关于文件的读写操作

<pre name="code" class="java"><pre name="code" class="java">package io;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class WriteFileSupplement {

/**
* DataOutputStream写入数据，可以保证使用DataInputStream准确的读取数据--无论读写平台是多么的不同
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
write();
read();
}

private static void read() throws Exception {
DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream("Data.txt")));
System.out.println(in.readDouble());
System.out.println(in.readUTF());
System.out.println(in.readDouble());
System.out.println(in.readUTF());
System.out.println(in.readInt());
}

private static void write() throws Exception {
DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("Data.txt")));
out.writeDouble(3.1415926);
out.writeUTF("圆周率π");
out.writeDouble(1.1111111);
out.writeUTF("全1");
out.writeInt(123);
out.close();
}

}

package io;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.RandomAccessFile;import java.io.Reader;public
class ReadFileSupplement { /** * 以字节为单位读取文件，常用于读二进制文件，如图片、声音、影像等文件。 */ public static void readFileByBytes(String fileName) { File file = new File(fileName); InputStream in = null; try { System.out.println("以字节为单位读取文件内容，一次读一个字节："); // 一次读一个字节 in = new FileInputStream(file);
int tempbyte; while ((tempbyte = in.read()) != -1) { System.out.write(tempbyte); } in.close(); } catch (IOException e) { e.printStackTrace(); return; } try { System.out.println("以字节为单位读取文件内容，一次读多个字节："); // 一次读多个字节 byte[] tempbytes = new byte[100]; int byteread
= 0; in = new FileInputStream(fileName); ReadFileSupplement.showAvailableBytes(in); // 读入多个字节到字节数组中，byteread为一次读入的字节数 while ((byteread = in.read(tempbytes)) != -1) { System.out.write(tempbytes, 0, byteread); } } catch (Exception e1) { e1.printStackTrace();
} finally { if (in != null) { try { in.close(); } catch (IOException e1) { } } } } /** * 以字符为单位读取文件，常用于读文本，数字等类型的文件 */ public static void readFileByChars(String fileName) { File file = new File(fileName); Reader reader = null; try { System.out.println("以字符为单位读取文件内容，一次读一个字节：");
// 一次读一个字符 reader = new InputStreamReader(new FileInputStream(file)); int tempchar; while ((tempchar = reader.read()) != -1) { // 对于windows下，\r\n这两个字符在一起时，表示一个换行。 // 但如果这两个字符分开显示时，会换两次行。 // 因此，屏蔽掉\r，或者屏蔽\n。否则，将会多出很多空行。 if (((char) tempchar) != '\r') { System.out.print((char)
tempchar); } } reader.close(); } catch (Exception e) { e.printStackTrace(); } try { System.out.println("以字符为单位读取文件内容，一次读多个字节："); // 一次读多个字符 char[] tempchars = new char[30]; int charread = 0; reader = new InputStreamReader(new FileInputStream(fileName)); //
读入多个字符到字符数组中，charread为一次读取字符数 while ((charread = reader.read(tempchars)) != -1) { // 同样屏蔽掉\r不显示 if ((charread == tempchars.length) && (tempchars[tempchars.length - 1] != '\r')) { System.out.print(tempchars); } else { for (int i = 0; i < charread; i++) { if
(tempchars[i] == '\r') { continue; } else { System.out.print(tempchars[i]); } } } } } catch (Exception e1) { e1.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e1) { } } } } /** * 以行为单位读取文件，常用于读面向行的格式化文件 */ public
static void readFileByLines(String fileName) { File file = new File(fileName); BufferedReader reader = null; try { System.out.println("以行为单位读取文件内容，一次读一整行："); reader = new BufferedReader(new FileReader(file)); String tempString = null; int line = 1; // 一次读入一行，直到读入null为文件结束
while ((tempString = reader.readLine()) != null) { // 显示行号 System.out.println("line " + line + ": " + tempString); line++; } reader.close(); } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException
e1) { } } } } /** * 随机读取文件内容 */ public static void readFileByRandomAccess(String fileName) { RandomAccessFile randomFile = null; try { System.out.println("随机读取一段文件内容："); // 打开一个随机访问文件流，按只读方式 randomFile = new RandomAccessFile(fileName, "r"); // 文件长度，字节数 long
fileLength = randomFile.length(); // 读文件的起始位置 int beginIndex = (fileLength > 4) ? 4 : 0; // 将读文件的开始位置移到beginIndex位置。 randomFile.seek(beginIndex); byte[] bytes = new byte[10]; int byteread = 0; // 一次读10个字节，如果文件内容不足10个字节，则读剩下的字节。 // 将一次读取的字节数赋给byteread while
((byteread = randomFile.read(bytes)) != -1) { System.out.write(bytes, 0, byteread); } } catch (IOException e) { e.printStackTrace(); } finally { if (randomFile != null) { try { randomFile.close(); } catch (IOException e1) { } } } } /** * 显示输入流中还剩的字节数 */ private
static void showAvailableBytes(InputStream in) { try { System.out.println("当前字节输入流中的字节数为:" + in.available()); } catch (IOException e) { e.printStackTrace(); } } public static void main(String[] args) { String fileName = "src/a.txt"; ReadFileSupplement.readFileByBytes(fileName);
System.out.println(); ReadFileSupplement.readFileByChars(fileName); System.out.println(); ReadFileSupplement.readFileByLines(fileName); System.out.println(); ReadFileSupplement.readFileByRandomAccess(fileName); }}

package io;

import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

public class WriteFile {

/**
* 写文本文件可以使用PrintWriter，FileWriter，BufferedWrite
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
write("src/c.txt");
}

private static void write(String filename) throws Exception {
String dd = "src/d.txt";
System.out.println("FileWriter:");
FileWriter fw = new FileWriter(dd);
String s1 = "abc中文！";
fw.write(s1, 0, s1.length());
fw.flush();
fw.close();

System.out.println("PrintWriter");
PrintWriter pw = new PrintWriter(filename);
String s2 = "元旦";
pw.write(s2);
pw.flush();
pw.close();
}

}

package io;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class WriteFileSupplement {

/**
* DataOutputStream写入数据，可以保证使用DataInputStream准确的读取数据--无论读写平台是多么的不同
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
write();
read();
}

private static void read() throws Exception {
DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream("Data.txt")));
System.out.println(in.readDouble());
System.out.println(in.readUTF());
System.out.println(in.readDouble());
System.out.println(in.readUTF());
System.out.println(in.readInt());
}

private static void write() throws Exception {
DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("Data.txt")));
out.writeDouble(3.1415926);
out.writeUTF("圆周率π");
out.writeDouble(1.1111111);
out.writeUTF("全1");
out.writeInt(123);
out.close();
}

}