java - 有一个主要的抽象类？

Question

将 main 用于抽象类通常是一种不好的做法，还是由于抽象类能够拥有主体的性质而被允许？

Answer 1

当然，抽象类可以有一个 main 方法，就像任何类都可以有一个 main 方法一样，事实上，这是测试抽象类的一种方法——如果您在 main 方法中创建它的具体实现。抽象类唯一不能做的就是按原样构造它们，而不扩展它们和实现所有抽象方法。

public abstract class Foo {
    public abstract void bar();

    public static void main(String[] args) {
        // anonymous inner class representation
        Foo foo = new Foo() {
            // must implement all abstract methods
            public void bar() {
                System.out.println("bar");
            }
        };
        foo.bar();
    }
}

编辑:VitalyGreck 的要点:

abstract classes are abstract because they don't implement some methods in their body. having bar() implemented inside the main() method (even static) confuses users of your class. Good practice is to make two separate classes, one of them - abstract, another - with implementation and static method enclosed. Or dynamically find the enclosing class (see stackoverflow.com/questions/936684/…) using reflection.

换句话说，仅仅因为它可以完成，并不意味着它应该完成。