[英]In Java, what is the right way to close variables in a method that throws exceptions?
在Java中,我經常在finally
塊中關閉變量,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,如果該方法說它引發了異常,是否有一個像“最終”這樣的地方可以關閉該方法的變量? 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.
}
正確的方法實際上是使用Java 7中引入的try-with-resources構造。
public void anotherMethod() throws SQLException {
try (PreparedStatement st = connection.prepareStatement(...)) {
// do things with st
}
}
這樣可以確保在try
塊中發生的任何事情(成功執行或以異常結束)都會關閉資源。 您無需添加catch
部分,因為該方法會引發SQLException
,更重要的是,您無需添加finally
子句:保證所有已打開的資源在該語句之后都將被關閉。
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