Why instantiate in java

There 2 categories of nested classes. To instantiate a class means to create an instance of the class. In other words, if you have a class like this:.

Instantiating is when you use the new keyword to actually create an object of your class. Instantiate is creating an instance of a class. I reckon this is not helpful without knowing what an instance is.

You make an instance of this class my calling its constructor and using the keyword new :. An instance of a class is a place in memory that contains the state e. What this means is that, you need to have instantiated that class in order to use the above's example getName method.

After all, it is trying to access the state name of a given object in memory; without that object, there is no state. Instantiate in Java means to call a constructor of a Class which creates an an instance or object, of the type of that Class. Instantiation allocates the initial memory for the object and returns a reference. An instance is required by non-static methods as they may operate on the non-static fields created by the constructor.

Static methods don't need an instance and should not be stateful, i. They are essentially free functions that are associated with the type and not a particular instance. When you want to work with changing data, encapsulating that data as member fields that are operated on by instance methods is the way to go. For example, a Car class might have static numbeOfWheels that always returns 4, but an instance numberOfFlatTires that might return depending on the state of that particular Car.

Inner classes are no different and the only difference between a static and non-static inner class is that the non-static can use the parent instance's members. This can be used to reduce complexity. You might have a looping operation that has a common parameter for the list and an individual parameter for the items. You could use a non-static inner class to encapsulate the operations on the item while referring to the common parameter in the parent class.

Enums are special in that each value is a single instance of a single type that all extend from a common abstract base class defined in the Enum class body. The Enum value is instantiated the first time it's used, but there will only ever be one instance per value. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 4 years, 5 months ago. Active 2 years, 5 months ago.

Viewed 49k times. To instantiate an object in Java, follow these seven steps. Course Catalog. Training Delivery Methods. Live Online Classes. Private Classes. Self-Paced Training. Enterprise Training. All Training Options. Purchase Courseware. Variables of primitive types byte, short, int, long, char, float, double, or boolean always hold a primitive value of that same type. Variables of reference types, however, are slightly more complex.

Remember, variable declaration alone does not actually create an object. For that, you need to use the new operator, as described in the next section. A variable in this state, which currently references no object, is said to hold a null reference. If the code in CreateObjectDemo had declared its originOne variable in this manner, it could be illustrated as follows variable name, plus reference pointing to nothing :. Note: The phrase "instantiating a class" means the same thing as "creating an object"; you can think of the two as being synonymous.

When you create an object, you are creating an instance of a class, therefore "instantiating" a class. The new operator requires a single, postfix argument: a call to a constructor.