java 为什么 <> 运算符不能用于低于 1.7 的源代码？
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Why <> operator is not allowed for source below 1.7?
提问by panipsilos
in a java program , I have the following line of code :
在 java 程序中，我有以下代码行：
HashMap<String, String> query_args = new HashMap<>();
and i receive the following error:
我收到以下错误：
'<>' operator is not allowed for source level below 1.7
低于 1.7 的源代码级别不允许使用“<>”运算符
I tried to change the project compliance and jre to 1.7 but then eclipse could not resolve the imports. I am using jre 1.6.
我试图将项目合规性和 jre 更改为 1.7，但随后 eclipse 无法解析导入。我正在使用 jre 1.6。
Any suggestions?
有什么建议？
回答by Jason
Prior to Java 7 (1.7 here), you needed to do
在 Java 7（此处为 1.7）之前，您需要执行
HashMap<String, String> query_args = new HashMap<String, String>();
Its referred to as the diamond operator, and is not backwards-compatible with earlier versions of Java.
它被称为菱形运算符，并且与早期版本的 Java 不向后兼容。
回答by djechlin
Because that wasn't introduced until Java 7. I really don't know how else to answer that question, besides chronicling the history of Java.
因为它直到 Java 7 才被引入。除了记录 Java 的历史之外，我真的不知道如何回答这个问题。
Regarding imports, you should research why Eclipse cannot resolve whichever imports they are when set to Java 1.7, and if needed post that as a separate question.
关于导入，您应该研究为什么 Eclipse 在设置为 Java 1.7 时无法解析任何导入，如果需要，将其作为单独的问题发布。
