目录

环境

语法

作用

范例

总结

环境

Java1.7版本及其以后版本

语法

JDK1.7开始，java引入了 try-with-resources 声明，将 try-catch-finally 简化为 try-catch，这其实是一种语法糖，在编译时会进行转化为 try-catch-finally 语句。新的声明包含三部分：try-with-resources 声明、try 块、catch 块。它要求在 try-with-resources 声明中定义的变量实现了 AutoCloseable 接口，这样在系统可以自动调用它们的close方法，从而替代了finally中关闭资源的功能。

作用

关闭在try-catch语句块中使用的资源，需要在ry-with-resources 声明中的实现AutoCloseable 接口的资源。

范例

Java1.7之前写法

public static void main(String[] args) {
    FileInputStream file = null;
    try {
        file = new FileInputStream("D:\\logs\\log-cleaner.log");
        System.out.println("ooo");
        file.read();
        System.out.println("aaa");
    } catch (IOException io) {
        System.out.println("bbb");
        io.printStackTrace();
    } catch (Exception e) {
        System.out.println("ccc");
        e.printStackTrace();
    } finally {
        if (file != null) {
            try {
                file.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

使用 try-with-resources异常处理机制

public static void main(String[] args) {
    try(FileInputStream file = new FileInputStream("D:\\logs\\log-cleaner.log")){
        System.out.println("ooo");
        file.read();
        System.out.println("aaa");
    }catch (IOException io){
        System.out.println("bbb");
        io.printStackTrace();
    }catch (Exception e){
        System.out.println("ccc");
        e.printStackTrace();
    }
}

编译后的class文件，反编译软件jd-gui,下载链接https://download.csdn.net/download/baidu_25310663/10851553

public static void main(String[] paramArrayOfString)
{
    try
    {
        FileInputStream localFileInputStream = new FileInputStream("D:\\logs\\log-cleaner.log"); Object localObject1 = null;
        try { 
            System.out.println("ooo");
            localFileInputStream.read();
            System.out.println("aaa");
        }
        catch (Throwable localThrowable2)
        {
            localObject1 = localThrowable2; throw localThrowable2;
        }
        finally
        {
            if (localFileInputStream != null) if (localObject1 != null) try { localFileInputStream.close(); } catch (Throwable localThrowable3) { localObject1.addSuppressed(localThrowable3); } else localFileInputStream.close();
        }
    } catch (IOException localIOException) {
        System.out.println("bbb");
        localIOException.printStackTrace();
    } catch (Exception localException) {
        System.out.println("ccc");
        localException.printStackTrace();
    }
}

总结

可以增强代码可读性