什么是 Java 中 try catch 中的圆括号/括号()

据我所知，我们使用 try catch如下:

try {
//Some code that may generate exception
}
catch(Exception ex) {
}
//handle exception
finally {
//close any open resources etc.
}

但是我发现了一个密码

try(
ByteArrayOutputStream byteArrayStreamResponse  = new ByteArrayOutputStream();
HSLFSlideShow   pptSlideShow = new HSLFSlideShow(
new HSLFSlideShowImpl(
Thread.currentThread().getContextClassLoader()
.getResourceAsStream(Constants.PPT_TEMPLATE_FILE_NAME)
));
){
}
catch (Exception ex) {
//handel exception
}
finally {
//close any open resource
}

我不能理解为什么这个括号 ()刚刚尝试。

它的用法是什么? 它在 Java 1.7中是新的吗? 我可以在那里编写什么样的语法？

也请给我介绍一些 API 文件。

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最佳答案

It is try with Resources syntax which is new in java 1.7. It is used to declare all resources which can be closed. Here is the link to official documentation. https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

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. The declaration statement appears within parentheses immediately after the try keyword. The class BufferedReader, in Java SE 7 and later, implements the interface java.lang.AutoCloseable. 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).