如何将二进制数转换成十进制数？[闭门]

Question

我正试图编写一个程序，将二进制数字转换成相应的十进制值。虽然错误报告有效，但我似乎在这里得到了与输出相同的二进制数。fIdx是一种正向扫描仪，不进行任何计算。请帮忙！

import java.util.Scanner;
public class Bin2Dec {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String inStr;
        int inStrLen, decimal=0;
        boolean isValid;
        
        Scanner in = new Scanner (System.in);
        
        System.out.println("Enter a Binary string: ");
        inStr = in.next();
        inStrLen= inStr.length();
        in.close();
        
        
        isValid =true;
        for (int i=0; i < inStrLen; i++) {
            char inChar = inStr.charAt(i);
            
            if (!(inChar =='1' || inChar== '0')) {
                isValid=false;
                break;
            }       
                
        }   
        int fIdx=0, bIdx=inStrLen -1;
        while(fIdx <bIdx){
            if (inStr.charAt(++fIdx) =='1') {
                decimal += 2^fIdx;
            }
        }
        
            System.out.printf(!isValid?"error: invalid binary string " + inStr:"The equivalent decimal for binary " + 
            inStr ," is :%d" + decimal);
    }

}

Answer 1

你可以这样做：

    public static String convert_binary_to_string(String binary_string) 
{
    StringBuilder sb = new StringBuilder();
    Arrays.stream(binary_string.split("(?<=\\G.{8})")).forEach((String s) -> {
        sb.append( Integer.parseInt(s, 2));
    });
    return sb.toString();
}
public static void main(String[] args)
{
    System.out.println(convert_binary_to_string("0011001"));
}

您可以从用户输入中读取二进制值，在调用convert_binary_to_string之前在main方法中添加检查，然后在一切正常的情况下调用该方法。

Answer 2

你犯了几个错误：

1. 由于您正在预减量bIdx，初始值需要是inStrLen

int fIdx=0, bIdx=inStrLen;
while(bIdx > 0){
    if (inStr.charAt(--bIdx) =='1') {
        decimal += Math.pow(2, fIdx);
    }
    fIdx++;
}
       System.out.printf(!isValid? "Error: invalid binary string %s" :"The equivalent decimal for binary %s is: %d", inStr, decimal);

我曾经https://www.rapidtables.com/convert/number/binary-to-decimal.html验证答案。

示例运行：

Enter a Binary string: 
11011010
The equivalent decimal for binary 11011010 is: 218

Enter a Binary string: 
fdgdf
Error: invalid binary string fdgdf

此外，这是评估inStr

boolean isValid = true;
String regex = "^[0-1]+$";
if (!inStr.matches(regex)) {
    isValid = false;
}