老哥为何答案正确不了

Question

public class ExceptionTest {

public static void main(String[] args) {

Scanner sc=new Scanner(System.in);

try {

System.out.println("你的选择是:A,B,C,D");

String s=sc.next();

if(s=="a"){

System.out.println("选择正确");

}

else{

System.out.println("选择错误");

}

} catch (InputMismatchException e) {

System.out.println("请重新输入");

}

}

}