Java 中的 Try-with-resources 和 return 语句
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Try-with-resources and return statements in java
提问by maff
I'm wondering if putting a returnstatement inside a try-with-resourcesblock prevents the resource to be automatically closed.
我想知道在try-with-resources块中放置return语句是否会阻止资源自动关闭。
try(Connection conn = ...) {
return conn.createStatement().execute("...");
}
If I write something like this will the Connectionbe closed? In the Oracle documentation it is stated that:
如果我写这样的东西，连接会被关闭吗？在 Oracle 文档中指出：
The try-with-resources statement ensures that each resource is closed at the end of the statement.
try-with-resources 语句确保每个资源在语句结束时关闭。
What happens if the end of the statement is never reached because of a return statement?
如果由于 return 语句而从未到达语句的末尾会发生什么？
采纳答案by merlin2011
Based on Oracle's tutorial, "[the resource] will be closed regardless of whether the try statement completes normally or abruptly". It defines abruptlyas from an exception.
根据Oracle 的教程，“无论 try 语句是正常完成还是突然完成，[资源] 都将关闭”。它定义abruptly为来自异常。
Returning inside the tryis an example of abrupt completion, as defined by JLS 14.1.
返回内部try是JLS 14.1定义的一个突然完成的例子。
回答by Nurettin Armutcu
The resource will be closed automatically (even with a returnstatement) since it implements the AutoCloseableinterface. Here is an example which outputs "closed successfully":
资源将自动关闭（即使使用return语句），因为它实现了AutoCloseable接口。这是一个输出“成功关闭”的示例：
public class Main {
public static void main(String[] args) {
try (Foobar foobar = new Foobar()) {
return;
} catch (Exception e) {
e.printStackTrace();
}
}
}
class Foobar implements AutoCloseable {
@Override
public void close() throws Exception {
System.out.println("closed successfully");
}
}
