Question

java里如何从一个文件中读取多条记录

在java中，如何读取多条记录（记录格式例如name,age,wage）,读入后如何能实现插入新的记录和原来的记录一起保存到原来的文件中？
java新人。。求助~~

Answer 1

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class SimRecorder {

public List<Worker> kenWorkers(File data) {
List<Worker> workers = new ArrayList<Worker>();
try {
BufferedReader san = new BufferedReader(new FileReader(data));
String line = null;
while ((line = san.readLine()) != null) {
String[] args = line.split(",");
if (args.length >= 3) {
try {
Worker worker = new Worker(args[0], Integer
.parseInt(args[1].trim()), Integer
.parseInt(args[2].trim()));
workers.add(worker);
} catch (Exception e) {
System.err.println("参数有误!");
}
}

}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return workers;
}

public boolean save(List<Worker> workers, File data) {
StringBuffer cons = new StringBuffer();
for (Worker o : workers) {
cons.append(o.getName() + "," + o.getAge() + "," + o.getWage()
+ "\r\n");
}
try {
FileWriter writer = new FileWriter(data);
writer.write(cons.toString());
writer.flush();
return true;
} catch (IOException e) {
e.printStackTrace();
return false;
}
}

public static void list(List<?> objs) {
for (Object o : objs) {
System.out.println(o);
}
}

public SimRecorder() {
}

/**
* data.txt 数据存储格式如下:
* tiger,25,3500
* jim,22,3600
* slim,26,5800
*
*/
public static void main(String[] args) {
String datas = "E:\\JProgram\\workhome\\jweb\\simp\\src\\text\\data.txt";
File data = new File(datas);
SimRecorder recorder = new SimRecorder();
List<Worker> workers = recorder.kenWorkers(data);
SimRecorder.list(workers);
Worker worker = new Worker("new added", 25, 5000);
workers.add(worker);
recorder.save(workers, data);
}

}

class Worker {
private String name;
private int age;
private int wage;

public Worker() {
}

public Worker(String name, int age, int wage) {
super();
this.name = name;
this.age = age;
this.wage = wage;
}

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 int getWage() {
return wage;
}

public void setWage(int wage) {
this.wage = wage;
}

public String toString() {
String ws = "**************" + "\nNAME: " + this.getName() + "\nAGE: "
+ this.getAge() + "\nWAGE: " + this.getWage();
return ws;
}
}

Answer 2

用DataInputStream读各种基本数据，这样能读一条记录。
设计一个类，存储单条记录的。
创建一个这个类实例的数组，用循环读，存到这个数组的各元素就可以。
写新记录可以追加到文件末尾。因为磁盘文件系统后移记录开销较大，不值得这么做。