Difference Between For and While loop in Java

Both for and while loops play significant roles in the Java programming language. When a programmer knows in advance how many times iterations will run, they should use a for loop; otherwise, a while loop is more appropriate.

Sno.	For Loop	While Loop
1	Initialization, test condition, and update expression are part of the loop header.	Initialization, test condition, and update expression are written separately.
2	We can initialize the variable in the loop header.	We cannot initialize the variable in the loop header.
3	In the for loop, we know in advance how many times the loop will run.	It is used when the number of iterations is not known.
4	Syntax: `for (initialization; condition; increment/decrement) { }`	Syntax: `while (condition) { }`
5	Increment and decrement are part of the loop header.	Increment and decrement are not part of the loop header. They must be done inside the loop body.
6	Ideal for iterating over arrays or collections.	Useful for reading data or continuing until a condition is met.
7	Condition is checked before entering the loop.	Condition is checked before each iteration of the loop.

While loop

In the while loop, initialization is done outside the loop, and the update expression is written inside the loop body. If we use the update variable in the loop condition and do not update it inside the while loop, an infinite loop will be created. To avoid this, we update the variable inside the loop. The loop body executes as long as the condition remains true. When the condition becomes false, the loop body is skipped, and control is transferred to the next executable statement in the program.

Syntax:

while (condition) {
    // Code to be executed repeatedly
}

The while keyword is used to create a while loop, followed by a condition within parentheses (condition) and then curly braces {}. The loop body is written inside the curly braces.

Flowchart

Explanation:

The condition is checked first in the flowchart.
If the condition is true, the loop body is executed.
The loop will continue to run until the condition becomes false.
When the condition becomes false, the loop body is skipped.
Control is transferred to the next statement.

While Loop Program Example

public class WhileLoopExample {
    public static void main(String[] args) {
        // Input: Define the value of n
        int n = 5; // You can change this value to test with different inputs

        int sum = 0; // Initialize sum to 0
        int i = 1;   // Start from 1

        // While loop to calculate the sum of first n natural numbers
        while (i <= n) {
            sum += i; // Add i to sum
            i++;      // Increment i
        }

        // Output: Display the result
        System.out.println("The sum of the first " + n + " natural numbers is: " + sum);
    }
}

Explanation:

In this program, we directly assign a value of 5 to the variable n.
Two variables are initialized: sum (to accumulate the total sum) and i (to iterate through the numbers starting from 1).
While Loop: The loop continues as long as i is less than or equal to n. Inside the loop:
- The current value of i is added to sum.
- The value of i is incremented by 1.
After the loop completes, the program prints the calculated sum of the first n natural numbers.

Output

The sum of the first 5 natural numbers is: 15

Note : If you want to learn more about while loop in detail and programming examples with while loop, then click here

For loop

In a for loop, the initialization, test expression, and update expression are written in a single line. The for loop is commonly used for traversing arrays, including multi-dimensional arrays, and for generating pattern programs.

Syntax

for (initialization; condition; increment/decrement) 
{ 
// statement
}

Flowchart

Explanation:

A variable is initialized in the initialization expression.
The test condition is then checked.
If the condition is true, the loop body is executed.
After execution, the variable is updated, and the control moves back to the test condition.
The loop will continue running until the condition becomes false.
When the condition becomes false, the loop body is skipped, and control is transferred to the next statement in the program.

For loop Program Example

public class ForLoopExample {
    public static void main(String[] args) {
        // For loop to print numbers from 1 to 5
        for (int i = 1; i <= 5; i++) {
            System.out.println("Value of i: " + i);
        }
    }
}

Explanation:

The loop starts with i = 1.
The loop runs as long as i <= 5. Once i becomes greater than 5, the loop stops.
After each loop iteration, the value of i is incremented by 1 (i++).
The loop prints the value of i during each iteration.

Output

Value of i: 1
Value of i: 2
Value of i: 3
Value of i: 4
Value of i: 5

Note : If you want to learn more about for loop in detail and programming examples with for loop, then click here

Conclusion

In summary, the key difference between the for and while loops in Java is how they handle initialization, condition checking, and iteration. The for loop is best suited for scenarios where the number of iterations is known in advance, while the while loop is ideal when the condition is evaluated repeatedly until it becomes false. Both loops are essential for different use cases in programming.

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Difference Between For and While loop in java with Examples

While loop

Syntax:

Flowchart

Explanation:

While Loop Program Example

Explanation:

For loop

Syntax

Flowchart

Explanation:

For loop Program Example

Explanation:

Conclusion

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