Java final.docx - The static keyword in java is used for memory management mainly We can apply java static keyword with variables methods blocks and

Java final.docx - The static keyword in java is used for...

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The static keyword in java is used for memory management mainly. We can apply java static keyword with variables, methods, blocks and nested class. The static keyword belongs to the class than instance of the class. The static can be: 1. variable (also known as class variable) 2. method (also known as class method) 3. block 4. nested class Java static variable If you declare any variable as static, it is known static variable. o The static variable can be used to refer the common property of all objects (that is not unique for each object) e.g. company name of employees,college name of students etc. o The static variable gets memory only once in class area at the time of class loading. Advantage of static variable It makes your program memory efficient (i.e it saves memory). Understanding problem without static variable 1. class Student{ 2. int rollno; 3. String name; 4. String college= "ITS" ; 5. } Suppose there are 500 students in my college, now all instance data members will get memory each time when object is created.All student have its unique rollno and name so instance data member is good.Here, college refers to the common property of all objects.If we make it static,this field will get memory only once.
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Java static property is shared to all objects. Example of static variable 1. //Program of static variable 2. 3. class Student8{ 4. int rollno; 5. String name; 6. static String college = "ITS" ; 7. 8. Student8( int r,String n){ 9. rollno = r; 10. name = n; 11. } 12. void display (){System.out.println(rollno+ " " +name+ " " +college);} 13. 14. public static void main(String args[]){ 15. Student8 s1 = new Student8( 111 , "Karan" ); 16. Student8 s2 = new Student8( 222 , "Aryan" ); 17. 18. s1.display(); 19. s2.display(); 20. } 21. } Test it Now Output:111 Karan ITS 222 Aryan ITS
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Program of counter without static variable In this example, we have created an instance variable named count which is incremented in the constructor. Since instance variable gets the memory at the time of object creation, each object will have the copy of the instance variable, if it is incremented, it won't reflect to other objects. So each objects will have the value 1 in the count variable. 1. class Counter{ 2. int count= 0 ; //will get memory when instance is created 3. 4. Counter(){ 5. count++; 6. System.out.println(count); 7. } 8. 9. public static void main(String args[]){ 10. 11. Counter c1= new Counter();
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12. Counter c2= new Counter(); 13. Counter c3= new Counter(); 14. 15. } 16. } Test it Now Output:1 1 1 Program of counter by static variable As we have mentioned above, static variable will get the memory only once, if any object changes the value of the static variable, it will retain its value. 1. class Counter2{ 2. static int count= 0 ; //will get memory only once and retain its value 3. 4. Counter2(){ 5. count++; 6. System.out.println(count); 7. } 8. 9. public static void main(String args[]){ 10. 11. Counter2 c1= new Counter2(); 12. Counter2 c2= new Counter2(); 13. Counter2 c3= new Counter2(); 14.
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