程序清单:RandomFileTest.java
import java.io.*;
public class RandomFileTest
{
public static void main(String [] args) throws Exception
{
Employee e1 = new Employee("zhangsan",23);
Employee e2 = new Employee("Lisi",24);
Employee e3 = new Employee("Wangwu",25);
RandomAccessFile ra=new RandomAccessFile("c:\\1.txt","rw");
ra.write(e1.name.getBytes());
ra.writeInt(e1.age);
ra.write(e2.name.getBytes());
ra.writeInt(e2.age);
ra.write(e3.name.getBytes());
ra.writeInt(e3.age);
ra.close();
RandomAccessFile raf=new RandomAccessFile("c:\\1.txt","r");
int len=8;
raf.skipBytes(12); //跳过第一个员工的信息,其中姓名8字节,年龄4字节
System.out.println("第二个员工信息:");
String str="";
for(int i=0;i<len;i++)
str=str+(char)raf.readByte();
System.out.println("name:"+str);
System.out.println("age:"+raf.readInt());
System.out.println("第一个员工的信息:");
raf.seek(0); //将文件指针移动到文件开始位置
str="";
for(int i=0;i<len;i++)
str=str+(char)raf.readByte();
System.out.println("name:"+str);
System.out.println("age:"+raf.readInt());
System.out.println("第三个员工的信息:");
raf.skipBytes(12); //跳过第二个员工信息
str="";
for(int i=0;i<len;i++)
str=str+(char)raf.readByte();
System.out.println("name:"+str.trim());
System.out.println("age:"+raf.readInt());
raf.close();
}
}
class Employee
{
String name;
int age;
final static int LEN=8;
public Employee(String name,int age)
{
if(name.length()>LEN)
{
//*******************************下面一行代码,用了 this.name将出错,为什么?********
name = name.substring(0,8); }
else
{
while(name.length()<LEN)
name=name+"\u0000";
}
this.name=name;
this.age=age;
}
}
import java.io.*;
public class RandomFileTest
{
public static void main(String [] args) throws Exception
{
Employee e1 = new Employee("zhangsan",23);
Employee e2 = new Employee("Lisi",24);
Employee e3 = new Employee("Wangwu",25);
RandomAccessFile ra=new RandomAccessFile("c:\\1.txt","rw");
ra.write(e1.name.getBytes());
ra.writeInt(e1.age);
ra.write(e2.name.getBytes());
ra.writeInt(e2.age);
ra.write(e3.name.getBytes());
ra.writeInt(e3.age);
ra.close();
RandomAccessFile raf=new RandomAccessFile("c:\\1.txt","r");
int len=8;
raf.skipBytes(12); //跳过第一个员工的信息,其中姓名8字节,年龄4字节
System.out.println("第二个员工信息:");
String str="";
for(int i=0;i<len;i++)
str=str+(char)raf.readByte();
System.out.println("name:"+str);
System.out.println("age:"+raf.readInt());
System.out.println("第一个员工的信息:");
raf.seek(0); //将文件指针移动到文件开始位置
str="";
for(int i=0;i<len;i++)
str=str+(char)raf.readByte();
System.out.println("name:"+str);
System.out.println("age:"+raf.readInt());
System.out.println("第三个员工的信息:");
raf.skipBytes(12); //跳过第二个员工信息
str="";
for(int i=0;i<len;i++)
str=str+(char)raf.readByte();
System.out.println("name:"+str.trim());
System.out.println("age:"+raf.readInt());
raf.close();
}
}
class Employee
{
String name;
int age;
final static int LEN=8;
public Employee(String name,int age)
{
if(name.length()>LEN)
{
//*******************************下面一行代码,用了 this.name将出错,为什么?********
name = name.substring(0,8); }
else
{
while(name.length()<LEN)
name=name+"\u0000";
}
this.name=name;
this.age=age;
}
}
D:\>javac RandomFileTest.javaD:\>java RandomFileTest
第二个员工信息:
name:Lisi
age:24
第一个员工的信息:
name:zhangsan
age:23
第三个员工的信息:
name:Wangwu
age:25