java - FindBugs 有争议的描述

Question

是我理解错了，还是描述有误？

Equals checks for noncompatible operand (EQ_CHECK_FOR_OPERAND_NOT_COMPATIBLE_WITH_THIS)

This equals method is checking to see if the argument is some incompatible type (i.e., a class that is neither a supertype nor subtype of the class that defines the equals method). For example, the Foo class might have an equals method that looks like:

public boolean equals(Object o) {
  if (o instanceof Foo)
    return name.equals(((Foo)o).name);
  else if (o instanceof String)
    return name.equals(o);
  else return false;

This is considered bad practice, as it makes it very hard to implement an equals method that is symmetric and transitive. Without those properties, very unexpected behavoirs are possible.

发件人:http://findbugs.sourceforge.net/bugDescriptions.html#EQ_CHECK_FOR_OPERAND_NOT_COMPATIBLE_WITH_THIS

描述说 Foo 类可能有一个类似的 equals 方法，然后说“这被认为是不好的做法”。我没有得到“正确的方法”..

下面的方法应该怎样才对？

@Override
public boolean equals(Object obj) {
if (obj instanceof DefaultTableModel)
    return model.equals((DefaultTableModel)obj);
else
    return false;
}

Answer 1

当 FindBugs 描述说某某“可能是这种情况”时，他们并不是在说这是一种可接受的做法，而是说这是一种假设情况，会导致出现相关警告。

您不应该说您的对象等于某个 DefaultTableModel，因为没有办法强制该关系的自反性。这意味着给定

DefaultTableModel dtm = new DefaultTableModel(...);
YourObject foo = new YourObject(dtm);
foo.equals(dtm); // true
dtm.equals(foo); // false!