Working with interfaces and Abstract Classes

Points to note while declaring vars in interface:

1) Variables declared in an interface are public static and final and are initialized before use

Ex:
public interface Bag {

int i=90; //Fine and i is static final variable

//private int k=90; Gives u an error as the variable cant be private.

public String simpleBag();

}

2) Which means u can just references these vars in ur impl classes but u cannot assign them a new value

Abstract Class:

1) You can define private variables in abstract class. They juts behave as variables declared in any other class.

Some code Examples:

public abstract class Badge {
int badgeId=100;
public int getBadgeId() {
return badgeId;
}

public void setBadgeId(int badgeId) {
this.badgeId = badgeId;
}

}


Implementation Class:

public class JPMCBadge extends Badge {

int badgeId=200;
public void showBadge(){
System.out.println(this.badgeId);
//this.badgeId=200;
}
public void newMethodInJpmcBadge(){

System.out.println("This is a new Method in JPMC Badge");

}

}


Main Class:

public class BadgeMain {

public static void main(String[] args) {

Badge badge=new JPMCBadge();

System.out.println(badge.badgeId); //This would print out 100 as we are still referring to badge

JPMCBadge badge2=new JPMCBadge();

badge2.newMethodInJpmcBadge();

System.out.println(badge2.badgeId); //this prints 200

}

}