Why do I get a blank output when I try to print ASCII table by array approach in Java?

Question

Writing a program to print the ASCII values of all 256 characters.

    int digit[] = new int[256];
    char array[] = new char[256];

    for(int i=0;i<array.length;i++)
    {
        array[i] = (char) digit[i];
    }
    for(int i=0;i<array.length;i++)
    {
        System.out.println(array[i]);
    }

I get a blank output when I run this code.

Replace array[i] = (char) digit[i] with array[i] = (char) i — Arvind Kumar Avinash
– Arvind Kumar Avinash, Commented Jun 24, 2020 at 23:06
Considering you're not initialising digit[] with any values before you read them into array[], why do you expect the output not to be blank? — Michael Berry
– Michael Berry, Commented Jun 24, 2020 at 23:06
Mr. Nitpicker writes: ASCII is a 7 bit code; codepoints > 127 are not ASCII. Also, this is Java, so a char is a 16-bit Unicode (specifically UTF-16) value. Codepoints 0-127 are identical to ASCII; beyond that, see Unicode. — user13784117
– user13784117, Commented Jun 24, 2020 at 23:23

Arvind Kumar Avinash · Accepted Answer · 2021-03-03 17:02:57Z

3

You do not need int digit[]. You only need to loop from 0 to 255 and cast each int to a char.

for (int i = 0; i < 256; i++) {
    array[i] = (char) i;
}

Alternatively, you can write a for loop using char.

for (char i = 0; i < 256; i++) {
    System.out.println(i);
}

edited Mar 3, 2021 at 17:02

Arvind Kumar Avinash

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answered Jun 24, 2020 at 23:08

Unmitigated

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Comments

Mureinik · Accepted Answer · 2020-06-24 23:08:34Z

0

Since you didn't initialize them, all the elements in digit are 0, and ASCII 0 is the null character.

TO be honest, you don't need an array there - just iterate over them numbers 0 to 255 and print their cast to chars:

for (int i = 0; i < 256; ++i) {
    System.out.println(i + " -- " + ((char)i)));
}

answered Jun 24, 2020 at 23:08

Mureinik

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2 Comments

Vaishakh Y Kumar Over a year ago

Thanks for the answer. Could you please tell how should I have initialized the array to get the desired output?

Mureinik Over a year ago

@VaishakhYKumar you could loop over digits and initialized it - for (int i = 0; i < 256; ++i) {digits[i] = i;}

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