what is for-each loop in java

In detail, how does the 'for each' loop work in Java?

stackoverflow.com › questions › 85190 › in-detail-how-does-the-for-each-loop-work-in-java

for (Iterator<String> i = someIterable.iterator(); i.hasNext();) {
    String item = i.next();
    System.out.println(item);
}

Note that if you need to use i.remove(); in your loop, or access the actual iterator in some way, you cannot use the for ( : ) idiom, since the actual iterator is merely inferred.

As was noted by Denis Bueno, this code works for any object that implements the Iterable interface.

If the right-hand side of the for (:) idiom is an array rather than an Iterable object, the internal code uses an int index counter and checks against array.length instead. See the Java Language Specification.

for (int i = 0; i < someArray.length; i++) {
    String item = someArray[i];
    System.out.println(item);
}

Answer from nsayer on Stack Overflow

W3Schools

w3schools.com › java › java_foreach_loop.asp

Java For-Each Loop

Java Examples Java Videos Java ... ... There is also a "for-each" loop, which is used exclusively to loop through elements in an array (or other data structures):...

Stack Overflow

stackoverflow.com › questions › 85190 › in-detail-how-does-the-for-each-loop-work-in-java

foreach - In detail, how does the 'for each' loop work in Java? - Stack Overflow

Top answer

1 of 16

1310

for (Iterator<String> i = someIterable.iterator(); i.hasNext();) {
    String item = i.next();
    System.out.println(item);
}

Note that if you need to use i.remove(); in your loop, or access the actual iterator in some way, you cannot use the for ( : ) idiom, since the actual iterator is merely inferred.

As was noted by Denis Bueno, this code works for any object that implements the Iterable interface.

for (int i = 0; i < someArray.length; i++) {
    String item = someArray[i];
    System.out.println(item);
}

2 of 16

559

The construct for each is also valid for arrays. e.g.

String[] fruits = new String[] { "Orange", "Apple", "Pear", "Strawberry" };

for (String fruit : fruits) {
    // fruit is an element of the `fruits` array.
}

which is essentially equivalent of

for (int i = 0; i < fruits.length; i++) {
    String fruit = fruits[i];
    // fruit is an element of the `fruits` array.
}

So, overall summary:
[nsayer] The following is the longer form of what is happening:

for(Iterator<String> i = someList.iterator(); i.hasNext(); ) {
  String item = i.next();
  System.out.println(item);
}
Note that if you need to use i.remove(); in your loop, or access the actual iterator in some way, you cannot use the for( : ) idiom, since the actual Iterator is merely inferred.

[Denis Bueno]

It's implied by nsayer's answer, but it's worth noting that the OP's for(..) syntax will work when "someList" is anything that implements java.lang.Iterable -- it doesn't have to be a list, or some collection from java.util. Even your own types, therefore, can be used with this syntax.

Discussions

What is difference between for and foreach, and which is better?

foreach is used for iterating over anything that implements IEnumerable - Lists, arrays, collections, etc. It performs the action once for each element and gives you a reference to the current item. for is a general purpose loop that uses an initialiser, iterator and condition for control. It doesn't need a list object. for (initializer; condition; iterator) Which one is better to use depends on your use case. If you want to perform an action for every element in an IEnumerable, use foreach. For example, I want to give each of my employees a 10% raise: foreach (var emplyee in myCompany.Employees) { employee.Salary += employee.Salary / 10; } Use for when you want to do something a set number of times, or need complex control over the flow, such as making numbers count backwards, do something for ever odd number, etc. for (int i = 0; i < 100; i++) { // Count from 0 to 99 } for (int j = 100; j > 0; j--) { // Count from 100 to 1 } for (int k = 0; k < 100; k += 5) { // Count from 0 to 100 in steps of 5 } More on reddit.com

r/csharp

September 13, 2019

How does foreach Loop work in arraylist since the 'i' in for each loop is primitive

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r/javahelp

October 29, 2021

forEach loop not found in java?

String.split returns an array and not a collection Only collections have the .forEach method. You can wrap the array with Arrays.asList to get a list where you can call .forEach on. //Edit or can put the arrays value directly into a Stream. Streams have the forEach method as well. Arrays.stream(..) More on reddit.com

r/learnjava

October 16, 2020

Difference between for and for each?

The 'enhanced-for' is just 'syntax-sugar' for a for-loop (using a counter for arrays and an iterator for Iterables) Given `int[] numbers = {10, 20 ,30}; This... for (int value : numbers) { System.out.println(value); } is the same as... { int[] array = numbers; for (int len = array.length, i = 0; i < len; i++) { int value = array[i]; System.out.println(value); } } And given List strings = List.of("A", "B", "C") This... for (String value : strings) { System.out.println(value); } is the same as... for (Iterator i = strings.iterator(); i.hasNext(); ) { String value = i.next(); System.out.println(value); } Note that, in... for (int value : numbers) { System.out.println(value); } value is the value contained in the array, not an index used to access a value in the array. Your loop, using the enhanced-for, would need to keep a separate index variable. int[] ans = new int[nums.length * 2]; int i = 0; for (int value : nums) { ans[i] = value; ans[i + nums.length] = value; i++; } Or... If you want to be absolutely sure not to be hired in an interview... int[] ans = new int[nums.length * 2]; for (int value : nums) ans[ans[ans.length - 1]] = ans[nums.length + ans[ans.length - 1]++] = value; Edit: Fixed a code-typo More on reddit.com

r/learnjava

March 22, 2022

Videos

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What is For Each Loop Java | Java For Each Loop Syntax ...