通过RandomAccessFile实现一份文件存储多个对象再拿出来

其实通过RandomAccessFile存储是一个很大的byte数组，将对象存放与该数组中再存入文件中，可以实现读取和写入等等。

每个对象必须占有相同大小的字节，这样拿出来的时候才不至于乱

package com.iotek.otherio;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Scanner;

public class RandomAccessFileDemo {

public static void main(String[] args) throws IOException {
Person[] persons={new Person("zhangsan",20),new Person("lisi",80),new Person("wangwu",10),new Person("zhaoliu",50)};
RandomAccessFile random=new RandomAccessFile("E:/大一课程/java编程/所有待复制/randomaccessfile.txt","rw");
for(int i=0;i<persons.length;i++){
random.writeChars(persons[i].getName());
random.writeInt(persons[i].getAge());
}
//读取指定位置上的Person对象
Scanner scanner=new Scanner(System.in);
System.out.println("请输入要读取第几个Person对象");
int a=scanner.nextInt();
//使用seek方法来读取对象存放的位置
random.seek((a-1)*Person.size());
Person person=new Person();
person.setName(readName(random));
person.setAge(random.readInt());
System.out.println(person);

}
private static String readName(RandomAccessFile randomAccessFile) throws IOException{
char[] name=new char[15];
Character character=null;
int index=0;
for(int i=0;i<name.length;i++){
name[i]=randomAccessFile.readChar();
character=new Character(name[i]);
if(!character.equals('\u0000')){
index++;
}
}
return (new String(name)).replace('\u0000',' ').substring(0, index);
}
}
class Person{
private String name;
private int age;//占四个字节

public Person() {
super();
}
public Person(String name, int age) {
super();
StringBuilder builder=null;
if(name!=null){
builder=new StringBuilder(name);
}else{
builder=new StringBuilder(15);//源码中显示默认是16个字符容量，我们指定为15个字符容量（30个字节）
}
builder.setLength(15);//固定长度为15个
this.name = builder.toString();
this.age = age;
}
public String getName() {
return name;
}

public void setName(String name) {
this.name=name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
//返回每个对象所占内存大小
public static int size(){
return 34;
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + "]";
}
}