java转换字符

/*译密码。输入一个小写英文字符，将其转换为其后的第3个字符。*/
import java.util.Scanner;

public class TranslateChar {
	public static void main(String[] args) {		 
        Scanner sc=new Scanner(System.in);
        String ch1=sc.nextLine();
        char y=ch1.charAt(0);
        int y1=y-'0';
        int sum=3;
        if(y+3<='z'){
            char ch2=(char)(y+sum);
		    System.out.println(ch2);
        }
        else{
            char ch2=(char)(y-23);
            System.out.println(ch2);
        }
        
	}
}