Add alphabets to List Java [duplicate]

问题

This question already has answers here:

Better way to generate array of all letters in the alphabet (16 answers)

Closed last month.

I want create a list with alphabets with each alphabets for 5 times. I tried a code and it worked,

public class AlphabetsTest {
    public static void main(String[] args) {
        List<Character> alphabetList = new ArrayList<>();
        for (int i=0; i<3; i++){
            char chr='a';
            if (i==1)
                chr = 'b';
            if (i==2)
                chr = 'c';
            for (int j=0; j<5; j++){
                alphabetList.add(chr);
            }
        }
    }
}

But I would have to add multiple if conditions for more alphabets. Is there any better way to avoid it.

回答1:

You can use char loop as below,

List<Character> alphabetList = new ArrayList<>();
    for(char chr = 'a'; chr <= 'c'; chr++){
        for (int j=0; j<5; j++){
            alphabetList.add(chr);
    }
}

You may also want to use, Collections.nCopies to avoid inner loop,

for(char chr = 'a'; chr <= 'c'; chr++){
    alphabetList.addAll(Collections.nCopies(5, chr));
}

来源：https://stackoverflow.com/questions/61027316/add-alphabets-to-list-java