疯狂Java讲义（十二）---- equals

　　eg.

public boolean equals(Object obj) {
    
    if (this == obj) {
        return true;
    }
    
    if (obj != null && obj.getClass() == Person.class) {
        
        Person personObj = (Person)obj;
        if (this.getIdStr().equals(personObj.getIdStr()) {
            return true;
        }
    }

    return false;
}