JDK7和JDK9流中异常的处理

JDK7新特性：

　　在try的后边可以增加一个( )，在括号中可以定义流对象

　　那么这个流对象的作用域就在try中有效，try中的代码执行完毕，会自动把流对象释放，不再需要写finally

package com.fgy.demo;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

// JDK7以前写法
public class Demo04CopyFile {
    public static void main(String[] args) {
        FileInputStream inputStream = null;
        FileOutputStream outputStream = null;
        try {
            inputStream = new FileInputStream("d:\a.txt");
            outputStream = new FileOutputStream("d:\b.txt");
            int len = 0;

            /*while ((len = inputStream.read()) != -1) {
                outputStream.write(len);
            }*/

            byte[] bytes = new byte[1024];
            while ((len = inputStream.read(bytes)) != -1) {
                outputStream.write(bytes, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (outputStream != null) {
                try {
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

package com.fgy.demo;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

// JDK7写法
public class Demo05JDK7 {
    public static void main(String[] args) {
        try (FileInputStream inputStream = new FileInputStream("d:\a.txt");
             FileOutputStream outputStream = new FileOutputStream("d:\c.txt")) {
            int len = 0;
            byte[] bytes = new byte[1024];
            while ((len = inputStream.read(bytes)) != -1) {
                outputStream.write(bytes, 0, len);
            }
        }catch (IOException e) {
            e.printStackTrace();
        }
    }
}

JDK9新特性：

　　try前边可以定义流对象

　　try后边的( )中可以直接引入流对象的名称（变量名）

　　在try代码执行完毕后会自动释放资源，不用写finally

package com.fgy.demo;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

// JDK9写法
public class Demo05JDK9 {
    public static void main(String[] args) throws FileNotFoundException {
        FileInputStream inputStream = new FileInputStream("d:\a.txt");
        FileOutputStream outputStream = new FileOutputStream("d:\d.txt");
        try (inputStream; outputStream) {
            int len = 0;
            byte[] bytes = new byte[1024];
            while ((len = inputStream.read(bytes)) != -1) {
                outputStream.write(bytes, 0, len);
            }
        }catch (IOException e) {
            e.printStackTrace();
        }
    }
}