blocks|key|2796739|text|它是正确的，并且不需要catch子句。Oracle+java+7文档表示，无论是否真的抛出异常，资源都将被关闭。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2796740|只有当您想要对异常做出反应时，才应该使用catch子句。catch子句将在资源关闭后执行。|2796741|这是来自Oracle's+tutorial的一个片段|2796742|2796743|下面的示例从文件中读取第一行。它使用BufferedReader的一个实例从文件中读取数据。BufferedReader是在程序结束后必须关闭的资源：|blockquote|2796744|2796745|2796746|static+String+readFirstLineFromFile(String+path)+throws+IOException+{
++++try+(BufferedReader+br+=
+++++++++++++++++++new+BufferedReader(new+FileReader(path)))+{
++++++++return+br.readLine();
++++}
}+//+In+this+example,+the+resource+declared+in+the+try-with-resources+statement+is+a+BufferedReader.|code-block|syntax|javascript|2796747|2796748|+...因为BufferedReader实例是在try-with-resource语句中声明的，所以无论try语句是正常完成还是突然完成(由于BufferedReader.readLine方法抛出IOException)，它都将被关闭。|2796749|2796750|2796751|编辑|BOLD|2796752|关于新编辑的问题：|2796753|Java6中的代码先执行catch，然后执行finally块。这会导致资源仍然可能在catch块中打开。|2796754|在Java7语法中，资源在catch块之前关闭，因此资源在catch块执行期间已经关闭。上面的链接记录了这一点：|2796755|2796756|在try-with-resources语句中，任何catch或finally块都是在声明的资源关闭之后运行的。|2796757|2796758|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html^0|B|5|0|K|5|S|5|0|4|H|0|0|0|0|0|0|0|0|0|0|0|0|2|0|0|C|5|M|7|16|5|0|D|5|T|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1K|8|@$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|1S|8|@]|D|@$9|1T|A|1U|1|1V]]|E|$]]|$1|J|3|-4|5|6|7|1W|8|@]|D|@]|E|$]]|$1|K|3|L|5|M|7|1X|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|1Y|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|P|3|Q|5|R|7|20|8|@]|D|@]|E|$S|T]]|$1|U|3|-4|5|6|7|21|8|@]|D|@]|E|$]]|$1|V|3|W|5|M|7|22|8|@]|D|@]|E|$]]|$1|X|3|-4|5|6|7|23|8|@]|D|@]|E|$]]|$1|Y|3|-4|5|6|7|24|8|@]|D|@]|E|$]]|$1|Z|3|10|5|6|7|25|8|@$9|26|A|27|B|11]]|D|@]|E|$]]|$1|12|3|13|5|6|7|28|8|@]|D|@]|E|$]]|$1|14|3|15|5|6|7|29|8|@$9|2A|A|2B|B|C]|$9|2C|A|2D|B|C]|$9|2E|A|2F|B|C]]|D|@]|E|$]]|$1|16|3|17|5|6|7|2G|8|@$9|2H|A|2I|B|C]|$9|2J|A|2K|B|C]]|D|@]|E|$]]|$1|18|3|-4|5|6|7|2L|8|@]|D|@]|E|$]]|$1|19|3|1A|5|M|7|2M|8|@]|D|@]|E|$]]|$1|1B|3|-4|5|6|7|2N|8|@]|D|@]|E|$]]|$1|1C|3|-4|5|6|7|2O|8|@]|D|@]|E|$]]]|1D|$1E|$5|1F|1G|1H|E|$1I|1J]]]]

It's correct and there's no requirement for <code>catch</code> clause. Oracle java 7 doc says the resource will be closed regardless of whether an exception is actually thrown or not.

You should use a <code>catch</code> clause only if you want to react upon the exception. The <code>catch</code> clause will be executed after the resource is closed.

Here's a snippet from <a href="http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html" rel="noreferrer">Oracle's tutorial</a>:

<blockquote>
 The following example reads the first line from a file. It uses an
 instance of BufferedReader to read data from the file. BufferedReader
 is a resource that must be closed after the program is finished with
 it:
</blockquote>

<pre><code>static String readFirstLineFromFile(String path) throws IOException {
 try (BufferedReader br =
 new BufferedReader(new FileReader(path))) {
 return br.readLine();
 }
} // In this example, the resource declared in the try-with-resources statement is a BufferedReader.
</code></pre>

<blockquote>
 ... Because the BufferedReader instance is declared in a
 try-with-resource statement, it will be closed regardless of whether
 the try statement completes normally or abruptly (as a result of the
 method BufferedReader.readLine throwing an IOException).
</blockquote>

EDIT

Regarding the new edited question:

The code in Java 6 executes the <code>catch</code> and afterwards the <code>finally</code> block. This causes the resources to be still potentially opened in the <code>catch</code> block.

In Java 7 syntax, resources are closed before the <code>catch</code> block, so resources are already closed during the <code>catch</code> block execution. This is documented in the above link:

<blockquote>
 In a try-with-resources statement, any catch or finally block is run
 after the resources declared have been closed.
</blockquote>

blocks|key|182548|text|在这种特殊情况下，您使用try-with-resources的用法可以很好地工作，但在一般情况下并不完全正确。你不应该这样链接资源，因为它可能会导致令人不快的惊喜。假设你有一个可变的缓冲区大小：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|182549|public+static+Object[]+fromFile(String+filePath)+throws+FileNotFoundException,+IOException
{
++++int+sz+=+/*+get+buffer+size+somehow+*/
++++try+(BufferedReader+br+=+new+BufferedReader(new+FileReader(filePath),+sz))
++++{
++++++++return+read(br);
++++}+
}|code-block|syntax|javascript|182550|假设出了什么问题，最后你的sz结果是负面的。在这种情况下，您的文件资源(通过new+FileReader(filePath)创建)将被关闭而不是关闭。|offset|length|style|CODE|182551|要避免此问题，应分别指定每个资源，如下所示：|182552|public+static+Object[]+fromFile(String+filePath)+throws+FileNotFoundException,+IOException
{
++++int+sz+=+/*+get+buffer+size+somehow+*/
++++try+(FileReader+file+=+new+FileReader(filePath);
+++++++++BufferedReader+br+=+new+BufferedReader(file,+sz))
++++{
++++++++return+read(br);
++++}+
}|182553|在这种情况下，即使br初始化失败，file仍然会关闭。您可以在here和here上找到更多详细信息。|182554|entityMap|0|LINK|mutability|MUTABLE|url|http://ayp-sd.blogspot.com/2014/01/java-7-try-with-resources-statement.html|1|http://docs.oracle.com/javase/specs/jls/se7/html/jls-14.html#jls-14.20.3^0|0|0|D|2|12|O|0|0|0|9|2|H|4|V|4|0|10|4|1|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|14|8|@$I|15|J|16|K|L]|$I|17|J|18|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|19|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|1B|8|@$I|1C|J|1D|K|L]|$I|1E|J|1F|K|L]]|9|@$I|1G|J|1H|1|1I]|$I|1J|J|1K|1|1L]]|A|$]]|$1|S|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]|10|$5|V|W|X|A|$Y|11]]]]

Your usage of try-with-resources will work fine in this particular case, but it is not quite correct in general. You should not chain resources like that because it may lead to unpleasant surprises. Assume you have a variable buffer size:

<pre><code>public static Object[] fromFile(String filePath) throws FileNotFoundException, IOException
{
 int sz = /* get buffer size somehow */
 try (BufferedReader br = new BufferedReader(new FileReader(filePath), sz))
 {
 return read(br);
 } 
}
</code></pre>

Assume something went wrong and you ended up with <code>sz</code> being negative. In this case your file resource (created via <code>new FileReader(filePath)</code>) will NOT be closed.

To avoid this problem you should specify each resource separately like this:

<pre><code>public static Object[] fromFile(String filePath) throws FileNotFoundException, IOException
{
 int sz = /* get buffer size somehow */
 try (FileReader file = new FileReader(filePath);
 BufferedReader br = new BufferedReader(file, sz))
 {
 return read(br);
 } 
}
</code></pre>

In this case even if initialization of <code>br</code> fails <code>file</code> still gets closed. You can find more details <a href="http://ayp-sd.blogspot.com/2014/01/java-7-try-with-resources-statement.html">here</a> and <a href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-14.html#jls-14.20.3">here</a>.

I am expecting the buffered reader and file reader to close and the resources released if the exception is throw.

<pre><code>public static Object[] fromFile(String filePath) throws FileNotFoundException, IOException
{
 try (BufferedReader br = new BufferedReader(new FileReader(filePath)))
 {
 return read(br);
 } 
}
</code></pre>

However, is there a requirement to have a <code>catch</code> clause for successful closure?

EDIT:

Essentially, is the above code in Java 7 equivalent to the below for Java 6:

<pre><code>public static Object[] fromFile(String filePath) throws FileNotFoundException, IOException
{

 BufferedReader br = null;

 try
 {
 br = new BufferedReader(new FileReader(filePath));

 return read(br);
 }
 catch (Exception ex)
 {
 throw ex;
 }
 finally
 {
 try
 {
 if (br != null) br.close();
 }
 catch(Exception ex)
 {
 }
 }

 return null;
}
</code></pre>

Am I using the Java 7 try-with-resources correctly

Java

如果抛出异常，我期望缓冲的读取器和文件读取器关闭并释放资源。public static Object[] fromFile(String filePath) throws FileNotFoundException, IOException{    try (BufferedReader br = new Buffer...

问我是否正确地使用了Java 7 try-with-resources
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