java - RandomAccessFile 读取西里尔文 UTF-8 java

Question

伙伴们!

我在使用 RandomAccessFile 读取文件西里尔文本时遇到问题。

这是一个简单的程序，它使用以下格式将信息写入特定文件(西里尔字母):

keyLength、valueLength、key、value

然后程序尝试读取此信息，但我的输出不正确:

writing success
keyLength = 10, valueLength = 4
read: килло, гр

UPD预期输出:

writing success
keyLength = 10, valueLength = 4
read: киллограмм, сала

有什么问题吗？ (除了我脑子小的问题)

import java.io.FileNotFoundException;
import java.io.RandomAccessFile;
import java.io.IOException;

public class Main {

    public static void main(String[] args) {
        String fileName = "file.db";
        RandomAccessFile outputFile = null;

        try {
            outputFile = new RandomAccessFile(fileName, "rw");
        } catch (FileNotFoundException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }

        String key = "киллограмм";
        String value = "сала";

        try {
            outputFile.writeInt(key.length());
            outputFile.writeInt(value.length());

            outputFile.write(key.getBytes("UTF-8"));
            outputFile.write(value.getBytes("UTF-8"));
        } catch (IOException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }

        System.out.println("writing success");

        RandomAccessFile inputFile = null;

        try {
            inputFile = new RandomAccessFile(fileName, "r");
        } catch (FileNotFoundException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }

        int keyLength = 0, valueLength = 0;

        try {
            keyLength = inputFile.readInt();
            valueLength = inputFile.readInt();
        } catch (IOException e) {
            System.err.println(e.getMessage());
        }

        System.out.println("keyLength = " + keyLength + ", valueLength = " + valueLength);
        if (keyLength <= 0 || valueLength <= 0) {
            System.err.println("key or value length is negative");
            System.exit(1);
        }

        byte[] keyBytes = null, valueBytes = null;

        try {
            keyBytes = new byte[keyLength];
            valueBytes = new byte[valueLength];
        } catch (OutOfMemoryError e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }

        try {
            inputFile.read(keyBytes);
            inputFile.read(valueBytes);
        } catch (IOException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }

        try {
            System.out.println("read: " + new String(keyBytes, "UTF-8") + ", " + new String(valueBytes, "UTF-8"));
        } catch (IOException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }

    }
}

Answer 1

问题是这样的

outputFile.writeInt(key.length());

String#length()

Returns the length of this string. The length is equal to the number of Unicode code units in the string.

在本例中，它返回值 10，这不是表示此字符串所需的字节数。

你想要的是

key.getBytes("UTF-8").length

用作

byte[] keyBytes = key.getBytes("UTF-8");
outputFile.writeInt(keyBytes.length);

值相同。