Java for loop syntax: "for (T obj : objects)"

Question

I came across some Java syntax that I haven't seen before. I was wondering if someone could tell me what's going on here.

for (ObjectType objectName : collectionName.getObjects())

Solution 1

It's called a for-each or enhanced for statement. See the JLS §14.14.2.

It's syntactic sugar provided by the compiler for iterating over Iterables and arrays. The following are equivalent ways to iterate over a list:

List<Foo> foos = ...;
for (Foo foo : foos)
{
    foo.bar();
}

// equivalent to:
List<Foo> foos = ...;
for (Iterator<Foo> iter = foos.iterator(); iter.hasNext();)
{
    Foo foo = iter.next();
    foo.bar();
}

and these are two equivalent ways to iterate over an array:

int[] nums = ...;
for (int num : nums)
{
    System.out.println(num);
}

// equivalent to:
int[] nums = ...;
for (int i=0; i<nums.length; i++)
{
    int num = nums[i];
    System.out.println(num);
}

Further reading

• How is Java's for loop code generated by the compiler
• The For-Each Loop

Solution 2

The variable objectSummary holds the current object of type S3ObjectSummary returned from the objectListing.getObjectSummaries() and iterate over the collection.

Here is an example of this enhanced for loop from Java Tutorials

class EnhancedForDemo {
 public static void main(String[] args){
      int[] numbers = {1,2,3,4,5,6,7,8,9,10};
      for (int item : numbers) {
        System.out.println("Count is: " + item);
      }
 }
}

In this example, the variable item holds the current value from the numbers array.

Output is as follows:

Count is: 1
Count is: 2
Count is: 3
Count is: 4
Count is: 5
Count is: 6
Count is: 7
Count is: 8
Count is: 9
Count is: 10

Hope this helps !

Solution 3

yes... This is for each loop in java.

Generally this loop is become useful when you are retrieving data or object from the database.

Syntex :

for(Object obj : Collection obj)
{
     //Code enter code here
}

Example :

for(User user : userList)
{
     System.out.println("USer NAme :" + user.name);
   // etc etc
}

This is for each loop.

it will incremental by automatically. one by one from collection to USer object data has been filled. and working.

Solution 4

That's the for each loop syntax. It is looping through each object in the collection returned by objectListing.getObjectSummaries().

Solution 5

for each S3ObjecrSummary in objectListing.getObjectSummaries()

it's looping through each item in the collection

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