For each loop in java program | Enhanced for loop in java program

For-each loop or also known as enhance for-loop is introduced in JDK 1.5. Just like for-loop while loop and do-while loop, a for-each loop is also a way of iterating objects in the java. If you want to know more about loop then, I have an article on loops in java

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The syntax for for-each loop in java

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 for(Object-type object-name : object)
  {
      // statement block
  }

Example of the for-each loop in java

 int[] numbers = {1,2,3}
  for (int number : numbers)
  {
      // statemnet blocks
  }

NOTE: for-each only work with the same data type. This means Object-type and objects both data type should be the same. Here int is the Object-type and numbers is an array but the data type of numbers is int. So, here we can use a for-each loop to iterate numbers.

In the above example, we have declared a single-dimensional array, which is numbers

numbers have 3 elements such as 1,2 and 3

Here the object-type is int

To iterate numbers using a for-each loop, we have used the syntax of for each loop which we have discussed early

How does for each-loop works?

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In java, the for-each loop will travel till the last elements of the Object(arrays or collection).

In an above simple example, we had declared one array which is number and this array have 3 elements, once we iterate this array for-each loop will travel three times because array (numbers) have 3 elements

Java Example of the for-each loop

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 public class ForEachLoop
  {
      public static void main(String[] args)
      {
          int[] numbers = { 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 };

          for(int number : numbers)
          {
              System.out.println("number = " + number);
          }

      }
  }

Output of the above program

number = 10
number = 20
number = 30
number = 40
number = 50
number = 60
number = 70
number = 80
number = 90
number = 100(code-box)

Explanation of the above program

As you can see in the program, we have created on the array which is number and values of the array is 10,20, 30, 40, 50, 60, 70, 80, 90 and 100

To iterate this array, we have used for each loop

As you know for-each loop start with for keyword and followed by parenthesis, inside parenthesis we assign one variable of the same data type which we wan to iterate

In this program, we are iterating array of int data type, so we create int variable inside for-each loop parenthesis

After declaring the int variable, we need to use colon (:)

After that use your object, here we have an array with numbers, so we have written numbers

Now, it looks like this for(int number : numbers)

Inside of for-each loop (statement block), we are printing all elements of numbers

Some drawback of the for-each loop in java

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The major disadvantage of the for-each loop is you can't access an element by using an index.

Drawback of for-each loop example

  int[] numbers = { 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 };
  for (int i=0; i<=9; i++)
  {
      if (i == 3 || i== 5)
      {
          System.out.println("number = " + numbers[i]);
      }
  }

In the above program, we are using for loop. In for-loop, we have control of the index of the object, so here are printing only those value whose index is equal to 3 and 5

In a for-each loop, we don't have control on indexes, because the for-each loop starts iterating from start to end

Java program to iterate List collection using for-each loop

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  public class ForEachList
  {
      public static void main(String[] args)
      {
          List numbers = Arrays.asList(1,2,3,4,5);

          for(Integer number : numbers)
          {
              System.out.println("number = " + number);
          }
      }
  }

Output of the above program

number = 1
number = 2
number = 3
number = 4
number = 5(code-box)

Let us have another example of List collection using a for-each loop, but this time we will use String instead of Integer

  public class ForEachList
  {
      public static void main(String[] args)
      {
          List message = Arrays.asList("learning", "java", "with", "learnjavaskills.in", "is", "fun");

          for(String singleElement : message)
          {
              System.out.print(singleElement + " ");
          }
      }
  }

Output of the above program

learning java with learnjavaskills.in is fun(code-box)

Conclusion

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Today we had learned a for-each loop in java, how to use a for-each loop in java, and also learned when not to use a for-each loop in java.

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