java - 文件(读写)无法正确检测到换行符

Question

我想用Java编写一个程序来检查src是否存在（如果不抛出FileNoot的话）
并将src.txt的内容复制到des.txt
并在开头和结尾处打印两个文件的大小

输出为：

src.txt is in current directory
Before opening files:Size of src.txt:43 Bytes   Size of des.txt:0 Bytes
After closing files:Size of src.txt:43 Bytes    Size of des.txt:0 Bytes

src.txt将其内容写入des.txt后，des应该为43个字节
首先，我想问一下我是否可以通过写省略文件声明

PrintWriter outStream = new PrintWriter(new FileWriter("des.txt")); 

而且如果我需要同时 close()文件和流
其次，我想问一下如何适应以下切换情况（系统独立换行）
为了增加一个换行符，在读完之后。

第三，我想问一下关闭文件时try / catch块的重要性
对于这种类型的问题，我们感到非常抱歉，但是在C语言中，没有错误处理（我认为）close（）肯定可以工作

对于这些类型的问题，我感到很抱歉，但是我是Java的初学者

import java.io.*;
public class Main 
{
    public static void main()throws FileNotFoundException
    {

    File src = new File("src.txt");
    if(src.exists())
        System.out.println("src.txt is in current directory");
    else throw new FileNotFoundException("src.txt is not in current directory");

    BufferedReader inStream = null;
    PrintWriter outStream = null;
    try{
        File des = new File("des.txt");
        inStream = new BufferedReader(new FileReader(src));
        outStream = new PrintWriter(new FileWriter(des));

        System.out.print("Before opening files:Size of src.txt:"+src.length()+" Bytes\t");
        System.out.println("Size of des.txt:"+des.length()+" Bytes");
        int c;
        while((c = inStream.read()) != -1){
            switch(c){
                case ' ': outStream.write('@');
                          break;
                case '\r':
                case '\n':outStream.write('\n');
                          outStream.write('\n');
                          break;
                default:outStream.write(c);
            }
        }
        System.out.print("After closing files:Size of src.txt:"+src.length()+" Bytes\t");
        System.out.println("Size of des.txt:"+des.length()+" Bytes");

    } catch(IOException io) {
        System.out.println("Read/Write Error:"+io.toString());
    } finally {
        try{
                if (inStream != null) {
                inStream.close();
                }

                if (outStream != null) {
                outStream.close();
                }
        } catch (IOException io){
            System.out.println("Error while closing Files:"+io.toString());
        }   
    }
} 
}

Answer 1

第一个问题->我想问一下我是否可以通过写省略文件声明

PrintWriter outStream =新的PrintWriter（新的FileWriter（“ des.txt”））;

是的，您可以做到，因为文件编写器具有以下5种方式

FileWriter(File file)
Constructs a FileWriter object given a File object.
FileWriter(File file, boolean append)
Constructs a FileWriter object given a File object.
FileWriter(FileDescriptor fd)
Constructs a FileWriter object associated with a file descriptor.
FileWriter(String fileName)
Constructs a FileWriter object given a file name.
FileWriter(String fileName, boolean append)
Constructs a FileWriter object given a file name with a boolean indicating whether or not to append the data written.