How would you convert this method into a ternary expression?

I want to convert those if-statements into a ternary operator expression, but I’ve been struggling since I haven’t had the need to use them that much. The code essentially replaces the characters ‘1’ with ‘i’, removes characters that are not letters, and also removes upper-case letters by enqueuing elements that don’t meet those conditions.

private static Iterable<Character> transformationA(Queue<Character> q) {
    Queue<Character> retq = new Queue<>();
    for(Character c: q) {
        if(c.equals('1')) {
            retq.enqueue('i');
        }
        if(Character.isLowerCase(c)) {
            retq.enqueue(c);
        }
    }
    return retq;
}

Edit: thanks for your comments, code and suggestions.

Answer

Ternary operation does not fit

As commented, a ternary operation is not appropriate to your code. A ternary operation in Java is an expression, returning a result.

In your case, you do not have a “if x is true, return y, otherwise return z” situation. In your case you may enqueue an I, or you may enqueue a lowercase letter, or you may do nothing (thereby ignoring that nth character).

Unicode code points

The char type (and its Character wrapper class) are legacy, essentially broken. As a 16-bit value, the char type is incapable of representing even half of the characters defined in Unicode.

Instead use Unicode code point integer numbers.

• Pass in a collection of int or Integer (or IntStream) rather than Character objects. And actually, I would just pass in a CharSequence (the interface for String, etc.).
• To see if the code point represents the character for the digit 1, check for a code point number of 49 (decimal), the ASCII/Unicode number for the digit 1: if( codePoint == 49 ) { … } where codePoint is an int/Integer.
• For lowercase check, pass the code point integer: if( Character.isLowerCase( codePoint ) ) { … }.