java IO流_2
目录
字节缓冲流
使用对象流实现序列化
标准输入输出流
转换流
打印流
PrintStream
PrintWriter
properties读写文件
字节缓冲流
字节流
import java.io.FileInputStream;
import java.io.FileOutputStream;public class FileCopy {public static void main(String[] args) {//文件拷贝FileInputStream fileInputStream=null;//输入流FileOutputStream fileOutputStream=null;//输出流//源文件和目标文件String srcpath="C:\\\\Users\\\\Elysia\\\\Pictures\\\\Saved Pictures\\\\illust_86465238_20210124_003335.jpg";String destpath="D:\\\\javacode\\\\IO\\\\src\\\\pic.jpg";try {fileOutputStream=new FileOutputStream(destpath,true);fileInputStream=new FileInputStream(srcpath);byte[] buf=new byte[1024];int len;while((len=fileInputStream.read(buf))!=-1){fileOutputStream.write(buf,0,len);}} catch (Exception e) {e.printStackTrace();}finally {try {fileOutputStream.close();fileInputStream.close();}catch (Exception e){e.printStackTrace();}}}
}序列化
将java对象转化成字节序列，可以保存或传输，以备以后重新恢复。
意义：使得对象可以脱离程序，独立存在
前提：该对象的类支持序列化，必须实现两个接口之一
- Serializable 只是一个标记接口，无需实现任何方法
- Externalizble
#所有可能网络传输的对象，都应该是可序列化的类
使用对象流实现序列化
字节流，处理流，用于保存对象，传输对象。
步骤：
- 创建一个ObjectOutputStream，处理流，须建立在其他节点流之上
- 使用writeObject() 将对象序列化输出
反序列化
- 创建一个ObjectInputStream
- 调用readObject()方法读取流中的对象，若知道对象类型，可强转
package pack;import java.io.Serializable;
//实现Serializable
public class MidObj implements Serializable {private String name;private int data;public MidObj(String name, int data) {this.name = name;this.data = data;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getData() {return data;}public void setData(int data) {this.data = data;}
}
package Serialize;import java.io.FileOutputStream;
import java.io.ObjectOutputStream;import pack.MidObj;//导包很重要
public class Serialize {public static void main(String[] args) throws Exception{String path="D:\\\\javacode\\\\IO\\\\src\\\\Serialize\\\\obj.txt";MidObj obj=new MidObj("Serialize系列化",114);ObjectOutputStream objectOutputStream=new ObjectOutputStream(new FileOutputStream(path));objectOutputStream.writeObject(obj);objectOutputStream.close();}
}package Deserialize;import pack.MidObj;import java.io.FileInputStream;
import java.io.ObjectInputStream;public class Deserialize {public static void main(String[] args) throws Exception{String path="D:\\\\javacode\\\\IO\\\\src\\\\Serialize\\\\obj.txt";ObjectInputStream objectInputStream=new ObjectInputStream(new FileInputStream(path));MidObj midObj=(MidObj) objectInputStream.readObject();System.out.println(midObj.getName()+midObj.getData());objectInputStream.close();}
}细节：
- static和transient修饰的成员不会被序列化
- 建议添加 序列版本号 SerialVersionUID，提高版本兼容性
- 要求里面属性的类型也是实现序列化的
- 序列化具备可继承性，父类实现序列化，其所有子类也默认实现了
标准输入输出流
system.in 编译类型 InputStream
运行类型 BufferedInputStream
System.out 编译类型 PrintStream
运行类型 PrintStream
转换流
由于编码方式多种，容易导致乱码问题，因此需要转换流
Reader的子类
Charset 编码方式
Writer的子类
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;public class InputStreamReader_ {public static void main(String[] args) throws Exception{String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";String Charset="UTF-8";InputStreamReader inputStreamReader=new InputStreamReader(new FileInputStream(path),Charset);BufferedReader bufferedReader=new BufferedReader(inputStreamReader);String line;while((line=bufferedReader.readLine())!=null){System.out.println(line);}System.out.println("按照"+Charset+"读取文本");bufferedReader.close();}
}import java.io.BufferedWriter;
import java.io.FileOutputStream;
import java.io.OutputStreamWriter;public class OutputStreamWriter_ {public static void main(String[] args) throws Exception{String path="D:\\\\javacode\\\\IO\\\\src\\\\test.txt";String Charset="UTF-8";OutputStreamWriter outputStreamWriter=new OutputStreamWriter(new FileOutputStream(path),Charset);BufferedWriter bufferedWriter=new BufferedWriter(outputStreamWriter);bufferedWriter.write("按照UTF-8写入");bufferedWriter.close();//一定要关}
}
一定要关闭流
打印流
PrintStream
字节流，只有输出流
System.out就是字节打印流
import java.io.PrintStream;public class PrintStream_ {public static void main(String[] args) throws Exception{PrintStream out =System.out;out.println("666");out.write("hello".getBytes());//print底层就是writePrintStream ps=new PrintStream("D:\\\\javacode\\\\IO\\\\src\\\\test.txt");//输出到指定位置ps.println("Never can we suspend the time");ps.close();}
}
PrintWriter
字符流，只有输出流
import java.io.FileWriter;
import java.io.PrintWriter;public class PrintWriter_ {public static void main(String[] args) throws Exception{PrintWriter out=new PrintWriter(System.out);out.println("hello");out.close();//注意closePrintWriter pw=new PrintWriter(new FileWriter("D:\\\\javacode\\\\IO\\\\src\\\\test.txt",true));pw.println("成功写入");pw.close();}
}
properties读写文件
集合类，底层为hashTable
import java.io.FileReader;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.util.Properties;public class properties_ {
// public static void main(String[] args) throws Exception{
// String path="D:\\\\javacode\\\\IO\\\\src\\\\druid.properties";
// BufferedReader bufferedReader=new BufferedReader(new FileReader(path));
// String line;
// while((line=bufferedReader.readLine())!=null){
// String[] split=line.split("=");
// System.out.println(split[0]+"都值为"+split[1]);
// }
// bufferedReader.close();
// }public static void main(String[] args) throws Exception{Properties properties=new Properties();String path="D:\\\\javacode\\\\IO\\\\src\\\\druid.properties";String path0="D:\\\\javacode\\\\IO\\\\src\\\\druid0.txt";properties.load(new FileReader(path));properties.list(System.out);//打印流 字节打印流PrintWriter pw=new PrintWriter(new FileWriter(path0));properties.list(pw);//打印流pw.close();properties.setProperty("username","root1");System.out.println("\\nuser:"+properties.getProperty("username")+"\\npwd:"+properties.getProperty("password"));}
}import java.io.FileOutputStream;
import java.util.Properties;public class properties_1 {public static void main(String[] args) throws Exception{Properties properties=new Properties();properties.setProperty("username","root");properties.setProperty("password","111111");properties.setProperty("charset","UTF-8");String path="D:\\\\javacode\\\\IO\\\\src\\\\druid.properties";properties.store(new FileOutputStream(path),null);}
}
