问带有货币转换器java程序的字符串索引边界

EN

c= Keyboard.nextInt();

a = Keyboard.nextLine();

    // Your code before this while
} while (c != 0);

Keyboard.nextLine();  // Add this line before the next line

System.out.print("\nWould you like a summary of your conversions? (Y/N): ");
a = Keyboard.nextLine();

try {
    c = Integer.parseInt(Keyboard.nextLine());
} catch (NumberFormatException e) {
    e.printStackTrace();
}

package krc.utilz.io;

import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;


/**
 * A static library of helper methods to read keyboard input.
 * <p>
 * <strong>usage:</strong>
 * <code>
 *   import krc.utilz.io.Console;
 *   while ( (score=Console.readInteger("Enter an integer between 0 and 100 (enter to exit) : ", 0, 100, -1)) != -1) { ... }
 * </code>
 */
public abstract class Console
{
  private static final java.io.Console theConsole = System.console();
  static {
    if ( theConsole == null ) {
      System.err.println("krc.utilz.io.Console: No system console!");
      System.exit(2); // 2 traditionally means "system error" on unix.
    }
  }
  private static final DateFormat dateFormatter = new SimpleDateFormat("dd/MM/yyyy");
  private static final DateFormat timeFormatter = new SimpleDateFormat("HH:mm:ss");

  public static String readString(String prompt) {
    String response = readLine(prompt);
    if(response==null) throw new NullPointerException("response cannot be null");
    return response;
  }

  public static String readLine(String prompt) {
    if (!prompt.endsWith(" ")) prompt += " ";
    System.out.print(prompt);
    return theConsole.readLine();
  }

  public static String readString(String prompt, String regex) {
    while(true) {
      String response = readString(prompt);
      if ( response.length() > 0 ) {
        if ( response.matches(regex) ) {
          return response;
        }
      }
      System.out.println("Oops: A match for "+regex+" is required!");
    }
  }


  public static Date readDate(String prompt) {
    while(true) {
      try {
        return dateFormatter.parse(readString(prompt+" (dd/MM/yyyy) : "));
      } catch (java.text.ParseException e) {
        System.out.println("Oops: "+e);
      }
    }
  }

  public static Date readTime(String prompt) {
    while(true) {
      try {
        String response = readWord(prompt+" (HH:mm:ss) : ");
        return timeFormatter.parse(response);
      } catch (java.text.ParseException e) {
        System.out.println("Oops: "+e);
      }
    }
  }

  public static String readWord(String prompt) {
    while(true) {
      String response = readString(prompt);
      if(response.length()>0 && response.indexOf(' ')<0) return response;
      System.out.println("Oops: A single word is required. No spaces.");
    }
  }

  public static String readWordOrNull(String prompt) {
    while(true) {
      String response = readLine(prompt);
      if(response==null||response.length()==0) return null;
      if(response.indexOf(' ')<0 ) return response;
      System.out.println("Oops: A single word is required. No spaces.");
    }
  }

  public static char readChar(String prompt) {
    while ( true ) {
      String response = readString(prompt);
      if ( response.trim().length() == 1 ) {
        return response.trim().charAt(0);
      }
      System.out.println("Oops: A single non-whitespace character is required!");
    }
  }

  public static char readLetter(String prompt) {
    while(true) {
      String response = readString(prompt);
      if ( response.trim().length() == 1 ) {
        char result = response.trim().charAt(0);
        if(Character.isLetter(result)) return result;
      }
      System.out.println("Oops: A single letter is required!");
    }
  }

  public static char readDigit(String prompt) {
    while(true) {
      String response = readString(prompt);
      if ( response.trim().length() == 1 ) {
        char result = response.trim().charAt(0);
        if(Character.isDigit(result)) return result;
      }
      System.out.println("Oops: A single digit is required!");
    }
  }

  public static int readInteger(String prompt) {
    String response = null;
    while(true) {
      try {
        response = readString(prompt);
        if ( response.length()>0 ) {
          return Integer.parseInt(response);
        }
        System.out.println("An integer is required.");
      } catch (NumberFormatException e) {
        System.out.println("Oops \""+response+"\" cannot be interpreted as 32-bit signed integer!");
      }
    }
  }

  public static int readInteger(String prompt, int lowerBound, int upperBound) {
    int result = 0;
    while(true) {
      result = readInteger(prompt);
      if ( result>=lowerBound && result<=upperBound ) break;
      System.out.println("An integer between "+lowerBound+" and "+upperBound+" (inclusive) is required.");
    }
    return(result);
  }

  public static int readInteger(String prompt, int defaultValue) {
    String response = null;
    while(true) {
      try {
        response = readString(prompt);
        return response.trim().length()>0 ? Integer.parseInt(response) : defaultValue;
      } catch (NumberFormatException e) {
        System.out.println("Oops \""+response+"\" cannot be interpreted as 32-bit signed integer!");
      }
    }
  }

  public static int readInteger(String prompt, int lowerBound, int upperBound, int defaultValue) {
    int result = 0;
    while(true) {
      result = readInteger(prompt, defaultValue);
      if ( result==defaultValue || result>=lowerBound && result<=upperBound ) break;
      System.out.println("An integer between "+lowerBound+" and "+upperBound+" (inclusive) is required.");
    }
    return(result);
  }

  public static double readDouble(String fmt, Object... args) {
    String response = null;
    while(true) {
      try {
        response = System.console().readLine(fmt, args);
        if ( response!=null && response.length()>0 ) {
          return Double.parseDouble(response);
        }
        System.out.println("A number is required.");
      } catch (NumberFormatException e) {
        System.out.println("\""+response+"\" cannot be interpreted as a number!");
      }
    }
  }

  public static double readDouble(String prompt, double lowerBound, double upperBound) {
    while(true) {
      double result = readDouble(prompt);
      if ( result>=lowerBound && result<=upperBound ) {
        return(result);
      }
      System.out.println("A number between "+lowerBound+" and "+upperBound+" (inclusive) is required.");
    }
  }

  public static boolean readBoolean(String prompt) {
    String response = readString(prompt+" (y/N) : ");
    return response.trim().equalsIgnoreCase("Y");
  }

  public static java.io.Console systemConsole() {
    return theConsole;
  }

}