java中RandomAccessFile类用法
RandomAccessFile类
只能访问文件，不能操作其他io设备
支持随机访问
在读写等长记录文件有优势
实例：
import java.io.*;class Employee {private String name;private int age;public static final int LEN = 8;String getName() {return name;}int getAge() {return age;}Employee(String name, int age) {if (name.length() > LEN) { // 为了构造等长记录this.name = name.substring(0, LEN-1);} else {this.name = name;while (this.name.length() < LEN) {this.name += '\u0000';}}this.age = age;}}public class RandomAccessFileTest {public static void main(String [] args) {Employee e1 = new Employee("Ronnie", 37);Employee e2 = new Employee("John", 37);Employee e3 = new Employee("Mark", 37);try {RandomAccessFile randFile = new RandomAccessFile("employee.txt", "rw");//randFile.write(e1.getName().getBytes()); // 如果name有中文，会出现问题，因为一个英文字符转换为一个字节，一个中文字符转换为两个字节，可以用writeChars函数改写randFile.writeChars(e1.getName()); //-randFile.writeInt(e1.getAge());//randFile.write(e2.getName().getBytes());randFile.writeChars(e1.getName()); //-randFile.writeInt(e2.getAge());//randFile.write(e3.getName().getBytes());randFile.writeChars(e1.getName()); //-randFile.writeInt(e3.getAge());randFile.close();} catch (Exception e) {e.printStackTrace();}try {//byte[] nameBuf = new byte[Employee.LEN];RandomAccessFile randFile = new RandomAccessFile("employee.txt", "r");//randFile.skipBytes(12);randFile.skipBytes(20); //-//int len = randFile.read(nameBuf);//String name = new String(nameBuf, 0, len);String name = "";//-for (int i = 0; i < Employee.LEN; ++i) { //-name += randFile.readChar(); //-}//-System.out.println(name.trim() + ":" + randFile.readInt());name = ""; //-randFile.seek(0); // 绝对定位//len = randFile.read(nameBuf);//name = new String(nameBuf, 0, len);for (int i = 0; i < Employee.LEN; ++i) { //-name += randFile.readChar(); //-} //-System.out.println(name.trim() + ":" + randFile.readInt());name = ""; //-//randFile.skipBytes(12);randFile.skipBytes(20); //-//len = randFile.read(nameBuf);//name = new String(nameBuf, 0, len);for (int i = 0; i < Employee.LEN; ++i) { //-name += randFile.readChar(); //-} //-System.out.println(name.trim() + ":" + randFile.readInt());randFile.close();} catch (Exception e) {e.printStackTrace();}}}
注释部分为按字节写入时的程序，带//-为原来的代码
其他函数请参照jdk文档