1. Java Non Access Modifiers
SCJP/OCJP exam objectives – 1.1,1.3,1.4
By,
Srinivas Reddy.S
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2. Non Access Modifiers
• final
• static
• abstract
• strictfp
• native
• synchronized
• transient
• volatile
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3. final
• final can be applied for classes, methods,
instance variables, local variables.
• A class marked as final cannot be extended.
• A method marked with final cannot be
overridden.
• A primitive data type or an object reference
will not change its value or object when
marked final.
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4. static
public class Ford{
int maxSpeed;
public Ford(int maxSpeed){ Ford f = new Ford(100);
this.maxSpeed = maxSpeed;
}
Ford a = new Ford(200);
public void move(){ Ford e = new Ford(150);
int speed = 0;
while(speed<maxSpeed){
System.out.println(“Racing with speed”+speed);
speed++;
} function
f.move();
} of method
a.move();
public void printCarInfo(){ e.move(); varies from Object
System.out.println(“Car name : Ford“); to object
System.out.println(“ Car weight : 230”);
f.printCarInfo();
System.out.println(“Engine Capacity: 3000cc”);
a.printCarInfo(); Same output
}
e.printCarInfo();
}
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5. static
Virtual Memory
.Class File
Members marked as static belong to the Class file and
not the instances
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6. static
• static can be applied for methods and
variables.
• A method or variable marked as static
belongs to class file.
• A static member should be accessed using
the class name.
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7. Accessing static members
• static members can be accessed using the
class name.
E.g.,
public class Ford{
public static void printCarInfo(){
System.out.println(“Car name : Ford“);
System.out.println(“ Car weight : 230”);
System.out.println(“Engine Capacity: 3000cc”);
}
}
Ford.printCarInfo();
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8. Accessing static members
public class Ford{
public static void printCarInfo(){
System.out.println(“Car name : Ford“);
System.out.println(“ Car weight : 230”);
System.out.println(“Engine Capacity: 3000cc”);
}
}
public class FordShowRoom(){
public class FordShowRoom(){
public void getCarInfo(){
public void getCarInfo(){
Ford f = new Ford();
Ford.printCarInfo();
f.printCarInfo();
}
}
}
}
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9. static - rules
• The static variable and static methods are called
class members.
• A method marked as static can only access other
static methods and variables directly.
• To access the instance variables and methods, a
static method should have an instance on which
the object members should be invoked.
• Any instance can access the static variables and
can change them. But, the changes will reflect
for all the objects.
• Members marked as static can be final
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10. static - example
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11. public static void main(String[] args){ }
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12. abstract
public class Car{
public void move(){
System.out.println(“Moves at max 40 kmph”);
}
}
Benz
Ford
BMW
Ferrari
Toyota
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13. abstract
public abstract class Car{
public abstract void move();
}
public class Ford extends Car{
public void move(){
System.out.println(“Move at 120 kmph”);
}
}
public class Benz extends Car{
public void move(){
System.out.println(“Move at 200 kmph – Comfortably ”);
}
}
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14. abstract - rules
• abstract can be applied for classes and
methods only.
• When a method is marked as abstract – It
should not have implementation.
E.g., public abstract void move();
• Abstract methods should end with ‘;’ and not
with ‘{ }’.
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15. abstract - Rules
• When a method marked as abstract, the
whole class should be marked as abstract.
• A class can be abstract with out any abstract
methods in it.
• We cannot create an instance of abstract
class.
• An abstract method should be overridden in
the subclass or should be marked as abstract.
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16. abstract - rules
• Abstract classes can have concrete(non-
abstract) methods in it.
• Abstract methods cannot be marked as final.
• Abstract classes cannot be marked as final.
• Abstract methods cannot be static.
• Abstract methods cannot be private
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17. abstract - rules
• Cannot create an instance of abstract
class???
– An abstract class can contain abstract methods
which does not have functionality and if we can
create objects, we do not have functionality in
abstract methods.
– So, abstract classes are incomplete and are not
eligible for creating instances.
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18. strictfp
• strictfp can only be declared for methods and
classes.
• When declared, the code inside a class or
method will conform to IEEE754 standard
which makes the methods or classes behave
in a platform independent way regarding the
floating points.
• strictfp cannot be used with abstract.
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19. native
• native modifier can only be applied to
methods.
• A native method will always have platform
dependent code like C.
• A native method should not have the
implementation and should end with ‘;’.
• A native methods implementation is
omitted.
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20. synchronized
• synchronized can only be applied for
methods.
• Any method or block that is synchronized will
only allow one single thread to execute the
code at a given time.
• synchronized can be used with any access
modifier.
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21. transient
• only instance variables can be marked as
transient.
• A variable marked as transient will not be
serialized.
volatile
• volatile can only be applied to instance
variables
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22. Access and non access modifiers -
classes
• public
• default
• abstract
• strictfp
• final
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23. Access and non access modifiers-
variables and members
Methods Instance variables Local variables
public public -
protected protected -
default default -
private private -
static static -
final final final
strictfp - -
native - -
- transient -
synchronized - -
abstract - -
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