Java 复制文件异常处理方案

抛出异常

	private static void method4() throws IOException{
	}

try . . .catch . . .finally 的做法:

	try {
        可能出现异常的代码;
    }catch(异常类名 变量名){
        异常的处理代码;
    }finally{
        执行所有的清除操作;
    }

JDK7改进方案

	try(定义流对象) {
        可能出现异常的代码;
    } catch(异常名 变量名) {
        异常的处理代码;
    }
	
	**自动释放资源**

JDK9 改进方案

	定义输入流对象:
	定义输出流对象:
	try(输入流对象; 输出流对象) {
        可能出现异常的代码;
    }cath(异常类名 变量名) {
        异常的处理代码;
    }

	**自动释放资源**

---

示例代码:

package in.demo09;

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

/*
	异常处理方案
 */

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

    }

    //JDK9的改进方案
    private static void method4() 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();
        }
    }


    //JDK7的改进方案
    private static void method3() {
        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();
        }
    }


    //try . . .catch . . .finally
    private static void method2() {
        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);
            }

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


    //抛出处理
    private static void method1() throws IOException {
        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);
        }

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