配列の後にcharAt()が使えない

Question

前提・実現したいこと

現在、九桁のString型の数字を九回入力しそれを一文ずつ配列に収納して、表示しようとしています。ですが、収納しようとするときにエラーが出てしまい配列に追加できません。
直し方を教えてください。

発生している問題・エラーメッセージ

test02.java:19: エラー: 不適合な型: charをStringに変換できません:
                                answers[i] = boards[ti].charAt(i);
                                                              ^
エラー1個

該当のソースコード

import java.util.Scanner;
public class test02
{
	static int loop=0;
	static String answers[] ={"0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0"};
	static String boards[] ={"0","0","0","0","0","0","0","0","0"};
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
		System.out.println("九桁の数字を入力してください。");
		for(int i=0;i<9;i++){
			int dan=i+1;
			System.out.print(">"+dan+">");
			boards[i] = sc.next();
		}
		int end=0;
		for(int ti=0;end==1;ti++){
			for(int i=0;i<9;i++){
				answers[i] = boards[ti].charAt(i);
			}
		}
		
		for(String answer:answers){
			System.out.print(answer+" ");
			loop++;
			if(loop==9){
				System.out.println();
				loop=0;
			}
		}
	}
}

補足情報（FW/ツールのバージョンなど）

java jdk-14.0.2

Answer 1

直し方を知るためには、まず原因を知る必要があります。
Javaにおいて、文字型の値と長さ1の文字列型の値は全くの別物です。

char   ch1 = 'a';   // ok
String ch2 = "a";   // ok
char   ch3 = "a";   // ng
String ch4 = 'a';   // ng

今回のエラーはまさにこれに起因します。
String#charAtの戻り値はchar型です。String型ではありません。

---

char型の文字を長さ1のStringにしたい場合、String.valueOfが便利です。

String str = String.valueOf('a');   // ok