java - 二进制到十进制转换 Java 代码错误

Question

所以我正在做一个项目，我必须进行从二进制数到十进制等的转换。这是我到目前为止的代码，有一个错误。在诸如 1101 之类的二进制数中，假设输出的十进制数是 13，但代码中输出的数字是 11。此错误发生在所有以一堆 1 开头且类似于单个 0 的二进制数中。

import java.util.*; // imports everything in java.util

public class newCalculator{

   * Conversion asks the user for a binary number.  It converts the input to a decimal number
   * using arrays and then displays the answer to the screen.
  */

  public static void main (String[]args){ // creates the main method
  binaryToDecimal(); //calls the user defined method binaryToDecimal
  }

  public static void binaryToDecimal() {
    Scanner scan = new Scanner(System.in); // Creates a new Scanner
    System.out.println("Input a Binary Number"); // Asks the user to input their number
    String binary = scan.next(); // Creates a new String that stores the value of the input
    char[] charArray = binary.toCharArray(); //Create a new Array and implements in the input
    double answer = 0;  // Creates a new double called answer setting it to zero
    for (double index = 0; index < charArray.length; index++){//For loop
      if (charArray[(int)index] == '1') {//If statement that allows the binary input to work
        answer = answer + Math.pow(2.0, index);//Sets the answer with the math class power of 2
      }
    }
    System.out.println(answer);//Prints out the final conversion result
     /* Test Cases   Expected Result   Output
   * 101                 5             5
   * 11                  3             3
   * 1                   1             1
   * 1101                13            11<--
   * 111                 7             7
   * 1000001             65            65
   * 1111                15            15
   * 1001                9             9
   * 11101               29            23<--
   * 10101               21            21
   * 
   */
  }

}

Answer 1

按照从右向左读取二进制字符串的方式计算您的预期结果；但是，您的代码从左到右读取二进制字符串。

更改此:

for (double index = 0; index < charArray.length; index++){

对此:

for (double index = charArray.length - 1; index >= 0; index--) {

您还应该更改为使用整数作为索引，如下所示:

for (int index = charArray.length - 1; index >= 0; index--) {