JavaSE-19.1.4【复制文件的异常处理】

package day10.lesson1.p4;

import java.io.*;

/*
1.4 复制文件的异常处理
 */
public class CopyFileDemo {
    public static void main(String[] args) {

    }


    //抛出处理
    private static void method1() throws IOException {
        FileReader fr = new FileReader("fr.txt");
        FileWriter fw = new FileWriter("fw.txt");

        char[] chars = new char[1024];
        int len;
        while ((len=fr.read(chars)) != -1){
            fw.write(chars, 0, len);
        }

        fw.close();
        fr.close();
    }


    //try-catch-finally处理
    private static void method2() {
        FileReader fr = null;
        FileWriter fw = null;
        try {
            fr = new FileReader("fr.txt");
            fw = new FileWriter("fw.txt");

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


    //JDK7改进处理方案
    private static void method3() {
        try(FileReader fr = new FileReader("fr.txt");
            FileWriter fw = new FileWriter("fw.txt")
            ){
            char[] chars = new char[1024];
            int len;
            while ((len=fr.read(chars)) != -1){
                fw.write(chars, 0, len);
            }
        }catch (IOException e){
            e.printStackTrace();
        }
        //JDK7：try(){}catch(){}会自动释放资源
        //相比于JDK9处理方案，这种好一点，值得推荐
    }


    //JDK9改进处理方案
    /*private static void method4() throws IOException{ //对于下两行需要抛出异常
        FileReader fr = new FileReader("fr.txt");
        FileWriter fw = new FileWriter("fw.txt");

        try(fr;fw){
            char[] chars = new char[1024];
            int len;
            while ((len=fr.read(chars)) != -1){
                fw.write(chars, 0, len);
            }
        }catch (IOException e){
            e.printStackTrace();
        }
        //JDK9：try(){}catch(){}会自动释放资源
        //本地环境JKD8，编译时IDEA报错
    }*/


}