IO流的复习笔记

IO字节流和缓冲流

IO字节流的读取和写入

读取

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class Test {
    public static void main(String[] args) {
        try (FileInputStream fis = new FileInputStream("java.txt")
        ) {
            byte[] bytes = new byte[40];
            int temp;
            while ((temp = fis.read(bytes)) != -1) {
                System.out.println(new String(bytes, 0, temp));
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

写入

import java.io.*;

public class Test {
    public static void main(String[] args) {
        try (FileOutputStream fos = new FileOutputStream("file" + File.separator + "1024.txt", true) //写入时不清除原有数据
        ) {
            fos.write("Hello".getBytes());
            fos.write("
".getBytes());  //换行
            fos.write("Wrold!".getBytes());
            fos.flush(); //刷新
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

IO字节流的文件拷贝

import java.io.*;

public class Test {
    public static void main(String[] args) {
        try (
                FileOutputStream fos = new FileOutputStream("file" + File.separator + "new.txt");
                FileInputStream fis = new FileInputStream("java.txt")
        ) {
            int temp;
            byte[] bytes = new byte[50];
            while ((temp = fis.read(bytes)) != -1) {
                fos.write(bytes);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

IO缓冲流的读取和写入

import java.io.*;

/**
 * IO缓冲字节流的读取
 */
public class Test {
    public static void main(String[] args) {
        try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream("java.txt"));
             BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "new.txt"));
        ) {
            int temp;
            while ((temp = bis.read()) != -1) {
                bos.write(temp);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 IO字符流和缓冲流

IO字符流的文件拷贝

import java.io.*;

/**
 * IO字符流的文件拷贝
 */
public class Test {
    public static void main(String[] args) {
        try (FileReader fr = new FileReader("java.txt");
             FileWriter fw = new FileWriter("file" + File.separator + "new.txt")
        ) {
            int temp;
            while ((temp = fr.read()) != -1) {
                fw.write(temp);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

IO缓冲字符流的文件拷贝

import java.io.*;

/**
 * IO缓冲字符流的文件拷贝
 */
public class Test {
    public static void main(String[] args) {
        try (
                BufferedReader br = new BufferedReader(new FileReader("java.txt"));
                BufferedWriter bw = new BufferedWriter(new FileWriter("file" + File.separator + "new.txt"))
        ) {
                String msg;
                while ((msg = br.readLine()) != null) {
                    bw.write(msg);
                    bw.newLine();  //换行
                    bw.flush();  //刷新
                }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

练习：图片简单的加密和解密

加密

import java.io.*;

/**
 * 图片的简单加密
 * 通过异或的方式
 */
public class Test {
    public static void main(String[] args) {
        try (
                BufferedInputStream bis = new BufferedInputStream(new FileInputStream("file" + File.separator + "123.jpg"));
                BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "new123.jpg"))
        ) {
            int temp;
            while ((temp = bis.read()) != -1) {
                bos.write(temp ^ 88);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

解密

import java.io.*;

/**
 * 图片的简单解密
 * 通过异或的方式
 */
public class Test {
    public static void main(String[] args) {
        try (
                BufferedInputStream bis = new BufferedInputStream(new FileInputStream("file" + File.separator + "code.jpg"));
                BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("file" + File.separator + "decode.jpg"))
        ) {
            int temp;
            while ((temp = bis.read()) != -1) {
                bos.write(temp ^ 88);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}