相对于文本文件，二进制文件读写快，定位快而准，下面是代码示例：
import java.io.DataInput;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.List;class Employee{
public static int RecordSize=72;// 总计8+30*2+4=72字节，算准总字节数对于连续读取很重要
private long id;// long类型似占8字节
private String name;
public static int NameSize=30;// 预计名称最多30个字符，占30*2=60字节
private int age;// int类型占4字节public Employee(long id,String name,int age){
this.id=id;
this.name=name;
this.age=age;
}public String toString(){
return "ID="+id+" name:"+name+" age:"+age;
}public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
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;
}
}public class Test3{
public static void main(String[] args) throws Exception{
// 准备数据
List<Employee> ls=new ArrayList<Employee>();final int AMOUT=10;
for(long i=0;i<AMOUT;i++){
ls.add(new Employee(i,"克隆人-"+i,(int)(i %100)));
}// 写入
DataOutputStream out=new DataOutputStream(new FileOutputStream("C:\\Users\\IBM_ADMIN\\Desktop\\emp.dat"));
for(Employee emp:ls){
writeEmp(out,emp);
}// 挨个读取
RandomAccessFile in=new RandomAccessFile("C:\\Users\\IBM_ADMIN\\Desktop\\emp.dat","r");
int len=(int)(in.length()/Employee.RecordSize);for(long i=0;i<len;i++){
in.seek(i*Employee.RecordSize);Employee emp=readEmp(in);
System.out.println(emp.toString());
}
}private static void writeEmp(DataOutput out,Employee emp) throws Exception{
writeString(emp.getName(),Employee.NameSize,out);
out.writeLong(emp.getId());
out.writeInt(emp.getAge());
}private static Employee readEmp(DataInput in) throws Exception{
String name=readString(Employee.NameSize,in);
long sn=in.readLong();
int age=in.readInt();return new Employee(sn,name,age);
}// 写入最大长度为size的字符串，不足写0
private static void writeString(String str,int size,DataOutput out) throws Exception{
for(int i=0;i<size;i++){
char c=0;
if(i<str.length()){
c=str.charAt(i);
}
out.writeChar(c);
}
}// 读入最大长度为size的字符串
private static String readString(int size,DataInput in) throws Exception{
StringBuilder sb=new StringBuilder();for(int i=0;i<size;i++){
char c=in.readChar();if(c==0){
continue;
}else{
sb.append(c);
}
}return sb.toString();
}
}
输出如下：
ID=0 name:克隆人-0 age:0
ID=1 name:克隆人-1 age:1
ID=2 name:克隆人-2 age:2
ID=3 name:克隆人-3 age:3
ID=4 name:克隆人-4 age:4
ID=5 name:克隆人-5 age:5
ID=6 name:克隆人-6 age:6
ID=7 name:克隆人-7 age:7
ID=8 name:克隆人-8 age:8
ID=9 name:克隆人-9 age:9