Well, let’s take a look at the character stream
By the way, let’s talk about the character stream before doing a small case to get the previous knowledge
Exercise: Copy of files
public class Fdemo {
//复制文件
public static void main(String[] args) {
//字节输入
FileInputStream fi = null;
//字节输出
FileOutputStream fo =null;
String path="D:\\jj\\a2.txt";
try {
fi = new FileInputStream(path);
fo =new FileOutputStream("D:\\jj\\FuZhi.txt");
//遍历
int b;
while ((b=fi.read())!=-1){
fo.write(b);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
//释放资源
try {
fi.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
fo.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
1.1 FileWriter: File character output stream:
Role : writing the character data in memory to a file
Construction method:
FileWriter(File file) Construct a FileWriter object for a File object.
FileWriter(String fileName) Construct a FileWriter object with a given file name.
Use steps of file character output stream (emphasis):
1. Create a FileWriter object, bind the destination of the data to be written in the constructor
2. Use the method write in FileWriter to write data to the memory buffer (the process of converting characters to bytes)
3. The method in FileWriter will be flushed, and the data in the memory buffer will be flushed to the file
4.Release resources
/*
* 字符输出流【Writer】
* void write(int c) 写入单个字符。
void write(char[] cbuf) 写入字符数组。
abstract void write(char[] cbuf, int off, int len) 写入字符数组的某一部分,off数组的开始索引,
* len写的字符个数。
void write(String str) 写入字符串。
void write(String str, int off, int len) 写入字符串的某一部分,off字符串的开始索引,
* len写的字符个数。
void flush() 刷新该流的缓冲。
void close() 关闭此流，但要先刷新它。
* */
public class Fdemo07 {
//写出字符
public static void main(String[] args) throws IOException {
FileWriter fileWriter = null;
try {
fileWriter=new FileWriter("D:\\jj\\b.txt");
fileWriter.write(93);
fileWriter.write("我喜欢");
fileWriter.write("雷姆");
} catch (IOException e) {
e.printStackTrace();
}
/*
【注意】关闭资源时,与FileOutputStream不同。
如果不关闭,数据只是保存到缓冲区，并未保存到文件。
*/
fileWriter.close();
}
}
Other methods of writing data in character output stream
public class Fdemo08 {
//写出字符数组
public static void main(String[] args) {
FileWriter fileWriter = null;
try {
fileWriter=new FileWriter("D:\\jj\\b.txt");
char[] chars = "都拉都拉都拉都拉都拉都拉".toCharArray();
fileWriter.write(chars); //都拉都拉都拉都拉都拉都拉
fileWriter.write("奥里给"); //直接写字符串
fileWriter.write(chars,0,2); //写字符数组的一部分
fileWriter.write("奥里给",0,2); //写字符数组的一部分
} catch (IOException e) {
e.printStackTrace();
}
try {
fileWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
1.2 File character input stream
Character input stream Reader: is the top-level parent class of character input stream, defines some common member methods, and is an abstract class
Member method:
int read()Read a single character and returns
int read(char[] cbuf)Once read multiple characters, reading characters into an array
void close()Closes the stream and releases all associated resources
FileReader: File character input stream
Function: read the data in the hard disk file into the memory in the form of characters
Construction method:
FileReader(File file)Create a new FileReader, given a File read.
FileReader(String fileName)Creates a new FileReader, name of the file to be read given.
Parameters: the data source to read the file
String fileName: file path
File file: file
Steps to use character input stream:
1. Create a FileReader object and bind the data source
2. Use the method read in the FileReader object to read the file
3. Release resources
Let's have a king fried
int read() read a single file and return
public class Fdemo09 {
//写出字符数组
public static void main(String[] args) {
FileReader fileReader = null;
try {
fileReader=new FileReader("D:\\jj\\b.txt");
int b=0;
while ((b=fileReader.read())!=-1){
System.out.println((char)b);
}
} catch (IOException e) {
e.printStackTrace();
}
try {
fileReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
int read (char[] cbuf) Read multiple files at once, read characters into an array
public class Fdemo09 {
//写出字符数组
public static void main(String[] args) {
FileReader fileReader = null;
try {
fileReader=new FileReader("D:\\jj\\b.txt");
char[] chars = new char[1024];
int b=0; //每次读取的有效个数
while ((b=fileReader.read(chars))!=-1){
/*
String类的构造方法
String（char[] value）把字符数组转换为字符串
String（char[] value, int offset , int count）把字符数组的一部分转换为字符串， offset数组的开始索引 count转换的个数
*/
System.out.println(new String(chars,0,b));
}
} catch (IOException e) {
e.printStackTrace();
}
try {
fileReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}