[Java基础]复制文件的异常处理try...catch...finally的做法

Posted 2021-06-26 Wecccccccc

代码如下:

package ErrorOperatorPack;

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class CopyFileDemo01 {
    public static void main(String[] args)
    {

    }
        private static void method() {
            FileReader fr = null;
            FileWriter fw = null;
        try {
          fr = new FileReader("fr.txt");
             fw = new FileWriter("fw.txt");

            char[] chs = new char[1024];
            int len;
            while((len = fr.read())!=-1)
            {
                fw.write(chs,0,len);
            }
        }catch (IOException e)
        {
            e.printStackTrace();
        }finally {
            if (fr!=null)
            try {
                fr.close();
            }catch (IOException e)
            {
                e.printStackTrace();
            }
            if (fw!=null)
            {
                try{
                    fw.close();
                }catch (IOException e)
                {
                    e.printStackTrace();
                }
            }
        }
        }

}

代码如下:

package ErrorOperatorPack;

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class CopyFileDemo02 {
    public static void main(String[] args)
    {
        
    }
    
    private static void method()
    {
        try(FileReader fr = new FileReader("fr.txt");
            FileWriter fw = new FileWriter("fw.txt");)   
        {
            char[] chs = new char[1024];
            int len;
            while((len = fr.read())!=-1)
            {
                fw.write(chs,0,len);
            }
        }catch (IOException e)
        {
            e.printStackTrace();
        }
    }
    
}

代码如下:

package ErrorOperatorPack;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class CopyFileDemo03 {
    public static void main(String[] args)
    {

    }

    private static void method() throws IOException {
        FileReader fr = new FileReader("fr.txt");
        FileWriter fw = new FileWriter("fw.txt");
        try(fr;fw)
        {
            char[] chs = new char[1024];
            int len;
            while((len = fr.read())!=-1)
            {
                fw.write(chs,0,len);
            }
        }catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}