文件写入

import java.io.*;public class Main {public static void main(String[] args) {try {BufferedWriter out = new BufferedWriter(new FileWriter("sanguo.txt"));out.write("三国教程");out.close();System.out.println("文件创建成功！");} catch (IOException e) {}}}

以上代码运行输出结果为：

文件创建成功！

读取文件内容

import java.io.*;public class Main {public static void main(String[] args) {try {BufferedReader in = new BufferedReader(new FileReader("test.log"));String str;while ((str = in.readLine()) != null) {System.out.println(str);}System.out.println(str);} catch (IOException e) {}}}

以上代码运行输出结果为：

111222333

删除文件

import java.io.*;public class Main{public static void main(String[] args){try{File file = new File("c:\\test.txt");if(file.delete()){System.out.println(file.getName() + " 文件已被删除！");}else{System.out.println("文件删除失败！");}}catch(Exception e){e.printStackTrace();}}}

以上代码运行输出结果为(需要在 C 盘上先创建 test.txt 文件)：

test.txt 文件已被删除！

将文件内容复制到另一个文件

import java.io.*;public class Main {public static void main(String[] args) throws Exception {BufferedWriter out1 = new BufferedWriter(new FileWriter("srcfile"));out1.write("string to be copied\n");out1.close();InputStream in = new FileInputStream(new File("srcfile"));OutputStream out = new FileOutputStream(new File("destnfile"));byte[] buf = new byte[1024];int len;while ((len = in.read(buf)) > 0) {out.write(buf, 0, len);}in.close();out.close();BufferedReader in1 = new BufferedReader(new FileReader("destnfile"));String str;while ((str = in1.readLine()) != null) {System.out.println(str);}in1.close();}}

以上代码运行输出结果为：

string to be copied

向文件中追加数据

import java.io.*;public class Main {public static void main(String[] args) throws Exception {try {BufferedWriter out = new BufferedWriter(new FileWriter("filename"));out.write("aString1\n");out.close();out = new BufferedWriter(new FileWriter("filename",true));out.write("aString2");out.close();BufferedReader in = new BufferedReader(new FileReader("filename"));String str;while ((str = in.readLine()) != null) {System.out.println(str);}in.close();}catch (IOException e) {System.out.println("exception occoured"+ e);}}}

以上代码运行输出结果为：

aString1aString2

创建临时文件

//默认临时路径import java.io.*;public class Main {public static void main(String[] args) throws Exception {File temp = File.createTempFile("testrunoobtmp", ".txt");System.out.println("文件路径: "+temp.getAbsolutePath());temp.deleteOnExit();BufferedWriter out = new BufferedWriter(new FileWriter(temp));out.write("aString");System.out.println("临时文件已创建:");out.close();}}

// 指定临时路径import java.io.File;public class Main {public static void main(String[] args) {File f = null;try {// 创建临时文件f = File.createTempFile("tmp", ".txt", new File("C:/"));// 输出绝对路径System.out.println("File path: "+f.getAbsolutePath());// 终止后删除临时文件f.deleteOnExit();// 创建临时文件f = File.createTempFile("tmp", null, new File("D:/"));// 输出绝对路径System.out.print("File path: "+f.getAbsolutePath());// 终止后删除临时文件f.deleteOnExit();} catch(Exception e) {// 如果有错误输出内容e.printStackTrace();}}}

修改文件最后的修改日期

import java.io.File;import java.util.Date;public class Main {public static void main(String[] args) throws Exception {File fileToChange = new File("C:/myjavafile.txt");fileToChange.createNewFile();Date filetime = new Date(fileToChange.lastModified());System.out.println(filetime.toString());System.out.println(fileToChange.setLastModified(System.currentTimeMillis()));filetime = new Date(fileToChange.lastModified());System.out.println(filetime.toString());}}

以上代码运行输出结果为：

Sat Mar 21 22:00:48 CST trueFri Apr 10 11:09:19 CST

获取文件大小

import java.io.File;public class Main {public static long getFileSize(String filename) {File file = new File(filename);if (!file.exists() || !file.isFile()) {System.out.println("文件不存在");return -1;}return file.length();}public static void main(String[] args) {long size = getFileSize("c:/java.txt");System.out.println("java.txt文件大小为: " + size);}}

以上代码运行输出结果为（java.txt 文件位于 C 盘）：

java.txt文件大小为: 480

Java 文件操作一（写文件 按行读文件 删除文件 复制文件 追加数据 创建临时文件 修改最后修改日期 获取文件大小）