java中io与file的简单了解

java中输入输出流的简单操作：

package com.ifly.classpractice.day7_30.io;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.PrintStream;

public class StreamDemo {

public static void main(String[] args) throws Exception {

writeFile1();
// writeFile2();

// readTextFile();
// readTextFile2();
}

private static void readTextFile2() throws Exception {
FileInputStream in = new FileInputStream("D:/text2.txt");
// System.out.println(in.available());
byte[] buffer = new byte[in.available()];
in.read(buffer);
// 将得到的字节数组转化为String
System.out.println(new String(buffer));
in.close(); // 关闭输入流

}

private static void readTextFile() throws Exception {
FileInputStream in = new FileInputStream("D:/text2.txt");

byte[] buffer = new byte[100];
while (in.read(buffer, 0, buffer.length) != -1) {
System.out.println(new String(buffer));
buffer = new byte[100];
}
in.close();
}

private static void writeFile2() throws Exception {
// 往文件中追加
FileOutputStream fos = new FileOutputStream("D:/text2.txt", true);

PrintStream ps = new PrintStream(fos);

for (int i = 0; i < 100; i++) {
// ps.println("i have a dream!\r\n");
ps.format("i have %s dream!\r\n", i);
ps.write(new String("I love java").getBytes());
}
ps.flush();
ps.close();
fos.close();

}

private static void writeFile1() throws Exception {
FileOutputStream fos = new FileOutputStream(new File("D:/text1.txt"));

for (int i = 0; i < 100; i++) {
byte[] bytes = String.format("I have %s dream!\r\n", i).getBytes();
fos.write(bytes);
}
fos.flush();
fos.close();

}

}

package com.ifly.classpractice.day7_30.io;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintStream;

public class FileReaderWriter {

public static void main(String[] args) throws IOException {
readerTextFile();
// writeTextFile();

// writeFile1();
// writeFile2();

// readTextFile();
// readTextFile2();

}

/**
* 用字符方式写文件
*
* @throws IOException
*/
private static void writeTextFile() throws IOException {
// FileWriter out = new FileWriter(new File("D:/studentsInfo.txt"));
FileWriter out = new FileWriter("D:/studentsInfo.txt", true);
// for (int i = 0; i < 10; i++) {
// out.write(String.format(" i have %s dream.\r\n", i));
// }

out.write("张三,1001,java3班\r\n");
out.write("李四,1002,java3班\r\n");
out.write("王五,1003,java3班\r\n");
out.write("小六,1004,java3班\r\n");
out.close();

}

/**
* 用字符方式读文件
*
* @throws IOException
*/
private static void readerTextFile() throws IOException {
FileReader in = new FileReader(new File("D:/studentsInfo.txt"));
int ch = -1;
while (-1 != (ch = in.read())) {
System.out.print((char) ch);
}
in.close();
}

private static void readTextFile2() throws Exception {
FileInputStream in = new FileInputStream("D:/text2.txt");
// System.out.println(in.available());
byte[] buffer = new byte[in.available()];
in.read(buffer);
// 将得到的字节数组转化为String
System.out.println(new String(buffer));
in.close(); // 关闭输入流

}

private static void readTextFile() throws Exception {
FileInputStream in = new FileInputStream("D:/text2.txt");

byte[] buffer = new byte[100];
while (in.read(buffer, 0, buffer.length) != -1) {
System.out.println(new String(buffer));
buffer = new byte[100];
}
in.close();
}

private static void writeFile2() throws Exception {
FileOutputStream fos = new FileOutputStream("D:/text2.txt", true);

PrintStream ps = new PrintStream(fos);

for (int i = 0; i < 100; i++) {
// ps.println("i have a dream!\r\n");
ps.format("i have %s dream!\r\n", i);
ps.write(new String("I love java").getBytes());
}
ps.flush();
ps.close();
fos.close();

}

private static void writeFile1() throws Exception {
FileOutputStream fos = new FileOutputStream(new File("D:/text1.txt"));

for (int i = 0; i < 100; i++) {
byte[] bytes = String.format("i have %s dream!\r\n", i).getBytes();
fos.write(bytes);
}
fos.flush();
fos.close();

}

private static void viewStudentInfoAll() {
FileReader out = null;
try {
out = new FileReader(new File("D:/studentsResult.txt"));
BufferedReader buffer = new BufferedReader(out);
String str = new String();
while ((str = buffer.readLine()) != null) {
System.out.println(str);
}

} catch (IOException e) {
e.printStackTrace();
} finally {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}

}

}

package com.ifly.classpractice.day7_30.io;

import static java.lang.System.out;

import java.io.File;

public class FileAndDirectory {

public static void main(String[] args) throws Exception {
out.println("当前目录"+System.getProperty("user.dir"));
File directory = new File("");
out.println(directory.exists());
out.println(directory.getPath());
out.println(directory.getAbsolutePath());
out.println(directory.getCanonicalPath());

File directory0 = new File("../src/com/ifly/classpractice/day7_30/io");
out.println(directory0.exists());
out.println(directory0.getPath());
out.println(directory0.getAbsolutePath());
out.println(directory0.getCanonicalPath());

File directory1 = new File("./src/com/ifly/classpractice/day7_30/io");
out.println(directory1.exists());
out.println(directory1.getPath());
out.println(directory1.getAbsolutePath());
out.println(directory1.getCanonicalPath());

}

}

@Test
public void newFileOrDeleteFile() throws IOException {
File file = new File("E:/demo.txt");

if (!file.exists()) {
file.createNewFile();
} else {
file.delete();
}

System.out.println(file.exists());

file.renameTo(new File("E:/demo.pdf")); // 重命名
}

@Test
public void testCopyFile() throws Exception {
copyFile("E:/d.txt", "E:/e.txt"); // 拷贝文件
}

/**
* 拷贝文件
*
* @param src
* @param dest
* @throws Exception
*/
public void copyFile(String src, String dest) throws Exception {
FileInputStream fis = new FileInputStream(src);
FileOutputStream fos = new FileOutputStream(dest);

FileChannel fcIn = fis.getChannel();
FileChannel fcOut = fos.getChannel();

fcIn.transferTo(0, fcIn.size(), fcOut);
fcOut.close();
fcIn.close();
fos.close();
fis.close();
}

@Test
public void testGetAllFile() throws Exception {
getAllFile3("D:/"); // 列出目录中的所有文件
}

public void getAllFile3(String string) throws Exception {
File[] files = new File(string).listFiles();
for (int i = 0; i < files.length; i++) {
if (files[i].isFile()) {
System.out.println(files[i].getCanonicalPath());
} else {
getAllFile3(files[i].getCanonicalPath());
}
}

}