cinmay Xu

Yes， I tested the first two parts and they worked well. I need help from here :
// Go over each character of input
// If that single character is NOT a valid digit of that base, return false immediately
// If you finish going through the characters, return true
I don't know how to compare each char with the base.
Could you give me some tips?

Henry Wong wrote:
It is generally a good idea to write and test each piece -- as you are building your application. This means that you need to make sure it compiles, even though the program is not complete, so that you may test it... So...

cinmay Xu wrote:Need help on java coding homework: chose the base(X=2,3,4,5,6,7,8,9,10)),enter an 8 digit number and let the program to judge if the number is based x(2-10). I already wrote the first two parts and need help on the others.

Have you tested and confirm that the first two parts work? Does what you have compile?

Henry

Need help on java coding homework: chose the base(X=2,3,4,5,6,7,8,9,10)),enter an 8 digit number and let the program to judge if the number is based x(2-10). I already wrote the first two parts and need help on the others.

Don't know how to do these:

[Go over each character of input
If that single character is NOT a valid digit of that base, return false immediately
If you finish going through the characters, return true]

Next is the code:

import java.util.Scanner; public class BaseX { public static void main(String[] args){ Scanner scan = new Scanner(System.in); String input = ""; int base = 0; // Prompt the user to specify a base between 2 and // 10, and store that value in the variable "base" // Force the user to give a value in that range. do{ System.out.print("Specify your base (2-10): "); base = scan.nextInt(); }while(base<2 || base >10); System.out.println(); // So long as the String input is NOT 1-8 in length, // Ask the user to enter a valid base-X number up to 8 digits // Save the next line of user input to the variable "input" do{ System.out.print("Enter a valid base-" + base + " number up to 8 digits long:"); input = scan.next(); }while(input.length() != 8 ); // If the input string is NOT base-X, tell the user "Bad input!" // Otherwise, tell the user "You entered [numeric value of input]" // You can call the methods like so: // isBaseX(input, base) This will give you a true or false value // baseXValue(input, base) This will give you an int value if (isBaseX == true) //Don't know if these codes are right or not. System.out.println("You entered " + input); else System.out.println("Bad input!"); private static boolean isBaseX(String input, int base){ // Go over each character of input // If that single character is NOT a valid digit of that base, return false immediately // If you finish going through the characters, return true return true; } private static int baseXValue(String input, int base){ int result; // To start, the exponent is 0 and the next position in // in the input string is the string length minus one. // You already have an int variable to hold your result. // While the exponent is smaller than the string length, // Get the character at the next position in the input string // and store it in a char variable // Subtract '0' (not 0) from that character and multiply // the result of that subtraction by (int) Math.pow(base, exponent) // When the loop is finished, assign the result to the variable "result" return result; } }