java expression 强制出现,为什么java编译器不报告Intellij中多播表达式的未经检查的强制转换警告？...

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最新推荐文章于 2023-06-28 15:34:16 发布

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文章标签： java expression 强制出现

本文讨论了在IntelliJ IDEA中使用JDK1.8.0_121时，为何代码没有报告未检查警告的情况。作者提供了一个示例代码，展示了即使存在潜在的类型安全问题，IDEA也不会显示警告。解决方法是在IDE的Java编译器设置中添加`-Xlint:unchecked`选项。当在命令行使用`javac`编译时，也会提示如何启用未检查警告。文章探讨了IDEA与命令行编译器在处理未检查警告方面的行为一致性。

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Why the code below didn't report unchecked warnings by Intellij IDEA with jdk 1.8.0_121 since Supplier & Serializable is the supertype of T?

& Serializable> T createdBy(AtomicInteger counter) {

// v--- if I removed the first cast expression, I can't compile it

return (T) (Supplier & Serializable) counter::incrementAndGet;

// ^--- it should be reports unchecked warnings, but it doesn't

}

And the following code has reported unchecked cast warnings:

R apply(T value) {

return (R) value;

// ^--- unchecked cast

}

Why this question occurs, the interested thing occurs during I write the code at below for chaining a type with multi-supertypes:

AtomicInteger counter = new AtomicInteger(0);

Supplier serialized = serialized(createdBy(counter));

assert serialized.get() == 1; // ok

assert counter.get() == 0 ; // ok

T serialized(T value) {

return deserialize(serialize(value));

}

I have searched through the JLS, but I can't find out the exactly favorable evidence. Could someone tell me why?

解决方案

In IntelliJ IDEA for the java compiler to report unchecked warnings you need to add -Xlint:unchecked option to the Java Compiler | Additional Command line parameters:

If you try to compile it using the command line javac, it will also not report you the warning itself, but will tell how to enable unchecked warnings:

Note: Main.java uses unchecked or unsafe operations.

Note: Recompile with -Xlint:unchecked for details.

The same message is displayed by IntelliJ IDEA if this option is not specified: