Java 泛型的乐趣

发布于 2024-08-05 04:52:09 字数 416 浏览 5 评论 0原文

有人知道如何使用泛型编写下面的代码并避免编译器警告吗？（@SuppressWarnings("unchecked") 被认为是作弊）。

并且，也许通过泛型检查“左”的类型与“右”的类型相同？

public void assertLessOrEqual(Comparable left, Comparable right) {
    if (left == null || right == null || (left.compareTo(right) > 0)) {
        String msg = "["+left+"] is not less than ["+right+"]";
        throw new RuntimeException("assertLessOrEqual: " + msg);
    }
}

原文

Anybody knows how to write the piece of code below using generics AND avoiding compiler warnings ? (@SuppressWarnings("unchecked") is considered cheating).

And, maybe, checking via generics that the type of "left" is the same as the type of "right" ?

public void assertLessOrEqual(Comparable left, Comparable right) {
    if (left == null || right == null || (left.compareTo(right) > 0)) {
        String msg = "["+left+"] is not less than ["+right+"]";
        throw new RuntimeException("assertLessOrEqual: " + msg);
    }
}

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烟若柳尘 2024-08-12 04:52:09

这也适用于 Comparable 类型的子类：

public <T extends Comparable<? super T>> void assertLessOrEqual(T left, T right) {
  if (left == null || right == null || left.compareTo(right) > 0) {
    String msg = "["+left+"] is not less than ["+right+"]";
    throw new RuntimeException("assertLessOrEqual: " + msg);
  }
}

This works with subclasses of Comparable types too:

public <T extends Comparable<? super T>> void assertLessOrEqual(T left, T right) {
  if (left == null || right == null || left.compareTo(right) > 0) {
    String msg = "["+left+"] is not less than ["+right+"]";
    throw new RuntimeException("assertLessOrEqual: " + msg);
  }
}

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不回头走下去 2024-08-12 04:52:09

怎么样：

public <T extends Comparable<T>> void assertLessOrEqual(T left, T right) {
  if (left == null || right == null || (left.compareTo(right) > 0)) {
    String msg = "["+left+"] is not less than ["+right+"]";
    throw new RuntimeException("assertLessOrEqual: " + msg);
  }
}

它可能会变得更通用一点，但也只能让它变得更复杂:)

How about this:

public <T extends Comparable<T>> void assertLessOrEqual(T left, T right) {
  if (left == null || right == null || (left.compareTo(right) > 0)) {
    String msg = "["+left+"] is not less than ["+right+"]";
    throw new RuntimeException("assertLessOrEqual: " + msg);
  }
}

It could probably be made a little bit more general, but only by making it more complicated as well :)

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回眸一笑 2024-08-12 04:52:09

您无法通过泛型检查运行时“左”的类型是否与“右”的类型相同。 Java泛型是通过类型擦除实现的，因此有关泛型类型参数的信息在运行时会丢失。

public <T extends Comparable<T>> void assertLessOrEqual(T left, T right) {
    if (left == null || right == null || (left.compareTo(right) > 0)) {
        String msg = "["+left+"] is not less than ["+right+"]";
        throw new RuntimeException("assertLessOrEqual: " + msg);
    }
}

You cannot via generics check if the type of 'left' is the same as the type of 'right' at runtime. Java generics is implemented via type erasure, so that the information about the generic type parameters is lost at runtime.

public <T extends Comparable<T>> void assertLessOrEqual(T left, T right) {
    if (left == null || right == null || (left.compareTo(right) > 0)) {
        String msg = "["+left+"] is not less than ["+right+"]";
        throw new RuntimeException("assertLessOrEqual: " + msg);
    }
}

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~没有更多了~