Question

我正在编写一个程序，该程序使用方法来获取收入的用户输入并输出他们所欠的所得税。

我在第46行有一个错误，即``private double GetTax（double taxable）`GetTax是CS0161 - 并非所有代码路径都返回一个值。

我错过了对GetTax的引用吗？非常感谢您的意见！

Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.Util.getInstance(Util.java:384)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:973)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:918)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2588)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2321)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:832)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:417)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:344)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at dcv.testdb.main(testdb.java:11)
Caused by: java.lang.NullPointerException
    at com.mysql.jdbc.ConnectionImpl.getServerCharacterEncoding(ConnectionImpl.java:3307)
    at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1985)
    at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1911)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1288)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2506)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2539)
    ... 13 more

Answer 1

在GetTax（）方法中，所有return语句都包含在if块中。这意味着，如果没有命中if块，则当前没有返回任何值。因此，编译错误。

解决此问题的最简单方法是转换你的＆lt; = line或你的＆gt;行到最后的return语句行，例如：

private double GetTax(double taxable)
{
    if (taxable <= 9225) return (taxable * 1.1);
    //other cases omitted for brevity
    return (119996.25 + (taxable * 1.396));
}

您可以使用else语句作为返回值的前言，但这不是必需的，而是更多的代码样式选择。

C＃：方法WFA纳税计算器

1 个答案: