一:java IO包概述
(一)Java读写文件,只能以(数据)流的形式进行读写
(二)java IO 包
–包装类
• 转化类:字节/字符/数据类型的转化类
• 装饰类:装饰节点类
(三)节点类
–InputStream, OutputStream(字节)
• FileInputStream,FileOutputStream
–Reader,Writer(字符)
• FileReader, FileWriter
(四)转换类:字符到字节之间的转化
–InputStreamReader:文件读取时字节,转化为Java能理解的字符
–OutputStreamWriter:Java将字符转化为字节输入到文件中
(五)装饰类:装饰节点类
–DataInputStream,DataOutputStream: 封装数据流
–BufferedInputStream,BufferOutputStream:缓存字节流
–BufferedReade, BufferedWriter:缓存字符流
二:文本文件读写
(一)写文件
–先创建文件,写入数据,关闭文件
–FileOutputStream, OutputStreamWriter, BufferedWriter
–BufferWriter
• write
• newLine
–try-resource 语句,自动关闭资源
–关闭最外层的数据流,将会把其上所有的数据流关闭
public static void writeFile1() {
FileOutputStream fos = null;
OutputStreamWriter osw = null;
BufferedWriter bw = null;
try {
fos = new FileOutputStream("c:/temp/abc.txt"); // 节点类
osw = new OutputStreamWriter(fos, "UTF-8"); // 转化类
//osw = new OutputStreamWriter(fos); // 转化类
bw = new BufferedWriter(osw); // 装饰类
// br = new BufferedWriter(new OutputStreamWriter(new
// FileOutputStream("c:/temp/abc.txt")))
bw.write("我们是");
bw.newLine();
bw.write("Ecnuers.^^");
bw.newLine();
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
bw.close(); // 关闭最后一个类,会将所有的底层流都关闭
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
public static void writeFile2() {
//try-resource 语句,自动关闭资源
try (BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("c:/temp/abc.txt")))) {
bw.write("我们是");
bw.newLine();
bw.write("Ecnuers.^^");
bw.newLine();
} catch (Exception ex) {
ex.printStackTrace();
}
}
(二)读文件
–先打开文件,逐行读入数据,关闭文件
–FileInputStream, InputStreamWriter, BufferedReade
–BufferReader
• readLine
–try-resource 语句,自动关闭资源
–关闭最外层的数据流,将会把其上所有的数据流关闭
public static void readFile1() {
FileInputStream fis = null;
InputStreamReader isr = null;
BufferedReader br = null;
try {
fis = new FileInputStream("c:/temp/abc.txt"); // 节点类
isr = new InputStreamReader(fis, "UTF-8"); // 转化类
//isr = new InputStreamReader(fis);
br = new BufferedReader(isr); // 装饰类
// br = new BufferedReader(new InputStreamReader(new
// FileInputStream("c:/temp/abc.txt")))
String line;
while ((line = br.readLine()) != null) // 每次读取一行
{
System.out.println(line);
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
br.close(); // 关闭最后一个类,会将所有的底层流都关闭
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
public static void readFile2() {
String line;
//try-resource 语句,自动关闭资源
try (BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream("c:/temp/abc.txt")))) {
while ((line = in.readLine()) != null) {
System.out.println(line);
}
}
catch(Exception ex)
{
ex.printStackTrace();
}
}
(三)混用写入和读取
public class FileW {
public static void main(String[] args) {
//写文件
FileOutputStream fos = null; //节点类
OutputStreamWriter osw = null; //转换类
BufferedWriter bw=null; //装饰类
try {
fos = new FileOutputStream("D:\MyJava\Code\JH16\test\aa\bb\E.txt");
osw = new OutputStreamWriter(fos);
bw = new BufferedWriter(osw);
//开始写入
bw.write("我们是:");
bw.newLine();
bw.write("fwawa!");
bw.newLine();
}catch(Exception e) {
System.err.println(e.getMessage());
}finally{
try {
bw.close();
}catch(Exception e) {
System.err.println(e.getMessage());
}
}
//读取文件
String line;
try(BufferedReader in =
new BufferedReader(
new InputStreamReader(
new FileInputStream("D:\MyJava\Code\JH16\test\aa\bb\E.txt")))){
while((line=in.readLine())!=null) {
System.out.println(line);
}
}catch(Exception e) {
System.err.println(e.getMessage());
}
}
}