Initializing an Array in Java Using the 'Advanced' for Each Loop

Initializing an array in Java using the 'advanced' for each loop

No, because you aren't assigning to the array, you are assigning to the temporary variable called i. The array doesn't see the change.

The following shows roughly equivalent code using the normal for loop. This should make it easier to see why it fails to update the array:

for (int j = 0; j < numbers.length; j++) { 
    Integer i = arr[j]; // i is null here.
    i = counter++; // Assigns to i. Does not assign to the array.
}

How can I initialize an array with an enhanced for-loop?

If the array reference ('Wasberen' in this case) in an enhanced for statement is null, then a NullPointerException will result when the statement is executed.

Can you use array initialization in an enhanced for loop?

You can write:

for (int number : new int[] {one, two ,three}) {
    System.out.println(number);
}

You can also use List.of() if you are using Java 9 or above.

for (int number : List.of(one, two ,three)) {
    System.out.println(number);
}

Is it possible to initialise an array in the for each loop's condition area?

Well, you learn something new everyday. Apparently you can initialize an array but you must define the type and not just use an array initializer.

This works

        for (String string : new String[] { "a", "b", "c" }) {
            //code
        }

This doesn't work because it's unaware of type.

        for (String string : { "a", "b", "c" }) {
            //code
        }

for each loop cannot initialize objects in array

In your for-each example you are overwriting the local variable of the loop which does not get saved back into the array. It is similar to in your second loop going:

for(int i = 0; i < buffer.length; i++){
    Vector v = buffer[i];
    v = new Vector();
}

Check out Understanding for each loop in Java for basically the same issue.

Is it possible to initialize the objects in an array through an enhanced for loop?

No, this is not possible, because an enhanced for loop will give a reference to the current element. Assigning a new object to the reference won't assign the element to the array. There is no substitute for using an array access expression to assign an element to an array.

You can use two "traditional" for loops with an array access expression to initialize the array.

for (int s = 0; s < SUITS; s++)
   for (int c = 0; c < RANKS; c++)
       cards[s][c] = new Card(...);

It's possible to use an array initializer, but it would tedious, excessively verbose, and error-prone.

cards = new Card[][] {
  {new Card(...), new Card(...), ... },
  {new Card(...), new Card(...), ... },
  ...};

Interestingly, because the 2D array is implemented as an array of arrays, and array references are used, the outer array can be initialized with an enhanced for loop, as long as the inner array is initialized with a "traditional" loop. This works because suit is an array in cards, so suit[c] is an element in cards.

cards = new Card[SUITS][RANKS];

for(Card[] suit : cards) {
    for(int c = 0; c < RANKS; c++) {
        suit[c] = new Card(suitVar, rankVar);
    }
}

How to use foreach or enhanced for loop for multidimensional array in java?

Each element of your num array is an int array itself. If you want a for-each loop you will have to use int[] as a type for the loop variable.

class Kevil{
public static void main(String[] args){

int[][] num={{1,2,3,4,5,6,7,8,9,10},{11,12,13,14,15,16,17,18,19,20},{21,22,23,24,25,26,27,28,29,30}};

for(int[] i : num) {
    for(int j : i){
        System.out.print(j);
        System.out.print(" ");
    }
    System.out.print("\n");
}

}
}

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