Java之文件的随机访问和读写RandomAccessFile

package FileDemo;

import java.io.IOException;
import java.io.RandomAccessFile;

public class RandomAccessFileDemo {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {

        writeAccess();
        readAccess();
        randomWrite();
    }

    // 随机写入数据，可以实现对已有数据的修改,因为可以使用seek()方法改变文件指针的位置
    private static void randomWrite() throws IOException {
        RandomAccessFile raf = new RandomAccessFile("random.txt", "rw");
        raf.seek(8 * 4);//将文件指针移动到指定位置
        System.out.println(raf.getFilePointer());
        raf.write("Ruby".getBytes());
        raf.writeInt(99);
    }

    private static void readAccess() throws IOException {
        RandomAccessFile raf = new RandomAccessFile("random.txt", "r");
        System.out.println(raf.getFilePointer());
        raf.seek(8);// 用于实现随机读取文件中的数据，数据最号有规律
        System.out.println(raf.getFilePointer());
        byte buf[] = new byte[4];
        raf.read(buf);
        String name = new String(buf);
        int age = raf.readInt();
        System.out.println("name=" + name);
        System.out.println("age=" + age);
        System.out.println(raf.getFilePointer());

    }

    private static void writeAccess() throws IOException {
        // rw:当这个文件不存在，会创建文件，当文件已经存在，不会创建，所以不会出现和输出流一样的覆盖
        RandomAccessFile raf = new RandomAccessFile("random.txt", "rw");
        raf.write("Java".getBytes());
        raf.writeInt(97);
        raf.write("python".getBytes());
        raf.write(98);
        raf.close();
    }

}