Filling a Character Array With Characters from a String

How to fill a char array in C

Like this, probably

size_t prevlen = strlen(tval);
memset(tval + prevlen, ' ', 19 - prevlen);
*(tval + 19) = '\0';

Filling a character array with characters from a string

using ToCharArray() strings can be converted into character arrays.

Console.WriteLine("Enter a string: ");
var name = Console.ReadLine();

var intoarray= name.ToCharArray();

foreach (var n in intoarray)
    Console.WriteLine(n);

if you are using foreach, you should wait for the index to behave as if you were taking the value.

Console.WriteLine(n);

how to fill a char array with a given string

char[] mSeqA=parts[0].toCharArray();
char[] mSeqB=parts[1].toCharArray();

Filling a character array with subsequent letters in a string

Just put the chars to the array in a loop. You can use the original string's length to put in the fitting char using charAt(i % a.length()).

String a = "Example";
char[] b = new char[10];
for (int i = 0; i < b.length; i++) {
    b[i] = a.charAt(i % a.length());
}
for (char x : b) System.out.println(x);

Is there a way to fill string with characters at some specific indices?

You can't use String in the way you suggest, because String is immutable.

Another option, instead of StringBuilder, is to use a raw array of char. You know that the resultant string will have the same length as the source string, so you can do it like this:

1. Create an array using String.toCharArray.
2. Iterate from both ends simultaneously using indices i and j. Start index i from 0 moving forwards, and j from array length - 1, moving backwards.
3. Check the elements at i and j for a letter using Character.isLetter. If it's not a letter, just skip it by advancing i forwards or j backwards.
4. Swap the array elements at i and j.
5. Repeat while i < j.
6. Create the new string using new String(charArray)

As this looks like an exercise, I'll leave the actual coding to you.

Caveat: the above only works for strings where the Unicode code points are in the Basic Multilingual Plane (i.e. most strings to you and me). It won't work for tricky situations containing certain characters such as smileys (for more info on this potential problem, see https://dzone.com/articles/the-right-way-to-reverse-a-string-in-java).

fill array with character in string

You're assigning a character to a position in a String array. In your code, arr[i] refers to a String, and s.charAt(x) is a char.

It seems like arr should be a char array instead of a String array.

how to fill a char array with DIFFRENT chars in java?

The Answer by YourHelper seems correct.

Avoid char

Unfortunately, even the fixed version of your code will fail with most characters. The char type is essentially broken since Java 2, and legacy since Java 5.

To see char break, use a character like “”.

Code point

Use code point integers instead.

StringBuilder as result

Something like this untested code.

int limit = 5 ;
StringBuilder sb = new StringBuilder() ;

Scanner sc = new Scanner(System.in);

String input;
int codePoint;

for ( int i = 0 ; i < limit ; i++ ) {
    input = sc.next();
    int[] codePoints = input.codePoints().toArray() ;
    if ( codePoints.length == 1 ) {
        codePoint = codePoints[ 0 ] ;
        System.out.println( "for position " + i + " the input character is: " + Character.toString( codePoint ) );
        sb.appendCodePoint( codePoint );
        System.out.println("so we get the current result " + sb.toString() );
    } else {
        System.out.println( "Done: " + sb.toString() ) ;
        break;
    }
}
System.out.println( "Done: " + sb.toString() ) ;

See this code run live at IdeOne.com.

for index 0 the input character is: H
so we get the current result H
for index 1 the input character is: br>so we get the current result Hbr>for index 2 the input character is: l
so we get the current result Hl
for index 3 the input character is: l
so we get the current result Hll
for index 4 the input character is: o
so we get the current result Hllo
Done: Hllo

List of strings (characters) as result

If you want to collect each character individually, make a list of strings. Make a string of each code point, and add to list. Omit the StringBuilder.

List< String > characters = new ArrayList <>() ;
…
characters.add( Character.toString( codePoint ) ) ;

See an example of this code run live at IdeOne.com.

for index 0 the input character is: H
so we get the current result [H]
for index 1 the input character is: br>so we get the current result [H, ]
for index 2 the input character is: l
so we get the current result [H, , l]
for index 3 the input character is: l
so we get the current result [H, , l, l]
for index 4 the input character is: o
so we get the current result [H, , l, l, o]
Done: [H, , l, l, o]

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Be aware that in some languages what you may perceive as one "letter" is actually a combination of two characters, a letter followed by a "combining diacritical". Example here. Discussion here.

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