关于java:Java文件读写

前言

Java 文件读写能够分为字节流和字符流，之前始终没有好好演绎以下，借此机会做一个小笔记。

目录

字节流

字节流就是一个字节一个字节的传输，最罕用的就是 FileInputStream 和 FileOutputStream，代码如下

 public static void  readByFIS(String filepath) {File file = new File(filepath);
        try {FileInputStream fis = new FileInputStream(file);
            byte [] bytes = new byte[fis.available()];
            while (fis.read(bytes, 0, bytes.length) != -1) {System.out.println(new String(bytes));
            }
            fis.close();} catch (IOException e) {e.printStackTrace();
        }
    }

    public static void writeByFIS(String filepath) {File file = new File(filepath);
        if(!file.exists()) {
            try {file.createNewFile();
            } catch (IOException e) {e.printStackTrace();
            }
        }
        try {FileOutputStream fos = new FileOutputStream(file, true);
            fos.write("从此无可爱良夜，任他明月下西楼 \n".getBytes());
            fos.close();} catch (IOException e) {e.printStackTrace();
        }
    }

留神在读的的时候咱们使用了 available 去获取一个和文件大小刚好的空间，这存在一个问题，如果文件过大可能会导致内存溢出。

应用 BufferedInputStream 和 BufferedOutputStream 如下

public static void readByBIS(String filepath) {File file = new File(filepath);
        if(file.exists()) {
            try {BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));
                byte[] bytes = new byte[bis.available()];
                bis.read(bytes);
                System.out.println(new String(bytes));
                bis.close();} catch (IOException e) {e.printStackTrace();
            }
        }
    }

    public static void writeByBIS(String filepath) {File file = new File(filepath);
        if(!file.exists()) {
            try {file.createNewFile();
            } catch (IOException e) {e.printStackTrace();
            }
        }
        try {BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(filepath));
            bos.write("从此无可爱良夜，任他明月下西楼".getBytes());
            bos.flush();
            bos.close();} catch (IOException e) {e.printStackTrace();
        }
    }

字符流

使用 FileWriter 和 FileReader

public static void writeByFR(String filepath) {File file = new File(filepath);
        if(!file.exists()) {
            try {file.createNewFile();
            } catch (IOException e) {e.printStackTrace();
            }
        }
        try {FileWriter writer = new FileWriter(filepath, true);
            writer.write("从此无可爱良夜，任他明月下西楼");
            writer.close();} catch (IOException e) {e.printStackTrace();
        }
    }

    public static void readByFR(String filepath) {File file = new File(filepath);
        if(file.exists()) {
            try {FileReader reader = new FileReader(file);
                char[] chars = new char[100];
                reader.read(chars);
                System.out.println(chars);
                reader.close();} catch (IOException e) {e.printStackTrace();
            }
        }
    }

使用 BufferedWriter 和 BufferedReader

ublic static void readByBR(String filepath) {File file = new File(filepath);
        String line;
        try {BufferedReader reader = new BufferedReader(new FileReader(file));
            while ((line =  reader.readLine()) != null) {System.out.println(line);;
            }
            reader.close();} catch (IOException e) {e.printStackTrace();
        }
    }

    public static void writeByBR(String filepath) {File file = new File(filepath);
        if(!file.exists()) {
            try {file.createNewFile();
            } catch (IOException e) {e.printStackTrace();
            }
        }
        try {BufferedWriter writer = new BufferedWriter(new FileWriter(file, true));
            writer.write("从此无可爱良夜，任他明月下西楼");
            writer.flush();
            writer.newLine();
            writer.close();} catch (IOException e) {e.printStackTrace();
        }
    }

最初

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