For this, our User class must implement the Cloneable interface: public class User implements Cloneable The next method, cloning, is a way to create an exact copy of an object. In this case, we’re using reflection to find and invoke a constructor of the User class. Here’s an example of creating our User object using reflection: void whenInitializedWithReflection_thenInstanceIsNotNull() Reflection is a mechanism we can use to inspect classes, fields, and methods at run-time. Then the object lives its life, and provides us with access to its methods and fields.įinally, when it’s no longer needed, the garbage collector destroys it. In conclusion, an object is first created from a class, usually using the keyword new. All references pointing to the object are out of scope.The object no longer has any references pointing to it.On the other hand, the garbage collector is a Java program that takes care of automatic memory management by deleting objects that are no longer reachable.įor a Java object to become unreachable, it has to encounter one of the following situations: In fact, the heap represents a large pool of unused memory allocated for our Java application. Unlike other languages where we have to worry about object destruction, Java takes care of obsolete objects through its garbage collector.Īll objects in Java are stored in our program’s heap memory. Now that we’ve learned how to declare and initialize objects, let’s discover what happens to objects when they’re not in use. Let’s add a constructor to our User class: Every constructor that doesn’t call another constructor in the same class has a call to its parent constructor, whether it was written explicitly or inserted by the compiler through super(). If we don’t supply a constructor explicitly, the compiler will create a default constructor which has no arguments, and just allocates memory for the object.Ī class can have many constructors, as long as their parameters lists are different ( overload). The new keyword is responsible for allocating memory for the new object through a constructor.Ī constructor is typically used to initialize instance variables representing the main properties of the created object. Let’s discuss constructors and the new keyword in further detail. This, in return, invokes a constructor and initializes the object in memory. This is because we’re not just adding the value to the field instead, we trigger the initialization using the new keyword. Unlike with primitives, objects creation is a bit more complex.
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