我正在尝试用java制作一个字母gusser，但是我的while循环不起作用。我得到的错误是
错误：二进制运算符“！=”的操作数类型错误while（输入！=ranletter）{^第一种类型：string第二种类型：char 1错误。
我试图将ranletter转换为char，但循环从未停止。
这是我的密码：

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int ranNum = (int)(Math.random()*26 + 97);
    char ranLetter = (char)ranNum;
    //This is just for testing
    System.out.println(ranLetter);

    String input = in.nextLine();
    if (input == String.valueOf(ranLetter)){
      System.out.println("FIRST TRY BTW!! the letter was " + ranLetter + ".");
    }

    else{
      int counter = 0;
      while (input != ranLetter){
        System.out.println("Nope :( try again.");
        counter += 1;
        input = in.nextLine();
      }
      System.out.println("Nice you got it. The letter was " + ranLetter + ". It took you " + String.valueOf(counter) + " guesses.");
    }
  }
}