OutputStream字节输出流

public abstratc class OutputStream
extends  Object
implements Closeable，Flushable{}

public interface Closeable 
extends AutoCloseable{
public void close() throws IOException;
}

public interface Flushable{
public void flush() throws IOException;
}

OutputStream类常用方法

方法	描述
public abstract void wirte(int b) throws IOException	输出单个字节数据
public void wirte(byte[] b) throws IOException	输出一组字节数据
public void wirte(byte[] b,int off,int len) throws IOException	输出部分字节数据
public void close() throws IOException	关闭输出流
public void flush() throws IOException	刷新缓冲区

FIleOutputStream类的主要目的就是为OutputStream父类实例化，以为OutputStream是抽象类

方法	描述
public FIleOutputStream(File file) throws FileNotFoundException	采用覆盖的形式创建文件输出流
public FIleOutputStream(File file,boolean append) throws FileNotFoundException	采用追加的形式创建文件输出流

public class javaIODemo {
 public static void main(String[] args) throws FileNotFoundException, IOException {
  File file = new File("f:" + File.separator + "javaIODemo" + File.separator + "message"
    + File.separator + "xiyang.txt");
  if(!file.getParentFile().exists()) {
   file.mkdirs();
  }
  //使用AutoCloseable自动关闭接口
  //自动关闭输出流
  try(OutputStream outputStream = new FileOutputStream(file,true)){
   String string = "www.baidu.com";
   outputStream.write(string.getBytes());
  }
 }
}

InputStream字节输出流

方法	描述
public abstract int read() throws IOException	读取单个字节数据，读到底返回-1
public int read(byte[] b) throws IOException	读取一组字节数据，返回的是读取的个数，读到底返回-1
public int read(byte[] b ,int off,int len) throws IOException	读取一组字节数据（只占数组的一部分）
public void close() throws IOException	关闭输出流
public byte[] readAlllBytes() throws IOException	读取输入流全部字节数据(JDK1.9之后)
public long transferTo(OutputStream out) throws IOException	输入流转为输出流（JDK1.9之后新增）

public class javaIODemo {
 public static void main(String[] args) throws IOException {
  File file = new File("f:" + File.separator + "javaIODemo" + File.separator + "message"
    + File.separator + "xiyang.txt");
  if(file.exists()) {
   InputStream input = new FileInputStream(file);
   byte data[] = new byte[1024];//数据读取缓冲区
   int len = input.read(data);
   System.out.println("[" + new String(data,0,len) +"]");
   input.close();
  }
 }
}

Writer字符输出流

writer类常用方法：

方法	描述
public Writer append(CharSequence csq) throws IOException	追加内容
public void write(char[] cbuf) throws IOException	输出字符数组
public void write(int c) throws IOException	输出单个字符
public void wirte(String str) throws IOException	输出字符串
public abstract void close() throws IOException	关闭输入流
public abstract void flush() throws IOException	刷新缓冲区

FileWriter类常用方法：

方法	描述
public FileWriter(File file) throws IOException	覆盖的形式创建文件输出流
public FileWriter(File file,boolean append) throws IOException	追加的形式创建文件输出流

public class javaIODemo {
 public static void main(String[] args) throws IOException {
  File file = new File("f:" + File.separator + "javaIODemo" + File.separator + "message"
    + File.separator + "xiyang.txt");
  if(!file.getParentFile().exists()) {
   file.getParentFile().mkdirs();
  }
  Writer out = new FileWriter(file);
  out.write("hello world");
  out.append(":do a java test");
  out.close();//字符流关闭时会自动刷新缓冲区
 }
}

Reader字符输入流

方法	描述
public int read() throws IOException	读取单个字符，无数据读取时返回-1
public int read(char cbuf) throws IOException	读取多个字符，并返回读取个数
public long skip(long n) throws IOException	跳过指定字符个数后读取
public boolean ready() throws IOException	是否可以开始读取数据
public abstract void close() throws IOException	关闭输入流

public class javaIODemo {
 public static void main(String[] args) throws IOException {
  File file = new File("f:" + File.separator + "javaIODemo" + File.separator + "message"
    + File.separator + "xiyang.txt");
  if(file.exists()) {
   Reader in = new FileReader(file);
   char []data = new char[1024];
   in.skip(3);
   int len = in.read(data);
   System.out.println(new String(data,0,len));
   in.close();
  }
 }
}

转换流

java.io中提供了两种转换流：OutputStreamWriter和InputStreamReader。
OutputStreamWriter:

public class OutputStreamWriter extends Writer{}
//[构造方法]public OutputStreamWriter(OutputStream out)

InputStreamReader：

public class InputStreamReader extends Reader{}
//[构造方法]public InputStreamReader(InputStream in)

InputStream和Reader的转换

 public static void main(String[] args) throws IOException {
  File file = new File("f:" + File.separator + "javaIODemo" + File.separator + "message"
    + File.separator + "xiyang.txt");
  if(!file.getParentFile().exists()) {
   file.getParentFile().mkdirs();
  }
  InputStream in = new FileInputStream(file);
  Reader reader = new InputStreamReader(in);
  char data[] = new char[1024];
  int len = reader.read(data);
  System.out.println(new String(data,0,len));
  reader.close();
  in.close();
 }

原文链接：https://blog.csdn.net/qq_45346915/article/details/113250427