小编Gua*_*ang的帖子

我最近写了下面的代码; 它使用了很多异常处理.我认为它使代码看起来非常难以理解.我可以通过捕获泛型异常来缩短代码,例如

catch (Exception e){
    e.printStackTrace();
}

但我也听说过捕获一般异常不是一个好的编码实践.

public class DataAnalyzerTester {
    /**
     * @param args args[0] stores the filename
     * @exception NoSuchElementException if user attempts to access empty list element
     * @exception ArithmeticException if user attempts to divide by 0
     * @exception ArrayIndexOutOfBoundsException if user supplied less than 3 arguments
     * @exception IOException problems with creating and writing files
     * @exception RuntimeException if user attempts to pass empty list to constructor
     */
    public static void main(String[] args) {

    try{ …

我有以下关系。

Suppliers( sid: integer, sname: string, address: string)
Parts(pid: integer, pname: string, color: string)
Catalog( sid: integer, pid: integer, cost: real)

问题要求我找到 Acme Widget Suppliers 提供的零件的 pnames，而不是其他任何人。我写了下面的SQL语句；但是我觉得这个查询由于重复而效率低下。我想知道是否有更好的方法来编写此查询而不重复选择目录部分。

Select P.pname 
FROM Parts P 
WHERE P.pid IN (
    Select C.pid 
    FROM Catalog C 
    INNER JOIN Supplier S
    ON S.sid = C.sid 
    WHERE S.sname = "Acme Widget Suppliers" 
    AND C.pid NOT IN (
            SELECT C2.pid 
            FROM Catalog C2
            INNER JOIN Supplier S
            ON S.sid = C2.sid 
            WHERE S.sname <> "Acme Widget Suppliers"
        ) …