Final answer:
In Java, the correct way to make a copy of an object is either b) using the clone() method for a shallow copy, or d) by creating a new object with the same values for a deep copy. The equals() method is for equality checks, not copying, and setting an object to null is unrelated to copying as well.
Step-by-step explanation:
In Java, you can make a copy of an object primarily using two of the methods you've mentioned.
b) By using the clone() method, you can create a shallow copy of an object. The clone() method is defined in the Object class, and the class of the object being cloned must implement the Cloneable interface to allow the method to perform a shallow copy. However, this method does not copy the objects referenced by the object directly but only the references themselves, which can lead to shared mutable state between the original and the clone.
d) By creating a new object with the same values as the original object, also known as deep copying. This approach involves creating a new instance of the class and then manually copying the properties from the original object to the new one, which ensures that the new object has its own copies of the original object's mutable fields.
Options a) and c) are not methods to create a copy of an object. The equals() method is used to compare objects for equality, and setting an object to null simply makes it eligible for garbage collection and does not involve copying.