Java自学-IO流(2)
1、递归求阶乘
package lesson02;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 20:05
* FileName: RecursionDemo01
* Description:
*/
public class RecursionDemo01 {
public static void main(String[] args) {
int result = jc(5);
System.out.println("5的阶乘为："+result);
}
public static int jc(int n){
if(n==1){
return 1;
}else{
return n*jc(n-1);
}
}
}
2、遍历目录
package lesson02;
import java.io.File;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 20:12
* FileName: RecursionDemo02
* Description:
*/
public class RecursionDemo02 {
public static void main(String[] args) {
File srcFile=new File("D:\\Java");
getAllFilePath(srcFile);
}
public static void getAllFilePath(File srcFile){
File[] fileArray = srcFile.listFiles();
if(fileArray !=null){
for(File file:fileArray){
if(file.isDirectory()){
getAllFilePath(file);
}else{
System.out.println(file.getAbsolutePath());
}
}
}
}
}
3、IO流概述和分类
4、字节流写数据
package lesson01;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 20:28
* FileName: FileOutputStreamDemo01
* Description:
*/
public class FileOutputStreamDemo01 {
public static void main(String[] args) throws IOException {
FileOutputStream fos = new FileOutputStream("fos.txt");
/*
做了三件事情:
A:调用系统功能创建了文件
B:创建了字节输出流对象
c:让字节输出流对象指向创建好的文件
*/
fos.write(97);
// fos.write(57);
// fos.write(55);
fos.close();
}
}
5、字节流写输入的三种方式
IDEA格式化快捷键：Ctrl+Alt+l
package lesson01;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 20:39
* FileName: FileOutputStreamDemo02
* Description:
*/
public class FileOutputStreamDemo02 {
public static void main(String[] args) throws IOException {
FileOutputStream fos = new FileOutputStream("fos.txt");
// File file = new File("fos.txt");
// FileOutputStream fos1 = new FileOutputStream(file);
// FileOutputStream fos2 = new FileOutputStream(new File("fos.txt"));
// fos.write(97);
// fos.write(98);
// fos.write(99);
// fos.write(100);
// fos.write(101);
// byte[] bys={97,98,99,100,101};
byte[] bys = "abcde".getBytes();
// fos.write(bys);
// fos.write(bys,0,bys.length);
fos.write(bys,1,3);
fos.close();
}
}
6、字节流写数据的两个小问题
package lesson01;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 20:52
* FileName: FileOutputStreamDemo03
* Description:
*/
/*
window : \r\n
linux: \n
mac:\r
*/
public class FileOutputStreamDemo03 {
public static void main(String[] args) throws IOException {
// FileOutputStream fos = new FileOutputStream("fos.txt");
FileOutputStream fos = new FileOutputStream("fos.txt",true);
for (int i = 0; i < 10; i++) {
fos.write("hello".getBytes());
fos.write("\r\n".getBytes());
}
fos.close();
}
}
7、字节流写数据加异常处理
package lesson01;
import java.io.FileOutputStream;
import java.io.IOException;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 21:03
* FileName: FileOutputStreamDemo04
* Description:
*/
public class FileOutputStreamDemo04 {
public static void main(String[] args) {
// try {
// FileOutputStream fos = new FileOutputStream("fos.txt");
// fos.write("hello".getBytes());
// fos.close();
// } catch (IOException e) {
// e.printStackTrace();
// }
FileOutputStream fos = null;
try {
fos = new FileOutputStream("fos.txt");
fos.write("hello".getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fos != null) {
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
8、字节流读数据(一次读一个字节数据)
package lesson02;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 21:13
* FileName: FileInputStreamDemo01
* Description:
*/
public class FileInputStreamDemo01 {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("fos.txt");
//第一次读取数据。
// int by = fis.read();
// System.out.println(by);
// System.out.println((char)by);
//
// //第二次读取数据。
// by = fis.read();
// System.out.println(by);
// System.out.println((char)by);
// int by=fis.read();
// while(by!=-1){
// System.out.print((char)by);
// by=fis.read();
// }
//优化
int by;
while((by=fis.read())!=-1){
System.out.print((char)by);
}
fis.close();
}
}
9、字节流复制文本文件
package lesson02;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 21:33
* FileName: CopyTxtDemo
* Description:
*/
public class CopyTxtDemo {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("D:\\Java\\test.txt");
FileOutputStream fos = new FileOutputStream("test.txt");
int by;
while((by=fis.read())!=-1){
fos.write(by);
}
fis.close();
fos.close();
}
}
10、字节流读数据(一次读一个字节数组数据)
package lesson02;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
* Author: Gu Jiakai
* Date: 2021/8/23 21:38
* FileName: FileInputStreamDemo02
* Description:
*/
public class FileInputStreamDemo02 {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("fos.txt");
// byte[] bys=new byte[5];
// int len=fis.read(bys);
// System.out.println(len);
//// System.out.println(new String(bys));
// System.out.println(new String(bys,0,len));
//
//// \r\nlov
// len=fis.read(bys);
// System.out.println(len);
//// System.out.println(new String(bys));
// System.out.println(new String(bys,0,len));
//
//// e\nlov
// len=fis.read(bys);
// System.out.println(len);
//// System.out.println(new String(bys));
// System.out.println(new String(bys,0,len));
byte[] bys=new byte[1024];//1024及其整数倍。
int len;
while((len=fis.read(bys))!=-1){
System.out.print(new String(bys,0,len));
}
fis.close();
}
}