CODEWITHSUNDEEP
javaarraysfor-loop
Manish Joshi
Manish Joshi

Reputation: 95

Enhanced for loop for Strings

I am a beginner to coding. Currently I am learning arrays.

In the following code, I am trying to display the words entered by the user using a String array. The code is displaying null when using enhanced for-loop. Can anyone explain the problem?

The code is working fine with normal for-loop.

public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);

    String word;
    int count = 0;

    String[] words = new String[100];

    System.out.println("Enter the words (enter 'done' when finished):");

    do {
        System.out.println("Enter word "+ (count+1));
        word=scanner.nextLine();

        if (!word.equalsIgnoreCase("done")) {
            words[count]=word;
            count++;
        }
    }while (!word.equalsIgnoreCase("done"));

    System.out.println("Words entered are:");

    for (String print:words){
        System.out.println(print);
    }

    scanner.close();
}

The code should display the words entered by the user but it is displaying null instead of the word.

Upvotes: 4

Views: 10278

Answers (3)

Nicholas K
Nicholas K

Reputation: 15443

If you look closely it does print the words entered by the user. You are seeing null because the size of your array is 100. 

String[] words = new String[100];

Scroll up in your console to see the names originally entered by the user. You see nulls because the remaining elements in the array are null. For eg: if the user enters 5 words the remaining 95 words in the array are null.

You can add a null check to print out only the non-null values.

for (String print : words) {
    if (print != null) {
        System.out.println(print);
    }
}

If you are using java-8, you could just do :

Arrays.stream(words).filter(Objects::nonNull).forEach(System.out::println);

Upvotes: 1

Eran
Eran

Reputation: 393986

The enhanced for loop is not suitable in this case, since it is printing all 100 elements of the array, most of which are probably null.

When you use the regular for loop, you take advantage of the count variable, which lets you print only the initialized elements of the array:

for (int i = 0; i < count; i++) {
    System.out.println(words[i]);
}

If you insist on using the enhanced for loop, you can check for null elements, and break from the loop when you encounter the first:

for (String print:words){
    if (print != null) {
        System.out.println(print);
    } else {
        break; // once you encountered the first null, there's no point to continue the loop
    }
}

Upvotes: 4

Dawood ibn Kareem
Dawood ibn Kareem

Reputation: 79876

You've made an array with 100 entries. Initially, all 100 of them are null. Then, your do/while loop fills in a few of them. How many depends on the user, of course.

But then, you're printing all 100 entries of the array. You'll see a few words, then lots of nulls. You might be better to print only the entries that aren't null, like this.

for (String print:words){
    if (print != null) {
        System.out.println(print);
    }
}

Upvotes: 2

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