Java -如何通过字节读取.dat文件
Java -如何通过字节读取.dat文件
提问于 2016-08-13 16:35:10
我正在尝试使用没有其他类的Java来读取.dat。这是文件的结构:标题序列: Word；//2字节文件名: String255；//1字节日期: Word；//2字节FieldNumbers: Word；//2字节NumbersOfRecords: Word；//2字节
Info about Fields
FieldCode: Word; //2 bytes
FieldName: ShortString; //1 byte
Info in Field
FieldCode: Word; //2 bytes
FieldText: String[255]; //1 byte
DateTime = double我必须知道的是如何使用BufferedReader获取每个字节，将其作为int读取，然后将相同的int转换为字符串并显示在屏幕上。我可以创建不同的方法来读取每种类型的数据吗？我能让它同时读取两个字节吗？
更新：
package binarios5;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class Main5
{
public static void main(String[] args) throws FileNotFoundException, IOException
{
try
{
Path path = Paths.get("C:\\\\Dev-Pas\\\\EXAMEN2.dat");
System.out.println("File open");
byte[] bytes = Files.readAllBytes(path);
ByteBuffer buffer = ByteBuffer.wrap(bytes);
buffer.order(ByteOrder.BIG_ENDIAN);
short serial = buffer.getShort();
System.out.println("----[CONTENIDO DEL ARCHIVO]--------------------");
System.out.println("Nro. de Serie: " + serial);
int largoCadena = buffer.get();//Bytes 1 int Longitud de la cadena
//System.out.println("largoCadena: " + largoCadena);//33
byte[] bytesChar = new byte[largoCadena];//CString
buffer.get(bytesChar);
String nombre = new String(bytesChar, StandardCharsets.ISO_8859_1);
System.out.println("Nombre: " + nombre);
short date = buffer.getShort();//FALTA DECODIFICAR FECHA
System.out.println("Fecha sin procesar. "+date);//FALTA DECODIFICAR FECHA
short cantCampos = buffer.getShort(); //cantidad de campos que tienen los registros
System.out.println("Cantidad de Campos Customizados: "+cantCampos);//debe decir 4
int[] codCampo = new int[cantCampos];
String[] nombreCampo = new String[10];
for (int i = 0; i < cantCampos; i++) //leer RegType segun la cantidad de campos
{
codCampo[i] = buffer.getShort();//Bytes 2 codigo del campo
int largoCadena2 = buffer.get();//Bytes 1 int Longitud de la cadena
byte[] bytesChar2 = new byte[largoCadena2];
buffer.get(bytesChar2);
nombreCampo[i] = new String(bytesChar2, StandardCharsets.ISO_8859_1);
}
for (int i = 0; i < cantCampos; i++)//mostrar codigos y campos
{
System.out.println("Campo [codigo: " + codCampo[i] + ", descripcion: " + nombreCampo[i] + "]");
}
short cantRegistros = buffer.getShort();//cantidad de registros total
System.out.println("Cantidad de Registros: "+cantRegistros);
System.out.println("-----------------------");//OK
String[] contenidoCampo = new String[10];
for (int i = 0; i < cantRegistros; i++) //leyendo RegData 5 veces
{
short cantCamposCompletos = buffer.getShort();
for (int j = 0; j < cantCamposCompletos; j++)
{
short codCampoInterno = buffer.getShort();
int largoCadena3 = buffer.get();
byte[] bytesChar3 = new byte[largoCadena3];
buffer.get(bytesChar3);
contenidoCampo[j] = new String(bytesChar3, StandardCharsets.ISO_8859_1);
System.out.println(nombreCampo[j]+": "+contenidoCampo[j]);
}
System.out.println("-----------------------");
}
System.out.println("----[FIN CONTENIDO DEL ARCHIVO]-----------------");
}
catch (IOException e)
{
System.out.println("File I/O error!");
}
}
}回答 2
Stack Overflow用户
回答已采纳
发布于 2016-08-13 17:08:24
在java和Writer中，用于Unicode文本、字符串、2字节字符.
对于二进制数据，byte[] one需要一个InputStream，OutputStream。
您可以使用InputStream：
BufferedInputStream in = new BufferedInputStream(new FileInputStream(...));在你的例子中，你想读短文之类的。为此，您可以将其封装在DataInputStream中。
然而，首先使用ByteBuffer是最容易的。它可以从文件(FileChannel)中读取，但简单的情况是：
Path path = Paths.get("C:/xxx/yyy.dat");
byte[] bytes = Files.readAllBytes(path);
ByteBuffer buffer = ByteBuffer.wrap(bytes);
//buffer.order(ByteOrder.LITTLE_ENDIAN); // So short is read as LSB,MSB计算出：
// Header
short serial = buffer.getShort();
byte[] fileNameB = new byte[255];
buffer.get(fileNameB);
// If 0 terminated asciz string:
int len = fileNameB.length;
for (int i = 0; i < fileNameB.length; ++i) {
if (fileNameB[i] == 0) {
len = i;
break;
}
}
String fileName = new String(fileNameB, 0, len, StandardCharsets.ISO_8859_1);
short date = buffer.getShort();
short fieldNumbers = buffer.getShort();
short numbersOfRecords = buffer.getShort();
for (int fieldI = 0; fieldI < fieldNumber; ++fieldI) {
// Info about Fields
short fieldCode = buffer.getShort();
//byte fieldName: ShortString; //1 byte
}字段FieldCode中的信息: Word；//2字节FieldText: String255；//1字节
DateTime = doubleString getPascalString(ByteBuffer buffer) {
int length = buffer.get() & 0xFF;
byte[] bytes = new byte[length];
buffer.get(bytes);
return new String(bytes, StandardCharsets.ISO_8859_1);
}将交付：
d:/documentos/te...
short packedDate = buffer.getShort();
int year = packedDate & 0x7F; // + 1900?
int month = (packedDate >> 7) & 0xF:
int day = (packedDate >> 11) & 0x1F;Stack Overflow用户
发布于 2016-08-13 17:04:23
读者是用来阅读字符流的。要读取原始字节流，请考虑使用InputStream并调用
public int read(byte[] b)要解析字符串，将字节数组传递给指定编码的字符串构造函数(不要使用默认编码，因为它可能是utf8，这取决于您的环境，在您的情况下是不合适的)。
https://docs.oracle.com/javase/tutorial/essential/io/index.html
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/38934793
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