[英]In Java, what is the right way to close variables in a method that throws exceptions?
在Java中,我经常在finally
块中关闭变量,如下所示:
public void someMethod(){
InputStream inStream = null;
PreparedStatement pStatement = null;
try{ do something here }
catch(Exception ex){ do something here }
finally{
try{ if (inStream != null) inStream.close(); } catch(Exception ex){/* do nothing */}
try{ if (pStatement != null) pStatement.close(); } catch(Exception ex){/* do nothing */}
}
}
我想知道,如果该方法说它引发了异常,是否有一个像“最终”这样的地方可以关闭该方法的变量? 例如:
public void anotherMethod() throws SQLException {
// This method doesn't need a try/catch because the method throws an exception.
InputStream inStream = null;
PreparedStatement pStatement = null;
// Where can I ensure these variables are closed?
// I would prefer not to have them be global variables.
}
正确的方法实际上是使用Java 7中引入的try-with-resources构造。
public void anotherMethod() throws SQLException {
try (PreparedStatement st = connection.prepareStatement(...)) {
// do things with st
}
}
这样可以确保在try
块中发生的任何事情(成功执行或以异常结束)都会关闭资源。 您无需添加catch
部分,因为该方法会引发SQLException
,更重要的是,您无需添加finally
子句:保证所有已打开的资源在该语句之后都将被关闭。
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