实例1：
删除指定目录下的所有空文件
import java.io.File;
public class DelDri {
public static void main(String[] args) {
File file =
new File(
"d:/IO");
File[] files = file.listFiles();
for (File file2 : files) {
if (file2.isDirectory()) {
File[] file3 = file2.listFiles();
if (file3.length ==
0) {
file2.delete();
}
}
}
}
}
实例2：
删除指定目录下的所有空文件
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
public class DelFile {
public static void main(String[] args) {
File file =
new File(
"D:/IO/");
file.
delete();
File[] file1 = file.listFiles();
for (File file2 : file1) {
if (file2.isDirectory()) {
System.out.println(
"这是个文件夹");
}
else {
if (file2.length() ==
0) {
file2.
delete();
}
}
}
}
}
实例3：
将D：/IO下的所有文件复制到目录D：/new_io
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class IO3 {
public void addFile(String string1, String string2) {
File file1 =
new File(string1);
File[] f = file1.listFiles();
for (File file : f) {
String string3 = string2;
String string4 = string1;
string3 +=
"/" + file.getName();
string4 +=
"/" + file.getName();
File file2 =
new File(string3);
if (file.isDirectory()) {
file2.mkdir();
System.out.println(
"文件夹建立完毕");
addFile(string4, string3);
}
else {
try {
file2.createNewFile();
@SuppressWarnings(
"resource")
FileInputStream fis =
new FileInputStream(string4);
@SuppressWarnings(
"resource")
FileOutputStream fos =
new FileOutputStream(string3);
byte[] data =
new byte[
1024];
int len;
while ((len = fis.read(data)) != -
1) {
String string =
new String(data,
0, len);
fos.write(string.getBytes());
}
}
catch (IOException e) {
e.printStackTrace();
}
}
}
}
public static void main(String[] args) {
IO3 io =
new IO3();
io.addFile(
"d:/IO",
"d:/new_io");
}
}
实例4：
用File类，在d:/io 目录中创建新的目录 test 在此目录中创建新的文件test.txt,使用BufferedWriter类写入5行数据，使用BufferedReader类读取出来，并显示到控制台
public class HomeWork1 {
public void Mymkdir(String
string, String string2) {
File file =
new File(
string);
if (!file.exists()) {
file.mkdirs();
}
string2 =
string + string2;
File file2 =
new File(
string);
if (!file2.exists()) {
try {
file2.createNewFile();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
public void ioOUT(String
string) {
try {
FileWriter fw =
new FileWriter(
string);
BufferedWriter bw =
new BufferedWriter(fw);
bw.write(
"古军");
bw.newLine();
bw.write(
"华是");
bw.newLine();
bw.write(
"山东");
bw.newLine();
bw.write(
"科技大学");
bw.newLine();
bw.write(
"学生");
fw.flush();
bw.flush();
fw.close();
bw.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
public void ioINT(String
string) {
try {
FileReader fr =
new FileReader(
string);
BufferedReader br =
new BufferedReader(fr);
String string2 =
null;
while ((string2 = br.readLine()) !=
null) {
System.
out.println(string2);
}
fr.close();
br.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
HomeWork1 homeWork1 =
new HomeWork1();
homeWork1.Mymkdir(
"d:/IO/test",
"test.txt");
String
string =
"d:/IO/test/test.txt";
homeWork1.ioOUT(
string);
homeWork1.ioINT(
string);
}
}
实例5：
使用File类获得指定文件的扩展名，比如，d:/io/IODemo.java显示java
public class HomeWork2 {
public void f1(String
string) {
File file =
new File(
string);
String string2 = file.getAbsolutePath();
int key = string2.lastIndexOf(
".");
for (
int i = key +
1; i < string2.length(); i++) {
System.
out.print(string2.charAt(i));
}
}
public static void main(String[] args) {
HomeWork2 homeWork2 =
new HomeWork2();
homeWork2.f1(
"dsjkfljslkfjsl.java");
}
}
实例6：
使用File类创建新文件，文件名为 当前时间.txt,格式示例如下：20170831163809.txt
public class HomeWork3 {
public void createFile(String
string) {
string =
"d:/IO/"+
string+
".txt";
File file =
new File(
string);
if (!file.exists()) {
try {
file.createNewFile();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
public String
data() {
Date date =
new Date();
SimpleDateFormat sf =
new SimpleDateFormat(
"yyyyMMddhhmmss");
String dateString = sf.format(date);
return dateString;
}
public static void main(String[] args) {
HomeWork3 homeWork3 =
new HomeWork3();
homeWork3.createFile(homeWork3.data());
}
}
