For-each loop in Java

Prerequisite: Decision making in Java

For-each is another array traversing technique like for loop, while loop, do-while loop introduced in Java5.

• It starts with the keyword for like a normal for-loop.
• Instead of declaring and initializing a loop counter variable, you declare a variable that is the same type as the base type of the array, followed by a colon, which is then followed by the array name.
• In the loop body, you can use the loop variable you created rather than using an indexed array element.
• It’s commonly used to iterate over an array or a Collections class (eg, ArrayList)

Syntax:

for (type var : array) 
{ 
    statements using var;
}

is equivalent to:

for (int i=0; i<arr.length; i++) 
{ 
    type var = arr[i];
    statements using var;
}

// Java program to illustrate 
// for-each loop
class For_Each     
{
    public static void main(String[] arg)
    {
        {
            int[] marks = { 125, 132, 95, 116, 110 };
            
            int highest_marks = maximum(marks);
            System.out.println("The highest score is " + highest_marks);
        }
    }
    public static int maximum(int[] numbers)
    { 
        int maxSoFar = numbers[0];
        
        // for each loop
        for (int num : numbers) 
        {
            if (num > maxSoFar)
            {
                maxSoFar = num;
            }
        }
    return maxSoFar;
    }
}

Output:

The highest score is 132

Limitations of for-each loop

1. For-each loops are not appropriate when you want to modify the array:

   for (int num : marks) 
   {
       // only changes num, not the array element
       num = num*2; 
   }
   

2. For-each loops do not keep track of index. So we can not obtain array index using For-Each loop

   for (int num : numbers) 
   { 
       if (num == target) 
       {
           return ???;   // do not know the index of num
       }
   }
   

3. For-each only iterates forward over the array in single steps

   // cannot be converted to a for-each loop
   for (int i=numbers.length-1; i>0; i--) 
   {
         System.out.println(numbers[i]);
   }
   

4. For-each cannot process two decision making statements at once

   // cannot be easily converted to a for-each loop 
   for (int i=0; i<numbers.length; i++) 
   {
       if (numbers[i] == arr[i]) 
       { ...
       } 
   }
   

Related Articles:
For-each in C++ vs Java
Iterator vs For-each in Java

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