Length

We can get the length of an array using the length property:

// Getting the length of the array
int length = numbers.length;

REFERENCE:https://www.geeksforgeeks.org/arrays-in-java/

PROGRAM:

public class Marks
{
public static void main(String args[])
{
int[] marks={96,92,65,89,93};
System.out.println(marks.length);
int i=0;
int total=0;
while(i<marks.length)
{
System.out.println(marks[i]);
total=total+marks[i];
i++;
}
System.out.println(total);
System.out.println(total/marks.length);
}
}

OUTPUT:

length:5
mark:96
mark:92
mark:65
mark:89
mark:93
Total:435
percentage:87

Puzzle Task:

Ilakkiya — Tue, 04 Feb 2025 12:37:23 +0000

program1:

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

int beat=1024;
int count=0;
while(beat>1)
{
beat=beat/2;
count=count+1;
}
System.out.println("total counts:" +count);
}
}

output=>total counts:10

program2:

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

int flower=1;
int count=1;
while(count<=7)
{
flower=flower*2;
count=count+1;
}
System.out.println("total flowers" +flower);
}
}

output=> total flowers:128

control flow statement:

Ilakkiya — Sun, 02 Feb 2025 14:40:39 +0000

CONTROL FLOW STATEMENT:

Java compiler executes the code from top to bottom. The statements in the code are executed according to the order in which they appear. However, Java provides statements that can be used to control the flow of Java code. Such statements are called control flow statements. It is one of the fundamental features of Java, which provides a smooth flow of program.

Loop statements

do while loop
while loop
for loop
for-each loop

while loop:

The while loop is also used to iterate over the number of statements multiple times. However, if we don't know the number of iterations in advance, it is recommended to use a while loop. Unlike for loop, the initialization and increment/decrement doesn't take place inside the loop statement in while loop.

It is also known as the entry-controlled loop since the condition is checked at the start of the loop. If the condition is true, then the loop body will be executed; otherwise, the statements after the loop will be executed.

SYNTAX:
while(condition)
{

//looping statements;

}

FLOWCHART:

Image description

EXAMPLE PROGRAM:

public class Calculation {

public static void main(String[] args) {

int i = 0;

System.out.println("Printing the list of first 10 evennumbers");

while(i<=10) {

System.out.println(i);

i = i + 2;

}

}

}

output:
Printing the list of first 10 evennumbers
0
2
4
6
8
10

TASK1:

program:

public class Count
{

public static void main(String args[]) 
        {
    int count=1;
        while(count<=5) 
               {
         count=count+1;
         System.out.println("count:  " +count);
       }
      }

}

output:
count: 2
count: 3
count: 4
count: 5
count: 6

TASK2:

program:

public class Count1
{
public static void main(String args[])
{
int count=5;
while(count>=1)
{
count=count-1;
System.out.println("count: "+count);
}
}
}

output:
count: 4
count: 3
count: 2
count: 1
count: 0

TASK3:

program:

public class Count2
{
public static void main(String args[])
{
int count=1;
while(count<=10)
{
count=count+2;
System.out.println("count: "+count);
}
}
}

output:
count: 3
count: 5
count: 7
count: 9
count: 11

TASK4:

program:

public class Count3
{
public static void main(String args[])
{
int count=0;
while(count<10)
{
count=count+2;
System.out.println("count: "+count);
}
}
}

output:
count: 2
count: 4
count: 6
count: 8
count: 10

SWITCH STATEMENT AND TERNARY:

Ilakkiya — Sun, 02 Feb 2025 14:05:42 +0000

1. SWITCH STATEMENT:

The switch statement in Java is a multi-way branch statement. In simple words, the Java switch statement executes one statement from multiple conditions.

It is an alternative to an if-else-if ladder statement. It provides an easy way to dispatch execution to different parts of code based on the value of the expression. The expression can be of type byte, short, char, int, long, enums[TBD], String, or wrapper classes (Integer, Short, Byte, Long).

Note: Java switch expression must be of byte, short, int, long(with its Wrapper type), enums and string. Beginning with JDK7, it also works with enumerated types (Enums in java), the String class, and Wrapper classes.[TBD]

SYNTAX:
switch(expression)
{
case value1 :
// Statements
break; // break is optional

case value2 :
// Statements
break; // break is optional
....
....
....
default :
// default Statement
}
//Break-It will moves to next statement.

FLOWCHART:

EXAMPLE PROGRAM:

public class Days {
public static void main(String[] args)
{
int day = 5;
String dayString;
switch (day)
{
case 1:
dayString = "Monday";
break;
case 2:
dayString = "Tuesday";
break;
case 3:
dayString = "Wednesday";
break;
case 4:
dayString = "Thursday";
break;
case 5:
dayString = "Friday";
break;
case 6:
dayString = "Saturday";
break;
case 7:
dayString = "Sunday";
break;
default:
dayString = "Invalid day";
}
System.out.println(dayString);
}
}

output:Friday

2.TERNARY STATEMENT:

In Java, the ternary operator is a type of Java conditional operator.

The ternary operator (? :) consists of three operands. It is used to evaluate Boolean expressions. The operator decides which value will be assigned to the variable. It is the only conditional operator that accepts three operands. It can be used instead of the if-else statement. It makes the code much more easy, readable, and shorter.

Note: Every code using an if-else statement cannot be replaced with a ternary operator.

SYNTAX:

variable = (condition) ? expression1 : expression2

The above statement states that if the condition returns true, expression1 gets executed, else the expression2 gets executed and the final result stored in a variable.

FLOWCHART:

EXAMPLE PROGRAM:

public class TernaryOperator
{

public static void main(String args[])

{

int x, y;

x = 20;

y = (x == 1) ? 61: 90;

System.out.println("Value of y is: " + y);

y = (x == 20) ? 61: 90;

System.out.println("Value of y is: " + y);

}

}

output:
Value of y is: 90
Value of y is: 61

REFERENCE:
https://www.javatpoint.com/java-switch
https://www.geeksforgeeks.org/switch-statement-in-java/

if,if else..,nested if statement:

Ilakkiya — Thu, 30 Jan 2025 18:27:56 +0000

1.Java if statement:

The if statement is the most simple decision-making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e. if a certain condition is true then a block of statements is executed otherwise not.

Syntax:

if(condition)  { 

  // Statements to execute if   

 // condition is true 


}

Flowchart:

Example:

public class Demo
{
  public static void main(String args[])
   {
    int i = 10;
    if (i < 15)
        System.out.println("10 is less than 15");
   }
}
output:10 is less than 15

2.Java if else statement:

The if-else statement helps you to run a specific block of a program if the condition is true or else, it will check other conditions.

Syntax:

If(condition){

// code if condition is true

}else{

//code if condition is false

}

Flowchart:

Example:

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

int age=21;
if(age>22)
{
System.out.println("Idhaya's age is 21");
}
else
{
System.out.println("Ilakkiya's age is 21");
}
}
}
output:Ilakkiya's age is 21

3.Java Nested if statement:

Nested if in Java refers to having one if statement inside another if statement. If the outer condition is true the inner conditions are checked and executed accordingly.

Syntax:

if (condition1) {

    if (condition2) {

        if (condition3) {

            // statements;


     }
   }
 }

Flowchart:

Example:
public class Equal
{
public static void main(String args[])
{
int a = 10;
int b = 20;
if (a == 10)
{
if (b == 20)

{
System.out.println("satisfied");
}
}
}
}
output:satisfied

TASK:
1.#Java program for if statement:

public class Mark
{
public static void main(String args[])
{
int mark=50;
if(mark>35)
System.out.println("passed");
}
}
output: passed

python program for if statement:

mark=50
if(mark>35):
print("passed")
Output: passed

2.#Java program for if else statement:

public class Fruit
{

public static void main(String args[])
{
int orange=100;
if(orange>200)
{
System.out.println("will not buy");
}
else
{
System.out.println("will buy oranges");
}
}
}
Output: will buy oranges

python program for if else statement:

orange=100
if(orange>200):
print("will not buy")
else:
print("will buy oranges")
Output:
will buy oranges

Java program for nested if statement:

public class Calculate
{
public static void main(String args[])
{
int a = 10;
int b = 20;
if (a==10)
{
if (b>10)
{
System.out.println("true");
}
else
{
System.out.println("false");
}
}
}
}

output:true

python program for nested if statement:

a = 10
b = 20
if a == 10:
if b > 10:
print("true")
else:
print("false")

output:true