使用Filewriter将哈希集写入txt [英] Write hashset to txt using filewriter
问题描述
我正在尝试将哈希集写入文本文件.通常,写txt不会有问题,因为这对我来说很简单.但是,在这种情况下,我绝对一无所知.
I am trying to write a hashset to a text file. Normally, I have no issues with writing to txt as it is simple for me. However, in this case I am absolutely clueless.
有关该类的背景知识:它是具有2个字段的ComputerScientist对象的哈希集;名称和研究领域(是的,我知道我填写的哈希集不算什么,我只是想测试一下是否可以使它起作用).
A bit of background about the class: it is a hashset of ComputerScientist objects with 2 fields; name, and field of research (and yes, I know what I put to fill up the hashset does not count, I was only trying to test to see if I could get this to work).
我知道使用文件编写器将字符串保存到哈希集的基本设置,这是我在SO上发现的许多类似问题所解决的问题,因此这些问题并没有真正帮助我.
I know the basic setup to use filewriter to save strings to hashset which is what a lot of the similar questions which I found on SO dealt with, so those did not really help me.
我很想学习,如果您不屑任何粗俗或侮辱性的评论,我将不胜感激.并且,如果已经存在一个类似的问题,涉及将对象的哈希集写入txt文件,我对此表示歉意.
I am eager to learn, and would appreciate it if snide or insulting comments were left out. And if there is already a similar question which deals with writing hashsets of objects to txt file, I apologize for not seeing it.
import java.util.HashSet;
import java.io.FileWriter;
import java.io.IOException;
/**
* Write a description of class ComputerScientistSet here.
*
* @author (your name)
* @version (a version number or a date)
*/
public class ComputerScientistSet
{
private HashSet<ComputerScientist> computerScientistSet;
private FileWriter computerScientistWriter;
private String fileName;
/**
* Constructor for objects of class ComputerScientistSet
*/
public ComputerScientistSet(){
computerScientistSet = new HashSet<ComputerScientist>();
fileName = "scientist-names.txt";
setComputerScientistSet();
}
private void setComputerScientistSet(){
computerScientistSet.add (new ComputerScientist("Bob", "Robotics"));
computerScientistSet.add (new ComputerScientist("Tim", "VR"));
computerScientistSet.add (new ComputerScientist("Jake", "Nuclear Fision"));
computerScientistSet.add (new ComputerScientist("Joe", "Snapple"));
computerScientistSet.add (new ComputerScientist("Jane", "Magnets"));
computerScientistSet.add (new ComputerScientist("Mary", "PC"));
}
public void writeNames(){
try{
computerScientistWriter = new FileWriter(fileName, true);
computerScientistWriter.write(computerScientistSet);
computerScientistWriter.close();
}
catch(IOException ioException){
System.out.println("Error.");
}
}
}
更新: 如果包含以下代码,对您有帮助吗?我仍在计算.write()行括号中的内容.我的大脑炸了:/
Update: Would it help if I include the following code? I am still working out what would go in the parentheses by the .write() line. My brain is fried :/
for (int i = 0; i < computerScientistSet.size(); i++) {
computerScientistWriter.write();
}
推荐答案
由于我假设您要将集合写入文件以供以后读取,因此最好的方法是不要重新发明轮子,而是使用序列化
Since I assume you want to write the set to a file to read it in later, the best way would be not to reinvent the wheel and to use serialization instead.
public class Person implements java.io.Serializable {
private String name;
// constructor, setter, getter, etc
}
public static void main(String[] args) {
Set<Person> persons = new HashSet<Person>();
persons.add(new Person("foo");
try {
FileOutputStream fileOut = new FileOutputStream("/tmp/persons.data");
ObjectOutputStream out = new ObjectOutputStream(fileOut);
out.writeObject(e);
out.close();
fileOut.close();
} catch(IOException e) {
e.printStackTrace();
}
try {
FileInputStream fileIn = new FileInputStream("/tmp/persons.data");
ObjectInputStream in = new ObjectInputStream(fileIn);
Set<Person> persons = (Set<Person>) in.readObject();
in.close();
fileIn.close();
} catch(Exception e) {
e.printStackTrace();
}
}
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