Day 07 - 12 Sep - Loop end

For Loop

In Java, a for loop is a control structure that allows you to execute a block of code repeatedly based on a specified condition. It's commonly used when you know in advance how many times you want to repeat a certain task. Let's break down the parts of a for loop:

for (initialization; condition; update) {
    // Code to be executed repeatedly
}

Here's what each part does:

1. Initialization: This is where you initialize a control variable (usually an integer) to a starting value. It's executed only once when the loop begins.

2. Condition: This is a boolean expression that's checked before each iteration of the loop. If the condition is true, the loop continues to execute. If it's false, the loop terminates.

3. Update: This part is responsible for changing the value of the control variable after each iteration. It's executed at the end of each iteration, just before re-checking the condition.

Now, let's look at an example:

public class WhileLoopExample {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Iteration " + i);
        } //for block
    } //main method block
} //class block

In this example:

• Initialization: int i = 1 initializes i to 1.

• Condition: i <= 5 checks if i is less than or equal to 5.

• Update: i++ increments i by 1 after each iteration.

The output of this loop will be:

Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5

The loop starts with i equal to 1. It prints "Iteration 1," increments i to 2, and so on until i becomes 6, at which point the condition becomes false, and the loop terminates.

You can use for loops for a wide range of tasks, such as iterating over arrays, processing data, or performing calculations. They provide precise control over the number of iterations, making them a valuable tool in Java programming.

While Loop

The while loop in Java is used to repeatedly execute a block of code as long as a specified condition is true. Here's the basic structure of a while loop:

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

Example Programs

Let's write a simple program that uses a while loop to print numbers from 1 to 5:

public class WhileLoopExample {
    public static void main(String[] args) {
        int i = 1;
        while (i <= 5) {
            System.out.println("Number: " + i);
            i++;
        } //while block
    } //main method block
} //class block

In this program:

• int i = 1 initializes i to 1.

• i <= 5 checks if i is less than or equal to 5.

• System.out.println("Number: " + i); prints the value of i.

• i++ increments i by 1 after each iteration.

This program will output:

Number:1
Number:2
Number:3
Number:4
Number:5

Foreach Loop

Lets learn about the "enhanced for loop" or "for-each loop" in Java. This loop is used for iterating over collections like arrays and lists without the need for indices. It's quite beginner-friendly and simplifies iteration. Here's the basic structure of a foreach loop:

for (datatype element:collection) {
    // Code to be executed for each element
}

• datatype: The type of elements in the collection.

• element: A variable to represent each element in the collection.

• collection: The array or collection you want to iterate over.

Example Programs

Let's say you have an array of integers and you want to print each element:

public class ForEachLoopExample {
    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5};
        for (int num : numbers) {
            System.out.println("Number: " + num);
        } //for each block
    } //main method block
} //class block

In this example:

• int num is used to represent each element in the numbers array.

• for (int num : numbers) iterates over each element in the array.

• System.out.println("Number: " + num) prints each element.

The for-each loop is efficient and simplifies the code when you need to iterate over elements in collections, making it a great choice for beginners.