notes.md

Notes (Sep 5, 2022)

Topics

• Static
• IIB
• Final Data member

General Notes

• If a compiler finds an error then there is a code error, if an error is present in JVM(java) there will be an exception.

Static

• Static block
• Static data member
• Static member function

IIB

• IIB - Instance Initialization block.(Data member to be initialised with a specific value.)
• IIB is created before a constructor, before object creation a constructor must be created. (Same applies for default const).
• Only one compound block is allowed for the IIB block.

Final data member

• It is used to create a symbolic constant.
• Final data member --> constant (Data/value can't be changed if a data member is preceded by final).
• Final member function --> Prevents overriding.
• Final class --> No derived

Programs

Program 1: Using IIB Block

/* Java program using IIB block*/
class Student{
	int regno;
	String name;
	{ //IIB
		regno=12003000;
		System.out.println("IIB");
	}
	Student(){
		name ="\0";
		System.out.println("Constructor..");
		regno=14;
	}
}
class StudentDemo{
	public static void main(String args[]){
		Student s=new Student();
		System.out.println("reg.."+s.regno);
	}
}

Output: 
IIB
Constructor..
reg..14

Program 2: Using static

/* Java program using IIB block and static data member*/

class Student{
	int regno;
	String name;
	int m1,m2,m3;
	/*{ //IIB
		regno=12003000;
		System.out.println("IIB");
	}*/
	
	static int count,avg;
	static{
		count=0;avg=0;
		System.out.println("Static block");
	}
	/*static void count(){
		count++;
	}*/
	static void classAvg(){
		System.out.println("class avg.."+ (avg/count));
	}
	Student(int regno,String name,int m1,int m2,int m3){
		this.regno=regno;
		this.name=name;
		this.m1=m1;
		this.m2=m2;
		this.m3=m3;
		avg+=((m1+m2+m3)/3);
		count++;
	}
	void avg(){
		System.out.println(name+":"+(m1+m2+m3)/3);
	}
}
class StudentDemo{
	public static void main(String args[]){
		Student s1=new Student(3001,"xxxx",98,67,56);
		s1.avg();
		Student s2=new Student(3002,"yyyy",88,67,56);
		Student.classAvg();
		s2.avg();
		Student s3=new Student(3003,"zzzz",38,67,56);
		s3.avg();
		Student.classAvg();
		//System.out.println("reg.."+s.regno);
		//System.out.println("Count.."+Student.count);
	}
}

Output:
Static block
xxxx:73
class avg..71
yyyy:70
zzzz:53
class avg..65

Program 3: Final datamember

/* Java program using IIB block and static datamember*/

class Student{
	int regno;
	String name;
	int m1,m2,m3;
	/*{ //IIB
		regno=12003000;
		System.out.println("IIB");
	}*/
	
	static int count=0,avg=0;
	final float PI;
	static{
		count=0;avg=0;
		System.out.println("Static block");
	}
	/*static void count(){
		count++;
	}*/
	static void classAvg(){
		System.out.println("class avg.."+ (avg/count));
	}
	Student(int regno,String name,int m1,int m2,int m3){
		this.regno=regno;
		this.name=name;
		this.m1=m1;
		this.m2=m2;
		this.m3=m3;
		avg+=((m1+m2+m3)/3);
		PI=3.14f;
		count++;
	}
	void avg(){
		System.out.println(name+":"+(m1+m2+m3)/3);
	}
}
class StudentDemo{
	public static void main(String args[]){
		Student s1=new Student(3001,"xxxx",98,67,56);
		s1.avg();
		Student s2=new Student(3002,"yyyy",88,67,56);
		Student.classAvg();
		s2.avg();
		Student s3=new Student(3003,"zzzz",38,67,56);
		s3.avg();
		Student.classAvg();
		//System.out.println("reg.."+s.regno);
		//System.out.println("Count.."+Student.count);
	}
}

Output:
Static block
xxxx:73
class avg..71
yyyy:70
zzzz:53
class avg..65

Programs to try

• Compute array of 3 distances using static data member.