For-each Loop in Java with Example: Simple Guide for Beginners

Introduction

Java is one of the most popular programming languages in the world. One of its strengths is the variety of loop constructs it provides to iterate over data structures. Among them, the for-each loop (also known as the enhanced for loop) is a concise and readable alternative to the traditional for loop, especially when dealing with arrays or collections. In this article, we’ll explore everything you need to know about the for-each loop in Java, including syntax, use cases, limitations, and practical examples.

What is a For-each Loop?

The for-each loop is a control flow statement introduced in Java 5 (JDK 1.5) to simplify the process of iterating over arrays and collections. It removes the need for using an index or iterator, thereby reducing boilerplate code.

Syntax of the For-each Loop

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for (datatype variable : arrayOrCollection) {

// body of loop

}

Example:

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int[] numbers = {1, 2, 3, 4, 5};

for (int number : numbers) {

System.out.println(number);

}

Key Differences Between Traditional and For-each Loop

Aspect	Traditional For Loop	For-each Loop
Index control	Explicit	Implicit
Suitable for	Arrays and indexed structures	Arrays and all Collections
Readability	Less (in complex cases)	More readable
Modifying contents	Possible	Not possible directly
Index access	Yes	No

Advantages of For-each Loop

Improved Readability: Clear and easy to understand.
Fewer Errors: No need to manage indices.
Compact Syntax: Cleaner and more concise.

Works with all Collections: Lists, Sets, and other Iterable types.

Use Cases of For-each Loop

Traversing arrays
Iterating over Java Collections
Looping through Lists, Sets, and Enums
Read-only operations over data structures

For-each with Arrays

Example:

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String[] names = {"Alice", "Bob", "Charlie"};

for (String name : names) {

System.out.println(names);

}

Output:

Alice

Bob

Charlie

For-each with Multi-dimensional Arrays

For-each loop can also be used for 2D arrays by nesting loops.

Example:

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int[][] matrix = {

{1, 2},

{3, 4}

};

for (int[] row : matrix) {

for (int value : row) {

System.out.print(value + " ");

}

System.out.println();

}

Output:

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1 2

3 4

For-each with Collections

Java Collections like List, Set, and Map support enhanced for loops since they implement the Iterable interface.

For-each with List

Example:

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import java.util.List;

import java.util.ArrayList;

List<String> cities = new ArrayList<>();

cities.add("New York");

cities.add("London");

cities.add("Tokyo");

for (String city : cities) {

System.out.println(city);

}

For-each with Set

Example:

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import java.util.HashSet;

import java.util.Set;

Set<Integer> numbers = new HashSet<>();

numbers.add(10);

numbers.add(20);

numbers.add(30);

for (int num : numbers) {

System.out.println(num);

For-each with Map (using keySet and entrySet)

Maps don’t directly support for-each, but their views do.

Using keySet():

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import java.util.Map;

import java.util.HashMap;

Map<String, Integer> map = new HashMap<>();

map.put("Apple", 2);

map.put("Banana", 3);

for (String key : map.keySet()) {

System.out.println(key + ": " + map.get(key));

}

Using entrySet():

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for (Map.Entry<String, Integer> entry : map.entrySet()) {

System.out.println(entry.getKey() + ": " + entry.getValue());

}

Using For-each Loop with Enums

Example:

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enum Day {

MONDAY, TUESDAY, WEDNESDAY

}

for (Day d : Day.values()) {

System.out.println(d);

}

Nested For-each Loops

For nested data structures, nested for-each loops are quite useful.

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List<List<Integer>> numberGrid = Arrays.asList(

Arrays.asList(1, 2),

Arrays.asList(3, 4)

);

for (List<Integer> row : numberGrid) {

for (int num : row) {

System.out.print(num + " ");

}

Modifying Elements During Iteration

The for-each loop doesn’t allow modifying the original structure directly. You must use indices or iterators for modifications.

Incorrect:

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for (int num : numbers) {

num *= 2; // Doesn't change the actual list

}

Correct:

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for (int i = 0; i < numbers.size(); i++) {

numbers.set(i, numbers.get(i) * 2);

}

Common Mistakes in For-each Loop

Trying to modify collection elements directly
Using with data structures that change size
Assuming access to index
Using with non-iterable objects

Performance Considerations

Slightly better performance than traditional loops for read-only access.
Doesn’t support parallelism or skipping elements.
Not suitable when index control is needed.

Using For-each Loop with Wrapper Classes

Java's auto-boxing allows for-each to work seamlessly with wrapper classes.

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Integer[] nums = {10, 20, 30};

for (Integer n : nums) {

System.out.println(n);

}

For-each with Generics

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List<Double> prices = new ArrayList<>();

prices.add(1.99);

prices.add(3.49);

for (Double price : prices) {

System.out.println(price);

}

Java 8 and Lambda with For-each

From Java 8, forEach method in collections works with lambdas.

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cities.forEach(city -> System.out.println(city));

Comparison with Stream API

Feature	For-each Loop	Stream API
Syntax	Simple	More flexible but verbose
Performance	Fast for small tasks	Good for complex tasks
Parallelism	Manual	Built-in support

For-each Loop in Real-world Applications

Logging records
Displaying UI elements from list
Reading configurations
Processing JSON or XML arrays

When Not to Use For-each Loop

When modifying the collection
When you need element index
When using backward iteration
When working with non-iterable types

Alternatives to For-each Loop

Traditional for loop
Iterator and ListIterator
Stream and Lambda
while and do-while loops

FAQs on For-each Loop in Java

Q1. Can I use a for-each loop with a Map?

Yes, by using entrySet() or keySet().

Q2. Can I remove elements using for-each loop?

No, it throws ConcurrentModificationException.

Q3. Is for-each faster than for loop?

For simple iterations, yes. But traditional loops are more flexible.

Summary and Conclusion

The Java for-each loop is a powerful and elegant tool for iterating over arrays and collections. Its main strength lies in its simplicity and readability. However, it comes with limitations, especially when modifications or index-based access is required. Understanding when and how to use the for-each loop effectively is key to writing clean, efficient, and maintainable Java code.

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