Mono_Cipher in java

import java.util.*;

public class Mono_Cipher{
    static String plain_txt,cipher_txt,crypt_txt;
public char[] key={'c','x','r','u','y','i','o','p','q','w','e','a','s','d','f','g','h','j','k','l','z','v','b','n','m','t'};

public void mono_encrypt(){
Scanner sc=new Scanner(System.in);
System.out.println("Enter Your Text");
plain_txt=sc.nextLine();

cipher_txt="";
int l=plain_txt.length();

for(int i=0;i<l;i++){
int tempAscii=(int)plain_txt.charAt(i);

if(tempAscii>96  && tempAscii<123){
tempAscii-=97;
}
cipher_txt+=key[tempAscii];

crypt_txt=cipher_txt;
}
System.out.println("Crypt text is"+"  "+crypt_txt);
}

public static void main(String args[]){
Mono_Cipher m=new Mono_Cipher();

m.mono_encrypt();
}
}