Looping Statements in Java Programming Language

A loop in programming is a control structure that repeats a block of code multiple times.

Java provides three types of loops:

1. for loop
2. while loop
3. do-while loop

Each of these loops serves a different purpose and can be used depending on the specific requirement.

For loop in Java

The for loop is used when we know the exact number of times we need to repeat a block of code.

It is written in the following syntax:

for (initialization; condition; increment/decrement) {
  // code to be executed
}

• initialization: This is the starting point of the loop. It is executed only once before the loop starts.
• condition: This is the condition that must be true for the loop to continue executing.
• increment/decrement: This is used to update the value of the loop variable with each iteration.

Here’s an example program that demonstrates the use of for loop to print numbers from 1 to 5:

public class ForLoopExample {
  public static void main(String[] args) {
    for (int i = 1; i <= 5; i++) {
      System.out.println(i);
    }
  }
}

Output:

1
2
3
4
5

while loop

The while loop is used when we do not know the exact number of times we need to repeat a block of code.

It is written in the following syntax:

while (condition) {
  // code to be executed
}

• condition: This is the condition that must be true for the loop to continue executing.

Here’s an example program that demonstrates the use of 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(i);
      i++;
    }
  }
}

Output:

1
2
3
4
5

do-while loop in Java

The do-while loop is similar to the while loop, but it guarantees that the code inside the loop is executed at least once, even if the condition is false. It is written in the following syntax:

do {
  // code to be executed
} while (condition);

• condition: This is the condition that must be true for the loop to continue executing.

Here’s an example program that demonstrates the use of do-while loop to print numbers from 1 to 5:

public class DoWhileLoopExample {
  public static void main(String[] args) {
    int i = 1;
    do {
      System.out.println(i);
      i++;
    } while (i <= 5);
  }
}

Output:

1
2
3
4
5

These are the three types of loops in Java. Depending on the specific requirement, one of these loops can be used to repeat a block of code.

For-each loop in Java

The for-each loop, also known as the enhanced for loop, is a convenient way to iterate over collections, arrays, or any object that implements the Iterable interface.

It was introduced in Java 5 and is written in the following syntax:

for (datatype variable : collection) {
  // code to be executed
}

• datatype: This is the data type of the elements in the collection.
• variable: This is the name of the variable that will hold each element in the collection.
• collection: This is the collection over which we want to iterate.

Here’s an example program that demonstrates the use of a for-each loop to iterate over an array of strings:

public class ForEachLoopExample {
  public static void main(String[] args) {
    String[] fruits = {"apple", "banana", "orange", "mango", "grape"};

    for (String fruit : fruits) {
      System.out.println(fruit);
    }
  }
}

Output:

apple
banana
orange
mango
grape

In this example, we have an array of strings named fruits. We use the for-each loop to iterate over each element of the array and print it to the console.

The for-each loop is especially useful when we need to iterate over collections that do not have a fixed size or when we do not need to modify the collection during iteration. It makes the code more readable and less error-prone.

Note that the for-each loop can only be used to iterate over collections that implement the Iterable interface or arrays. If we need to iterate over other types of collections, we can use the Iterator interface or the ListIterator interface.

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