Abstract class in Java

import java.util.Scanner;
abstract class Person{
    String name, city;
    Scanner sc=new Scanner(System.in);
}
class Emp extends Person{
    int empcode;
    float bsal;
    void get()
    {
        System.out.println("Enter employee name:");
        name=sc.nextLine();
        System.out.println("Enter city:");
        city=sc.nextLine();
        System.out.print("Enter employee code:");
        empcode=sc.nextInt();
        System.out.print("Enter basic salary:");
        bsal=sc.nextFloat();
    }
    void disp()
    {
        System.out.println("Employee name:"+name);
        System.out.println("City:"+city);
        System.out.println("Employee Code:"+empcode);
        System.out.println("Basic Salary:"+bsal);
    }
}
class Stu extends Person{
    int roll;
    String course;
    void get()
    {
        System.out.println("Enter student name:");
        name=sc.nextLine();
        System.out.println("Enter city:");
        city=sc.nextLine();
        System.out.print("Enter course:");
        course=sc.nextLine();
        System.out.print("Enter roll:");
        roll=sc.nextInt();
    }
    void disp()
    {
        System.out.println("Student name:"+name);
        System.out.println("City:"+city);
        System.out.println("Roll:"+roll);
        System.out.println("Course:"+course);
    }
}
public class Abs{
    public static void main(String args[])
    {
        Emp obj1=new Emp();
        Stu obj2=new Stu();
        obj1.get();
        obj2.get();
        obj1.disp();
        obj2.disp();
    }
}

Factorial by recursion using static method

package Rahul;
import java.util.Scanner;
public class Fact {
    static int fact(int num)
    {
        if(num==0)
            return 1;
        else
            return(num*fact(num-1));
    }
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        System.out.print("Enter number:");
        int n=sc.nextInt();
        System.out.print("Factorial of "+n+"="+Sec.fact(n));
    }
}

Inheritance in Java

import java.io.*;
class Student {
    String n,c,s;
    int r,sem;
    Student(){};
    void get(String name, String cou, String ses, int roll, int seme)
    {
        n=name;
        c=cou;
        s=ses;
        r=roll;
        seme=sem;
    }
    void display(){System.out.println("Name: "+n+"\nCourse: "+c+"\nSession: "+s+"\nRoll: "+r+"\nSemester: "+sem);}
}
class Marks extends Student{
    int m[]=new int[3];
    Marks()
    {
        super();
        m[0]=m[1]=m[2]=0;
    }
    void get(int marks[])
    {
        m[0]=marks[0];
        m[1]=marks[1];
        m[2]=marks[2];
    }
    void display()
    {
        Student:display();
        System.out.println("Makrs:\n"+m[0]+"\t"+"\t"+m[1]+"\t"+m[2]);
    }
}
class Main{
        public static void main(String args[])throws IOException
    {
        InputStreamReader ni=new InputStreamReader(System.in);
        BufferedReader in=new BufferedReader(ni);
        Marks obj1=new Marks();
        System.out.print("Enter Student's name:");
        String name=String.valueOf(in.readLine());
        System.out.print("Enter course:");
        String cou=String.valueOf(in.readLine());
        System.out.print("Enter session:");
        String ses=String.valueOf(in.readLine());
        System.out.print("Enter roll number:");
        int roll=Integer.parseInt(in.readLine());
        System.out.print("Enter semester:");
        int seme=Integer.parseInt(in.readLine());
        obj1.get(name,cou,ses,roll,seme);
        System.out.print("Enter marks of three subjects:");
        int marks[]=new int[3];
        marks[0]=Integer.parseInt(in.readLine());
        marks[1]=Integer.parseInt(in.readLine());
        marks[2]=Integer.parseInt(in.readLine());
        obj1.get(marks);
        obj1.display();
    }
}