A Guide to Java Initialization | Baeldung

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• Declaration is the process of defining the variable, along with its type and name

• Initialization, on the other hand, is all about assigning a value

• Java primitive types; variables of this type hold their values directly.

• Reference types hold references to objects (instances of classes).

• Unlike primitive types that hold their values in the memory where the variable is allocated, references don’t hold the value of the object they refer to.

• a reference points to an object by storing the memory address where the object is located

• Java doesn’t allow us to discover what the physical memory address is

• objects creation is a bit more complex

• we trigger the initialization using the new keyword

• invokes a constructor and initializes the object in memory

• new keyword is responsible for allocating memory for the new object through a constructor

• the compiler will create a default constructor which has no arguments,

• As soon as we declare these variables, they’re given a default value:

• Instance and class variables don’t require us to initialize them

• Local variables must be initialized before use, as they don’t have a default value and the compiler won’t let us use an uninitialized value

• The final keyword applied to a field means that the field’s value can no longer be changed after initialization

• Constants must be initialized either when they’re declared or in a constructor

• initializer is a block of code that has no associated name or data type and is placed outside of any method, constructor, or another block of code.

• Java offers two types of initializers, static and instance initializers

• the order for initialization statements is as follows: static variables and static initializers in order instance variables and instance initializers in order constructors