MODIFIERS IN JAVA

What Is Modifier ?

Modifiers are keywords that you add to those definitions to change their meanings. A modifier is a keyword that is placed before class, method or variable declaration that changes how it behaves.

In the Java programming language the following keywords are modifiers: abstract, final, native, private, protected, public, static, strictfp, synchronized, transient, and volatile.

The Java language has a wide variety of modifiers, including the following:

Java Access Modifiers

Non Access Modifiers

Java Access Modifiers

Access modifiers specifies who can access them. There are three access modifiers and four access levels in java.

public
private
protected
no modifer i.e default

Class level access modifiers (java classes only)

Only two access modifiers is allowed, public and no modifier i.e default

If a class is public, then it can be accessed from all places.
If a class has no modifer, then it can only be accessed from same package.

Member level access modifiers (java variables and java methods)

Access Modifiers	Same Class	Same Package	Subclass	Other packages
public	Y	Y	Y	Y
protected	Y	Y	Y	N
no access modifier	Y	Y	N	N
private	Y	N	N	N

Non Access Modifiers

Final
Abstract
Static
Strictfp
Native
Synchronized
Transient

Points To Remember

a method declaration can contain only one of the access modifiers public, protected and private
classes cannot be declared abstract and final simultaneously
abstract methods cannot be declared private, static, final, native, strictfp or synchronized
methods cannot be declared native and strictfp simultaneously
abstract and native methods have no body
abstract void method();
native void method();
a class that contains abstract method(s) must be declared abstract
final fields cannot be volatile

Java Modifier


Modifier	Used on	Meaning
abstract	class interface method	Contains unimplemented methods and cannot be instantiated. All interfaces are abstract. Optional in declarations No body, only signature. The enclosing class is abstract
final	class method field variable	Cannot be subclassed Cannot be overridden and dynamically looked up Cannot change its value. static final fields are compile-time constants. Cannot change its value.
native	method	Platform-dependent. No body, only signature
none(package)	class interface member	Accessible only in its package Accessible only in its package Accessible only in its package
private	member	Accessible only in its class(which defins it).
protected	member	Accessible only within its package and its subclasses
public	class interface member	Accessible anywhere Accessible anywhere Accessible anywhere its class is.
strictfp	class method	All methods in the class are implicitly strictfp. All floating-point computation done is strictly conforms to the IEEE 754 standard. All values including intermediate results must be expressed as IEEE float or double values. It is rarely used.
static	class method field initializer	Make an inner class top-level class A class method, invoked through the class name. A class field, invoked through the class name one instance, regardless of class instances created. Run when the class is loaded, rather than when an instance is created.
synchronized	method	For a static method, a lock for the class is acquired before executing the method. For a non-static method, a lock for the specific object instance is acquired.
transient	field	Not be serialized with the object, used with object serializations.
volatile	field	Accessible by unsynchronized threads, very rarely used.