RandomAccessFile:
翻译过来就是任意修改文件,可以从文件的任意位置进行修改,迅雷的下载就是通过多个线程同时读取下载文件。例如,把一个文件分为四
部分,四个线程同时下载,最后进行内容拼接
public class RandomAccessFile implements DataOutput, DataInput, Closeable { public RandomAccessFile(String name, String mode); public RandomAccessFile(File file, String mode); }
RandomAccessFile实现了DataOutput和DataInput接口,说明可以对文件进行读写
有两种构造方法,一般使用第二种方式
第二个参数mode,有四种模式
代码实例:
@Data @NoArgsConstructor @AllArgsConstructor @ToString public class Student { private int id; private String name; private int sex; } public static void main(String[] args) throws Exception{ String filePath = "D:" + File.separator + "a.txt"; RandomAccessFile accessFile = new RandomAccessFile(new File(filePath), "rw"); Student student = new Student(1004, "sam", 1); accessFile.writeInt(student.getId()); accessFile.write(student.getName().getBytes()); accessFile.writeInt(student.getSex()); }
打开a.txt:
发现内容为乱码,这是因为系统只识别ANSI格式的写入,其他格式都是乱码。当然如果你在软件、IDE书写txt文件,打开没有乱码,是因为
已经替我们转格式了。
writeUTF():
public static void main(String[] args) throws Exception{ String filePath = "D:" + File.separator + "a.txt"; RandomAccessFile accessFile = new RandomAccessFile(new File(filePath), "rw"); Student student = new Student(1004, "sam", 1); // accessFile.writeInt(student.getId()); // accessFile.write(student.getName().getBytes()); // accessFile.writeInt(student.getSex()); accessFile.writeUTF(student.toString()); }
writeUTF()以与系统无关的方式写入,而且编码为utf-8,打开文件:
文件读取:
public static void main(String[] args) throws Exception{ String filePath = "D:" + File.separator + "a.txt"; RandomAccessFile accessFile = new RandomAccessFile(new File(filePath), "rw"); Student student = new Student(); String s = accessFile.readUTF(); System.out.println(s); }
输出结果:
Student(id=1004, name=sam, sex=1)
这里需要注意,如果是先写文件,然后立刻读取,需要调用accessFile.seek(0);把指针指向首位,因为文件写入最终指针指向末尾了。=
追加内容到末尾:
public static void main(String[] args) throws Exception{ String filePath = "D:" + File.separator + "a.txt"; RandomAccessFile accessFile = new RandomAccessFile(new File(filePath), "rw"); accessFile.seek(accessFile.length()); accessFile.write("最佳内容".getBytes()); }
我们首先把指针移动到文件内容末尾
原文地址:https://www.cnblogs.com/huigelaile/p/11047101.html
时间: 2024-10-08 01:47:36