知识大全 Java 中对文件的读写操作之比较
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Java 对文件进行读写操作的例子很多 让初学者感到十分困惑 我觉得有必要将各种方法进行 一次分析 归类 理清不同方法之间的异同点 一．在 JDK 中 通常是用 InputStream & OutputStream 这两个基类来进行读写操作的 InputStream 中的 FileInputStream 类似一个文件句柄 通过它来对文件进行操作 类似的 在 OutputStream 中我们有 FileOutputStream 这个对象 用FileInputStream 来读取数据的常用方法是 FileInputStream fstream = new FileInputStream(args[ ]); DataInputStream in = new DataInputStream(fstream); 用 in readLine() 来得到数据 然后用 in close() 关闭输入流 完整代码见 Example 用FileOutputStream 来写入数据的常用方法是 FileOutputStream out out = new FileOutputStream( myfile txt ); PrintStream p = new PrintStream( out ); 用 p println() 来写入数据 然后用 p close() 关闭输入 完整代码见 Example 二．在 JDK 中 支持两个新的对象 Reader & Writer 它们只能用来对文本文件进行操作 而 JDK 中的 InputStream & OutputStream 可以对文本文件或二进制文件进行操作 用FileReader 来读取文件的常用方法是 FileReader fr = new FileReader( mydata txt ); BufferedReader br = new BufferedReader(fr); 用 br readLing() 来读出数据 然后用br close() 关闭缓存 用fr close() 关闭文件 完整代码见 Example 用 FileWriter 来写入文件的常用方法是 FileWriter fw = new FileWriter( mydata txt ); PrintWriter out = new PrintWriter(fw); 在用out print 或 out println 来往文件中写入数据 out print 和 out println的唯一区别是后者写 入数据或会自动开一新行 写完后要记得 用out close() 关闭输出 用fw close() 关闭文件 完整代码见 Example Example : // FileInputDemo // Demonstrates FileInputStream and DataInputStream import java io *; class FileInputDemo public static void main(String args[]) // args length is equivalent to argc in C if (args length == ) try // Open the file that is the first mand line parameter FileInputStream fstream = new FileInputStream(args[ ]); // Convert our input stream to a DataInputStream DataInputStream in = new DataInputStream(fstream); // Continue to read lines while there are still some left to read while (in available() != ) // Print file line to screen System out println (in readLine()); in close(); catch (Exception e) System err println( File input error ); else System out println( Invalid parameters ); Example : // FileOutputDemo // Demonstration of FileOutputStream and PrintStream classes import java io *; class FileOutputDemo public static void main(String args[]) FileOutputStream out; // declare a file output object PrintStream p; // declare a print stream object try // connected to myfile txt out = new FileOutputStream( myfile txt ); // Connect print stream to the output stream p = new PrintStream( out ); p println ( This is written to a file ); p close(); catch (Exception e) System err println ( Error writing to file ); Example : // FileReadTest java // User FileReader in JDK to read a file import java io *; class FileReadTest public static void main (String[] args) FileReadTest t = new FileReadTest(); t readMyFile(); void readMyFile() String record = null; int recCount = ; try FileReader fr = new FileReader( mydata txt ); BufferedReader br = new BufferedReader(fr); record = new String(); while ((record = br readLine()) != null) recCount++; System out println(recCount + : + record); br close(); fr close(); catch (IOException e) System out println( Uh oh got an IOException error! ); e printStackTrace(); Example : // FileWriteTest java // User FileWriter in JDK to writer a file import java io *; class FileWriteTest public static void main (String[] args) FileWriteTest t = new FileWriteTest(); t WriteMyFile(); void WriteMyFile() try FileWriter fw = new FileWriter( mydata txt ); PrintWriter out = new PrintWriter(fw); out print( hi this will be wirte into the file! ); out close(); fw close(); catch (IOException e) System out println( Uh oh got an IOException error! ); e printStackTrace(); cha138/Article/program/Java/JSP/201311/19453相关参考