関連ワード:  what is equal method in java    what is equals function in java    what is hashcode and equals method in java    what is equals method in object class java    what is the use of equals method in java    what equals method does in java    what is use of hashcode and equals method in java    what is contract between hashcode and equals method in java    what is the return type of equals method in java    what is the need for overriding equals () method in java