69期-Java SE-022-IO流-3-001-002

 

### 缓冲输出流

```java
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Test {
    public static void main(String[] args) {
        File file = new File("/Users/southwind/Desktop/test.txt");
        OutputStream outputStream;
        try {
            outputStream = new FileOutputStream(file);
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
            String str = "Java是一门面向对象的编程语言";
            byte[] bytes = str.getBytes();
            bufferedOutputStream.write(97);
            bufferedOutputStream.flush();
            bufferedOutputStream.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
```



### 序列化和反序列化

序列化就是将内存中的对象输出到硬盘文件中进行保存，反序列化就是将硬盘中保存的数据还原成内存中的对象。

- 序列化

```java
import java.io.Serializable;

public class User implements Serializable {
    private int id;
    private String name;
    private int age;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
}
```



```java
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;

public class Test2 {
    public static void main(String[] args) {
        User user = new User();
        user.setId(1);
        user.setName("张三");
        user.setAge(22);
        File file = new File("/Users/southwind/Desktop/java.txt");
        try {
            OutputStream outputStream = new FileOutputStream(file);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
            objectOutputStream.writeObject(user);
            objectOutputStream.flush();
            objectOutputStream.close();
            outputStream.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
```



- 反序列化

```java
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;

public class Test3 {
    public static void main(String[] args) {
        File file = new File("/Users/southwind/Desktop/java.txt");
        try {
            InputStream inputStream = new FileInputStream(file);
            ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
            User user = (User) objectInputStream.readObject();
            System.out.println(user.getId());
            System.out.println(user.getName());
            System.out.println(user.getAge());
            objectInputStream.close();
            inputStream.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
```



```java
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;

public class Test4 {
    public static void main(String[] args) {
        //使用IO流完成文件复制
        File file = new File("/Users/southwind/Desktop/1.jpg");
        try {
//            InputStream inputStream = new FileInputStream(file);
//            byte[] bytes = new byte[100];
//            int length = inputStream.read(bytes);
//            File file2 = new File("/Users/southwind/Desktop/test2.txt");
//            OutputStream outputStream = new FileOutputStream(file2);
//            outputStream.write(bytes,0,length);
            
            InputStream inputStream = new FileInputStream(file);
            File file2 = new File("/Users/southwind/Desktop/2.jpg");
            OutputStream outputStream = new FileOutputStream(file2);
            int temp = 0;
            while((temp = inputStream.read())!=-1) {
                outputStream.write(temp);
            }
            
//            Reader reader = new FileReader(file);
//            int temp = 0;
//            Writer writer = new FileWriter(file2);
//            while((temp = reader.read())!=-1) {
//                writer.write(temp);
//            }
//            writer.close();
//            reader.close();
            
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
```



```java
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;

public class Test5 {
    public static void main(String[] args) {
        File file = new File("/Users/southwind/Desktop/1.jpg");
        try {
//            InputStream inputStream = new FileInputStream(file);
//            BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
//            File file2 = new File("/Users/southwind/Desktop/2.jpg");
//            OutputStream outputStream = new FileOutputStream(file2);
//            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
//            int temp = 0;
//            while((temp = bufferedInputStream.read())!=-1) {
//                bufferedOutputStream.write(temp);
//            }
//            bufferedInputStream.close();
//            bufferedOutputStream.close();
//            inputStream.close();
//            outputStream.close();
            
            InputStream inputStream = new FileInputStream(file);
            Reader reader = new InputStreamReader(inputStream);
            BufferedReader bufferedReader = new BufferedReader(reader);
            File file2 = new File("/Users/southwind/Desktop/2.jpg");
            OutputStream outputStream = new FileOutputStream(file2);
            Writer writer = new OutputStreamWriter(outputStream);
            BufferedWriter bufferedWriter = new BufferedWriter(writer);
            int temp = 0;
            while((temp = bufferedReader.read())!=-1) {
                bufferedWriter.write(temp);
            }
            bufferedWriter.close();
            bufferedReader.close();
            reader.close();
            writer.close();
            inputStream.close();
            outputStream.close();
            
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
```



### 反射

常规情况下是通过类来创建实例化对象的，反射就是将这一过程进行反转，通过实例化对象来获取对应的类的信息。

### Class

Class 类是反射的源头，Class 类是专门用来描述其他类的类，Class 的每一个实例化对象就对应一个类的结构。

- 调用 Class 类的静态方法 forName(String className)，将目标类的全限定类名（包含所在包信息的类名全程）作为参数传入，即可获取对应的 Class 对象。

  ```java
  try {
    Class clazz = Class.forName("com.test.entity.User");
    System.out.println(clazz);
  } catch (ClassNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  }
  ```

- 通过目标类的 class 创建，Java 中的每一个类都可以调用 class，这里的 class 不是属性，叫做"类字面量"，其作用是获取内存中目标类型 class 对象的引用。

  ```java
  Class clazz2 = User.class;
  System.out.println(clazz2);
  ```

- 通过目标类实例化对象的 getClass() 方法创建，getClass() 方法定义在 Object 类中，被所有的类继承，通过实例化对象获取内存中改类 class 对象的引用。

  ```java
  User user = new User();
  Class clazz3 = user.getClass();
  System.out.println(clazz3);
  ```

Class 的常用方法

public native boolean isInterface()                                                                判断目标类是否为接口

public native boolean isArray()                                                                        判断目标类是否为数组

public native boolean isAnnotation()                                                            判断目标类是否为注解

public String getName()                                                                                    获取目标类的全限定类名

public native Class getSuperclass()                                                                获取目标类的父类

Test.java

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Test {
    public static void main(String[] args) {
        File file = new File("/Users/southwind/Desktop/test.txt");
        OutputStream outputStream;
        try {
            outputStream = new FileOutputStream(file);
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
            String str = "Java是一门面向对象的编程语言";
            byte[] bytes = str.getBytes();
            bufferedOutputStream.write(97);
            bufferedOutputStream.flush();
            bufferedOutputStream.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

 

Test.2java

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;

public class Test2 {
    public static void main(String[] args) {
        User user = new User();
        user.setId(1);
        user.setName("张三");
        user.setAge(22);
        File file = new File("/Users/southwind/Desktop/java.txt");
        try {
            OutputStream outputStream = new FileOutputStream(file);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
            objectOutputStream.writeObject(user);
            objectOutputStream.flush();
            objectOutputStream.close();
            outputStream.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

 

Test3.java

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;

public class Test3 {
    public static void main(String[] args) {
        File file = new File("/Users/southwind/Desktop/java.txt");
        try {
            InputStream inputStream = new FileInputStream(file);
            ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
            User user = (User) objectInputStream.readObject();
            System.out.println(user.getId());
            System.out.println(user.getName());
            System.out.println(user.getAge());
            objectInputStream.close();
            inputStream.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

 

Test4.java

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;

public class Test4 {
    public static void main(String[] args) {
        //使用IO流完成文件复制
        File file = new File("/Users/southwind/Desktop/1.jpg");
        try {
//            InputStream inputStream = new FileInputStream(file);
//            byte[] bytes = new byte[100];
//            int length = inputStream.read(bytes);
//            File file2 = new File("/Users/southwind/Desktop/test2.txt");
//            OutputStream outputStream = new FileOutputStream(file2);
//            outputStream.write(bytes,0,length);
            
            InputStream inputStream = new FileInputStream(file);
            File file2 = new File("/Users/southwind/Desktop/2.jpg");
            OutputStream outputStream = new FileOutputStream(file2);
            int temp = 0;
            while((temp = inputStream.read())!=-1) {
                outputStream.write(temp);
            }
            
//            Reader reader = new FileReader(file);
//            int temp = 0;
//            Writer writer = new FileWriter(file2);
//            while((temp = reader.read())!=-1) {
//                writer.write(temp);
//            }
//            writer.close();
//            reader.close();
            
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

 

Test5.java

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;

public class Test5 {
    public static void main(String[] args) {
        File file = new File("/Users/southwind/Desktop/test.txt");
        try {
            InputStream inputStream = new FileInputStream(file);
            BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
            File file2 = new File("/Users/southwind/Desktop/test2.txt");
            OutputStream outputStream = new FileOutputStream(file2);
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
            int temp = 0;
            while((temp = bufferedInputStream.read())!=-1) {
                bufferedOutputStream.write(temp);
            }
            bufferedInputStream.close();
            bufferedOutputStream.close();
            inputStream.close();
            outputStream.close();
            
//            InputStream inputStream = new FileInputStream(file);
//            Reader reader = new InputStreamReader(inputStream);
//            BufferedReader bufferedReader = new BufferedReader(reader);
//            File file2 = new File("/Users/southwind/Desktop/test2.txt");
//            OutputStream outputStream = new FileOutputStream(file2);
//            Writer writer = new OutputStreamWriter(outputStream);
//            BufferedWriter bufferedWriter = new BufferedWriter(writer);
//            String str = "";
//            while((str = bufferedReader.readLine())!=null) {
//                bufferedWriter.write(str);
//            }
//            bufferedWriter.close();
//            bufferedReader.close();
//            reader.close();
//            writer.close();
//            inputStream.close();
//            outputStream.close();
            
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

 

Test6.java

public class Test6 {
    public static void main(String[] args) {
        
    }
}

 

User.java

import java.io.Serializable;

public class User implements Serializable {
    private int id;
    private String name;
    private int age;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
}

 

Test.java

package com.test.entity;

public class Test {
    public static void main(String[] args) {
        try {
            Class clazz = Class.forName("com.test.entity.User");
//            System.out.println(clazz);
//            Class clazz2 = User.class;
//            System.out.println(clazz2);
//            User user = new User();
//            Class clazz3 = user.getClass();
//            System.out.println(clazz3);
//            System.out.println(clazz.hashCode());
//            System.out.println(clazz2.hashCode());
//            System.out.println(clazz3.hashCode());
//            System.out.println(clazz == clazz2);
//            System.out.println(clazz2 == clazz3);
            
            System.out.println(clazz.isInterface());
            System.out.println(clazz.isArray());
            System.out.println(clazz.isAnnotation());
            System.out.println(clazz.getName());
            System.out.println(clazz.getSuperclass());
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

 

User.java

package com.test.entity;

public class User {
    
}