EQ_SELF_USE_OBJECT 错误

Question

我正在编写一个 equals 方法，其中如果两个名字具有相同的名字、中间名和姓氏，则它们被视为相等。但是，我不断收到错误消息

"This class defines a covariant version of the equals() method, but inherits the normal equals(Object) method defined in the base java.lang.Object class. The class should probably define a boolean equals(Object) method."

当我将其更改为 Object other 作为参数时，出现 "no such method" 错误。

public boolean equals(Name other) {

    boolean sameFirstName = firstName.equals(other.firstName);
    boolean sameMiddleName = middleName.equals(other.middleName);
    boolean sameLastName = lastName.equals(other.lastName);
    if (sameFirstName && sameMiddleName && sameLastName) {
        return true;
    }
    return false;
}

Answer 1

您通过使用不同的参数来键入 Object 来重载方法 equals。以下应该适合您。

@Override
public boolean equals(Object object) {
    if(this == object) return true;
    if(!(object instanceof Name)) return false;

    Name other = (Name) object;
    boolean sameFirstName = firstName.equals(other.firstName);
    boolean sameMiddleName = middleName.equals(other.middleName);
    boolean sameLastName = lastName.equals(other.lastName);
    if (sameFirstName && sameMiddleName && sameLastName) {
        return true;
    }
    return false;
}

Answer 2

您必须为调用 'other' 的参数使用对象类型。然后进行检查和铸造实例。请参考这个answer

如果您使用Java 7或更高版本，您可以使用此代码：

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    Person person = (Person) o;
    return Objects.equals(firstName, person.firstName) &&
           Objects.equals(middleName, person.middleName) &&
           Objects.equals(lastName, person.lastName);
}

并且在IDE中有一个自动生成的等号：

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;

    Person person = (Person) o;

    return !(firstName != null ? !firstName.equals(person.firstName) : person.firstName != null) 
                && !(middleName != null ? !middleName.equals(person.middleName) : person.middleName != null) 
                && !(lastName != null ? !lastName.equals(person.lastName) : person.lastName != null);

}

请注意，还应该进行 NPE 检查。

EQ_SELF_USE_OBJECT 错误

EQ_SELF_USE_OBJECT Bug

java

methods

equals