charAt()和Math.pow()

Question

背景:

我正在为类赋值创建一个简单的基本转换器.我相当接近完成但需要整理转换算法以将用户输入的值(在给定的基础中)转换为基数10的值.

尝试:

import java.util.Scanner;

public class BaseConverter {
public static void main(String[] args) {
    String numIn, intro1, prompt1, prompt2, output1;
    int baseIn;
    double numOut;
    boolean flag = true;
    Scanner kb = new Scanner(System.in);

    intro1 = "This program converts values in different number bases to a decimal value.";
    prompt1 = "Type in a number base (2 - 9): ";

    while (flag == true){
        System.out.println(intro1);
        System.out.println(prompt1);
        baseIn = kb.nextInt();
        //Checking base value for outliers outside given range
        if (baseIn < 2 || baseIn > 9) {
            System.out.println("Base must be between 2 and 9");
            System.exit(1);
        }
        prompt2 = "Type in a base "+baseIn+" number: ";
        System.out.println(prompt2);
        numIn = kb.next();

        // System.out.println(numStore);
        int counter = 0;
        // Let's pretend baseIn is 3 and i starts at 3 
        for (int i = numIn.length(); i >= 1; i--){
            numOut = (numIn.charAt(i-1) * Math.pow(baseIn, counter++));
            System.out.println(numOut);
        }
    }//while
}// method
}//class

问题:

此行不返回预期值

numOut = (numIn.charAt(i-1) * Math.pow(baseIn, counter++));

例如,在字符串"10"中,numOut应该是(0*(2*0))或在for循环的第一次迭代时为零.相反,它返回48.0.

我的想法:

我有一个潜行的怀疑,它与charAt()方法有关,因为调试Math.pow()方法显示它返回预期值.假设它与所有不同的变量类型有关？我不确定.

Answer 1

是的你是对charAt的问题.

当你输入let说"10"时,字符的整数值'0'是48,'1'根据Java用来编码字符的编码表,它的值是49.

如果你看一下它,你会看到0被编码为0x0030 = 3*16^1 = 481 0x0031 = 3*16^1 + 1*16^0 = 49,依此类推.

如果要获取角色本身的数值,可以使用

numOut = Character.getNumericValue(numIn.charAt(i-1)) * Math.pow(baseIn, counter++);