The second line of the error message says you are trying to add a JLabel to what the third error line is reporting as a List of JButton objects.

错误消息的第二行表明，您尝试将一个JLabel添加到第三个错误行报告的JButton对象的List。

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Given that, you're left with the third principle of error handling: error handling is informative.

下面是错误处理的第三个原则：错误处理要有告知性。

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The third production of program lets the parser go past an error, search for a semicolon, and continue afterwards (normally an error would be fatal to the parser).

program 的第三个输出让这个分析程序可以获得错误，从中搜索分号，然后继续执行（通常错误对于解析器来说都是非常严重的）。

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Oakland went ahead in the third on Cano's throwing error at second, then he tied it with an RBI single in the bottom half.

WSJ: Balfour fans Wells, saving A's 5-4 win over Yanks

The Yankees scored five runs in the second and the Black Knights came back with four in the third before giving up two runs in the sixth on a throwing error.

WSJ: Yanks beat Army 10-5 in final preseason tuneup

Ciriaco had an RBI single in the second and Gomes' sacrifice fly tied it at 3 in the sixth after an error by Reynolds at third base.

NPR: Red Sox Rally For 4 In 8th To Beat Indians 7-4