IO流
字节输入流 字节输出流 字符输入流 字符输出流
抽象基类 InputStream OutputStream Reader Writer
访问文件 FileInputStream FileOutputStream FileReader FileWriter
（节点流）
缓冲流 BufferedInputStream BufferedOutputStream BufferedReader BufferedWriter
（处理流）
操作对象 ObjectInputStream ObjectOutputStream
字节输入流：
* 1.创建一个FileInputStream对象
* 2.定义一个标记,Used to control the reading of the input stream
* 3.循环读取,如果读取到了-1,Indicates that the end of the file was read,循环结束
* 4.关闭资源.*****
一个一个的读
Create an array of bytes to output together
注意：We found that a stream is gone after reading it,不能再读了.
* Called by default when a stream has been readmark和resetmethod to record and reset,
* The stream has been reset to the position where it was last read,
* So the content cannot be read again.It is not that the stream is closed after reading once.
点击查看代码
@Test
public void test01() {
InputStream inputStream = null;
try {
inputStream = new FileInputStream("e:/aaa.txt");
// 开始读的操作,read方法,返回值是int,当返回值为-1时,The end of the file was read
// Read the end-of-file marker
int read;
// When the byte stream reads data, it is read byte by byte
// 循环读取
while((read = inputStream.read()) != -1) {
System.out.print(read + " ");
}
System.out.println();
System.out.println("读取完毕,再读一次....");
// When the byte stream reads data, it is read byte by byte
// 循环读取
while((read = inputStream.read()) != -1) {
System.out.print(read + " ");
}
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
try {
// 关闭流
inputStream.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
* 注意：We found that a stream is gone after reading it,不能再读了.
*
* Called by default when a stream has been readmark和resetmethod to record and reset,
* The stream has been reset to the position where it was last read,
* So the content cannot be read again.It is not that the stream is closed after reading once.
*
字节输出流
FileOutputStream构造器：
boolean append参数：如果传入true,It means to add on the original basis,不覆盖
如果传入false,或者不传,覆盖原有内容
写的操作,target file if it does not exist,会自动新建.
文件的复制
点击查看代码
public static void main(String[] args) {
InputStream inputStream = null; //文件的复制
OutputStream outputStream = null;
try {
int len;
byte[] bytes = new byte[10];
inputStream = new FileInputStream("D:/abc.txt");
outputStream = new FileOutputStream("D:/ych.txt");
while ((len=inputStream.read(bytes))!=-1){
outputStream.write(bytes,0,len);
}
System.out.println("文件复制成功");
} catch (FileNotFoundException e) {
throw new RuntimeException(e);
} catch (IOException e) {
throw new RuntimeException(e);
}finally {
try {
if (Objects.nonNull(inputStream)){
inputStream.close();
}
} catch (Exception e) {
throw new RuntimeException(e);
}
try {
if (Objects.nonNull(outputStream)){
outputStream.close();
}
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
字符流
输出数据
字符流
输入数据
* 字符处理流（用的最多）
* 缓冲流
*
* 只能处理纯文本文件：
* .txt,.java,.html,.css.........
*
* Write a copy of a file using a buffered character stream
缓冲字符流
输入数据
缓冲字符流
输出数据
* 外层流,内层流,The outer stream is closed,The inner stream will then be closed.
* We will eventually put it all together.class文件打包,Deploy this package to the server.
* 从始至终,.javaJust written by us programmers,给程序员看的.
* .javaNot even involved in packaging,does not appear on the server.
*
* The operation and maintenance personnel go to the server to deploy the project,It's a bunch of deployments.class.
* 我们的.propertiesProperties files are not involved in compilation.
序列化与反序列化：操作对象
* 序列化：将对象写入到IO流中,Turns an object of the memory model into a byte number,
* 可以进行存储和传输.
* 反序列化：从IO流中恢复对象,Data that will be stored on a hard drive or received from a network
* Revert to the object model
* 使用场景：所有可在网络上传输的对象都必须是可序列化的,
* 否则会报错,All objects stored on disk must also be serializable.
*
* 序列化版本号：
* 反序列化必须拥有class文件,但随着项目的升级,class文件也会升级
* Serialization guarantees compatibility before and after upgrades.
*
* javaSerialization provides a version number
* The version number can be freely specified,如果不指定,JVM会根据类信息自己计算一个版本号,
* 所以无法匹配,则报错！！！
*
* 不指定版本号,There is another danger,不利于JVM的移植,可能class文件没有改,
* 但是不同的jvmThe calculation rules are different,导致无法反序列化
*
* If only the method is modified,Deserialization is not affected,无需修改版本号
* Modified static variablesstatic,瞬态变量transient,Deserialization is also not affected,无需修改版本号
总结：
* 1.所有需要网络传输的对象都需要实现序列化接口
* 2.对象的类名、Instance variables are serialized;方法、类变量、transient变量不会被序列化
* 3.如果想让某个变量不被序列化,可以用transient修饰
* 4.序列化对象的引用类型成员变量,也必须是可序列化的,否则会报错
* 5.反序列化时必须有序列化对象的class文件
* 6.The same object is serialized multiple times,只有第一次序列化为二进制流,In the future, it just saves the serialized version number
* 7.It is recommended to add a version number to all serializable classes,方便项目升级.
