Java-- judge palindrome

Package Basic; 

Import java.util.Scanner; 

public  class Palindrome {
     public  static  Boolean isPalindrome (String raw) { 
        String str = "" ;
         // take only the string of the letters in raw, in splicing to str 
        for ( int I = 0 ; I <raw.length (); I ++ ) {
             char CH = raw.charAt (I);
             IF ((CH> = 'A' && CH <= 'Z') || (CH> = 'A' && CH <= 'the Z' )) { 
                STR + = CH;
            } 
        } 
        // STR letter lowercase & 
        str = str.toLowerCase();
        // 判断是否为回文
        int end = str.length();
        for(int i = 0; i < end/2; i++){
            if(str.charAt(i) != str.charAt(end-i-1)){
                return false;
            }
        }

        return true;
    }

    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        // I prefer pi!
        // A man, a plan, a canal: Panama!
        // Madam, I am Adam.
        System.out.printf("Enter a message: ");
        String str = scanner.nextLine();

        if(isPalindrome(str)){
            System.out.println("Palindrome!");
        }else{
            System.out.println("Not a palindrome!");
        }
    }
}