Question

输出应该是二进制到十进制的转换。当我运行此程序并输入（例如）101时，它将打印答案3次，因为101是3位数。我该如何解决？我只需要一个答案。请帮忙

    import java.util.Scanner;

    public class Bin2Dec {

public static void main (String[] args){
//Convert the input string to their decimal equivalent.
    //Open scanner for input.
        Scanner input = new Scanner(System.in);
        //Declare variable s.
        String s;

        //Prompt user to enter binary string of 0s and 1s.
        System.out.print("Enter a binary string of 0's and 1's: ");
        //Save input to s variable.
        s = input.nextLine();

        //Create a loop using the length of user input as the maximum number.
        for (int i=0;i< s.length();i++){
            try {
             System.out.println("The decimal value of the binary number "+ s +" is "+error(s));
              } catch (BinaryFormatException e) {
                System.out.println("There is an error in the entered binary string:"+e.getMessage());
              }
            }
          }

          public static int error(String parameter) throws BinaryFormatException {
            int tot = 0;
            for (int i = parameter.length(); i > 0; i--) {
              char c = parameter.charAt(i - 1);
              if (c == '1') tot += Math.pow(2, parameter.length() - i);
              else if (c != '0') throw new BinaryFormatException("'"+c+"' is not a binary digit");
            }
            return tot;
          } 
        }

Answer 1

您正在for循环中调用该方法：

for (int i=0;i< s.length();i++){
  try {
    System.out.println("The decimal value of the binary number "+ s +" is "+error(s));
  } catch (BinaryFormatException e) {
    System.out.println("There is an error in the entered binary string:"+e.getMessage());
  }
}

因此它当然会执行输入中字符数的次数。将呼叫转移到for error(s)。

Answer 2

你不应该尝试重新发明已经完成的事情。只需使用Integer#parseInt(String s, int radix)即可：

public class Bin2Dec {

    public static void main (String[] args){
        System.out.print("Enter a binary string of 0's and 1's: ");

        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine();

        int decoded = Integer.parseInt(input, 2);
        System.out.println(decoded);
    }
}

Answer 3

只需删除'for'循环，如下所示：

//Create a loop using the length of user input as the maximum number.   
//for (int i=0;i< s.length();i++){
        try {
            System.out.println("The decimal value of the binary number "+ s +" is "+error(s));
             } catch (Exception e) {
            System.out.println("There is an error in the entered binary      
          string:"+e.getMessage());
          }
        }
      //}

为什么这个程序根据用户输入的位数重复答案？

3 个答案: