Java For and For-Each Loops

The for loop in Java is a control flow statement that iterates a part of the programs multiple times. It’s ideal for when you know in advance how many times you want to execute a block of code. Here, we’ll explore the for loop through various examples, explaining their use and function.

Basic for Loop

A basic for loop includes initialization, condition, and increment/decrement in a single line, making it concise and easy to understand.


Looping Through an Array

You can use a for loop to iterate through each element of an array.


Enhanced for Loop (For-Each)

Java provides the enhanced for loop, also known as the for-each loop, which simplifies iterating through arrays or collections.


Nested for Loops

You can use a for loop inside another for loop to iterate over two dimensions, which is particularly useful for matrices.


Infinite for Loop

An infinite loop runs forever unless the program is terminated. It can be created by leaving the condition empty.


for Loop with Multiple Variables

You can initialize and update multiple variables in a single for loop.


These examples illustrate the versatility of the for loop in Java, showing how it can be used for simple counting, iterating over arrays and collections, handling nested loops, and even managing multiple variables within a single loop. Understanding how to effectively use for loops enhances your ability to write concise and efficient Java code.

Using break in a For Loop

The break statement terminates the loop immediately when it’s executed. It’s useful when you need to stop the loop execution under certain conditions before it naturally concludes.

Example: Find the first number divisible by 7 in a range.

In this example, the loop searches for the first number divisible by 7 between 1 and 100. Once found, it prints the number and exits the loop using break.

Using continue in a For Loop

The continue statement skips the current iteration of the loop and proceeds to the next iteration. It’s used to skip over certain conditions within the loop.

Example: Print all numbers from 1 to 10 except those divisible by 3.

Here, the loop iterates from 1 to 10. The continue statement is used to skip printing numbers that are divisible by 3, resulting in only non-multiples of 3 being printed.

Combining break and continue

While break and continue serve different purposes, they can be used together within a loop to control its execution more granely.

Example: Exit the loop after printing the first 5 numbers, skipping any number that is divisible by 4.

In this combined example, the loop is controlled to print the first 5 numbers that are not divisible by 4 by using both continue to skip unwanted numbers and break to exit after meeting the desired count.

These examples illustrate the versatility of break and continue in controlling the execution flow of for loops in Java, enabling more complex and conditional iterations tailored to specific programming needs.

For-Each Loop

The “for-each” loop, also known as the enhanced for loop, was introduced in Java 5. It offers a simpler way to iterate through elements in arrays and collections without using an index variable. The for-each loop is particularly useful when you need to access each element in a collection or array sequentially without modifying the array’s contents.

Syntax of the For-Each Loop

The basic syntax of the for-each loop is as follows:

  • declaration: The newly declared block variable, of a type compatible with the elements of the array or collection being accessed.
  • expression: This must evaluate to an array or a Java Iterable object.

Examples of For-Each Loop

Iterating Over an Array

In this example, the for-each loop iterates over the colors array. The variable color is automatically set to each element in the array, one at a time, and printed out.

Iterating Over a Collection

Collections in Java, such as ArrayList, can also be iterated using the for-each loop.

This example shows how to iterate over a List of String objects. Each element in the list is accessed in order and printed.

Using For-Each with Multidimensional Arrays

While the for-each loop is straightforward for single-dimensional arrays, it requires a bit more work for multidimensional arrays since you need to use a nested for-each loop.

In this multidimensional array example, the outer for-each loop iterates over each row of the matrix, and the inner loop iterates over each element in the row.

Benefits of Using For-Each Loop

  • Clarity and Conciseness: The for-each loop is more readable, especially when the index is not needed within the loop body.
  • Reduces Errors: By eliminating the need for an index variable, it minimizes the risk of programming errors, such as off-by-one errors.
  • Enhanced for Collections: It abstracts the iterator, making the code cleaner and more straightforward when working with collections.

The for-each loop is a powerful feature for iterating over collections and arrays in Java, making code more readable and reducing the chance of errors. It is particularly useful in scenarios where you need to perform operations on each element of a collection or array but do not need to modify the underlying structure.

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