java - 从 bufferedreader 进行十六进制到十进制的转换

Question

我在让我的代码读取某个文件时遇到了很多麻烦，该文件有 4 个十六进制代码，使用缓冲区读取器并将其转换为十进制。我能够让 bufferreader 读取文本文件并将其输出到编译器，但我需要程序来存储 4 个值并让我的方法将十六进制转换为十进制。这是我到目前为止所拥有的:

import java.io.BufferedReader;
import static java.lang.System.*;
import java.io.*;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class HexToDecimal {

public static int hexToDecimal(String hexInput) throws IOException {
int decimal = 0;
int len = hexInput.length();

FileReader in = new FileReader("results.txt");
BufferedReader br = new BufferedReader(in);

String line;
while ((line = br.readLine()) != null) {
     out.printf(line + "\n");
}
in.close();


for (int i = 0; i < len; ++i) {
    char c = hexInput.charAt(i);
    int cValue;

    switch (c) {
    case '1':
        cValue = 1;
        break;
    case '2':
        cValue = 2;
        break;
    case '3':
        cValue = 3;
        break;
    case '4':
        cValue = 4;
        break;
    case '5':
        cValue = 5;
        break;
    case '6':
        cValue = 6;
        break;
    case '7':
        cValue = 7;
        break;
    case '8':
        cValue = 8;
        break;
    case '9':
        cValue = 9;
        break;
    case 'A':
        cValue = 10;
        break;
    case 'B':
        cValue = 11;
        break;
    case 'C':
        cValue = 12;
        break;
    case 'D':
        cValue = 13;
        break;
    case 'E':
        cValue = 14;
        break;
    case 'F':
        cValue = 15;
        break;
    default: // unexpected character
        throw new IllegalArgumentException("Non-hex character " + c
            + " found at position " + i);
    }
    decimal = 16 * decimal + cValue;
}
return decimal;

}

 public static void main(String[] args) { 

} 

}

此外，我无法使用 parseInt，这就是我使用大小写分隔符的原因。在将十六进制转换为十进制时，这也给我带来了麻烦。非常感谢任何帮助。

Answer 1

您可以通过这种方式更改代码，它会起作用:

import static java.lang.System.out;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.math.BigInteger;

public class HexToDecimal {

    public static BigInteger hexToDecimal(String hexInput) throws IOException {
        BigInteger decimal = BigInteger.ZERO;
        int len = hexInput.length();

        for (int i = len - 1; i >= 0; i--) {
            char c = hexInput.charAt(len - i - 1);
            BigInteger cValue;

            switch (c) {
            case '1':
                cValue = BigInteger.ONE;
                break;
            case '2':
                cValue = BigInteger.valueOf(2l);
                break;
            case '3':
                cValue = BigInteger.valueOf(3l);
                break;
            case '4':
                cValue = BigInteger.valueOf(4l);
                break;
            case '5':
                cValue = BigInteger.valueOf(5l);
                break;
            case '6':
                cValue = BigInteger.valueOf(6l);
                break;
            case '7':
                cValue = BigInteger.valueOf(7l);
                break;
            case '8':
                cValue = BigInteger.valueOf(8l);
                break;
            case '9':
                cValue = BigInteger.valueOf(9l);
                break;
            case 'A':
                cValue = BigInteger.valueOf(10l);
                break;
            case 'B':
                cValue = BigInteger.valueOf(11l);
                break;
            case 'C':
                cValue = BigInteger.valueOf(12l);
                break;
            case 'D':
                cValue = BigInteger.valueOf(13l);
                break;
            case 'E':
                cValue = BigInteger.valueOf(14l);
                break;
            case 'F':
                cValue = BigInteger.valueOf(15l);
                break;
            default: // unexpected character
                throw new IllegalArgumentException("Non-hex character " + c
                        + " found at position " + i);
            }
            decimal = decimal.add(cValue
                    .multiply(BigInteger.valueOf(16).pow(i)));
        }
        return decimal;

    }

    public static void main(String[] args) throws IOException {
        FileReader in = new FileReader("results.txt");
        BufferedReader br = new BufferedReader(in);

        String line;
        while ((line = br.readLine()) != null) {
            String[] hexNums = line.split(" ");
            for (String hex : hexNums)
                out.printf(hexToDecimal(hex) + "\n");
        }
        in.close();

    }

}

如果你必须使用大数字，那么你会得到一个错误的答案，使用 int 作为类型，所以你必须使用 BigInteger，然后代码看起来像上面一样，从文件读取并打印到输出流。我希望它有帮助。