Ex 20: Create an exception class, which throws an exception if operand is nonnumeric in calculating modules. (Use command line arguments).

class NonNum extends Exception
{
NonNum()
{ super("the value is non numeric \n"); }
}
class s06_03
{
public static void main(String ar[])
{
int a,b,c=0;
try
{
a=Integer.parseInt(ar[0]);
throw new NonNum();
}
catch(NumberFormatException e)
{System.out.println(e);}
catch(NonNum e)
{ System.out.println(e);}
}
}

Ex 19: Write a Java program to enable the user to handle any chance of divide by zero exception.

class s06_02
{
public static void main(String ar[])
{
int no=0,m=10,result=0;
try
{
result=m/no;
}
catch(ArithmeticException e)
{
System.out.println(" division by zero ");
System.out.println(" value of result has been set as one");
result=1;
}
catch(Exception e)
{
System.out.println(e);
}
System.out.println("Result :"+result);
}
}

Ex 18: Write a program in Java to display the names and roll numbers of students. Initialize respective array variables for 10 students. Handle Array Index Out Of Bounds Exeption, so that any such problem doesn‟t cause illegal termination of program.

import java.io.*;
class student
{
String name,grade;
int reg,m1,m2,m3;
void read()throws Exception
{
DataInputStream in= new DataInputStream(System.in);
System.out.println("enter the register no : ");
reg=Integer.parseInt(in.readLine());
System.out.println("enter the name : ");
name=in.readLine();
System.out.println("enter mark1 : ");
m1=Integer.parseInt(in.readLine());
System.out.println("enter mark2 : ");
m2=Integer.parseInt(in.readLine());
System.out.println("enter mark3 : ");
m3=Integer.parseInt(in.readLine());
}
public void disp_grade()
{
int tt=m1+m2+m3;
if(tt>=250) grade="A";
else if(tt>=200) grade="B";
else if(tt>=150) grade="C";
else if(tt>=100) grade="D";
else grade="E";
System.out.println("Grade :"+grade);
}
void disp()
{
System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
System.out.println(" MARK LIST OF STUDENTS ");
System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
System.out.println("Register No :"+reg);
System.out.println("Name :"+name);
System.out.println("Mark1 :"+m1);
System.out.println("Mark2 :"+m2);
System.out.println("Mark3 :"+m3);
disp_grade();
}
}
class s06_01
{
public static void main(String ar[])
{
int no=0;
student s=new student();
try
{
DataInputStream in= new DataInputStream(System.in);
System.out.println("enter the number of students : ");
no=Integer.parseInt(in.readLine());
for(int i=0;i<no;i++);
s.read();
}
catch(ArrayIndexOutOfBoundsException e)
{
System.out.println("the maximum students should be ten\n");
no=10;
}
catch(Exception e)
{ System.out.println(e); }
for(int i=0;i<no;i++);
s.disp();
}
}

Ex 16: Create an Interface having two methods division and modules. Create a class, which overrides these methods.

interface course
{
void division(int a);
void modules(int b);
}
class stud implements course
{
String name;
int div,mod;
void name(String n)
{ name=n; }
public void division(int a)
{ div=a; }
public void modules(int b)
{ mod=b; }
void disp()
{
System.out.println("Name :"+name);
System.out.println("Division :"+div);
System.out.println("Modules :"+mod);
}
}
//--------main---------------
class s05_03
{
public static void main(String args[])
{ stud s=new stud();
s.name("Arun");
s.division(5);
s.modules(15);
s.disp();
}
}

Ex 15: Write a program in Java to show the usefulness of Interfaces as a place to keep constant value of the program.

interface area
{
static final float pi=3.142f;
float compute(float x,float y);
}
class rectangle implements area
{
public float compute(float x,float y)
{return(x*y);}
}
class circle implements area
{
public float compute(float x,float y)
{return(pi*x*x);}
}
class s05_02
{
public static void main(String args[])
{
rectangle rect=new rectangle();
circle cr=new circle();
area ar;
ar=rect;
System.out.println("Area of the rectangle= "+ar.compute(10,20));
ar=cr;
System.out.println("Area of the circle= "+ar.compute(10,0));
}
}

Ex 14: Write a program to make a package Balance in which has Account class with Display_Balance method in it. Import Balance package in another program to access Display_Balance method of Account class.

class s05_01
{
public static void main(String ar[])
{
try
{
balance.account a=new balance.account();
a.read();
a.disp();
}
catch(Exception e)
{ System.out.println(e); }
}
}
package balance;
import java.io.*;
public class account
{
long acc,bal;
String name;
public void read()throws Exception
{
DataInputStream in=new DataInputStream(System.in);
System.out.println("Enter the name :");
name=in.readLine();
System.out.println("Enter the account number :");
acc=Long.parseLong(in.readLine());
System.out.println("Enter the account balance :");
bal=Long.parseLong(in.readLine());
}
public void disp()
{
System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
System.out.println("--- Account Details ---");
System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
System.out.println("Name :"+name);
System.out.println("Account number :"+acc);
System.out.println("Balance :"+bal);
}
}

Ex 13: Consider the trunk calls of a telephone exchange. A trunk call can be ordinary, urgent or lightning. The charges depend on the duration and the type of the call. Writ a program using the concept of polymorphism in Java to calculate the charges.

import java.io.*;
class call
{
float dur;
String type;
float rate()
{
if(type.equals("urgent"))
return 4.5f;
else if(type=="lightning")
return 3.5f;
else
return 3f;
}
}
class bill extends call
{
float amount;
DataInputStream in=null;
bill()
{
try
{
in=new DataInputStream(System.in);
}
catch(Exception e)
{ System.out.println(e); }
}
void read()throws Exception
{
String s;
System.out.println("enter call type(urgent,lightning,ordinary):");
type=in.readLine();
System.out.println("enter call duration:");
s=in.readLine();
dur=Float.valueOf(s).floatValue();
}
void calculate()
{
if(dur<=1.5)
amount=rate()*dur+1.5f;
else if(dur<=3)
amount=rate()*dur+2.5f;
else if(dur<=5)
amount=rate()*dur+4.5f;
else
amount=rate()*dur+5f;
}
void print()
{
System.out.println("**********************");
System.out.println(" PHONE BILL ");
System.out.println("**********************");
System.out.println(" Call type : "+type);
System.out.println(" Duration : "+dur);
System.out.println(" CHARGE : "+amount);
System.out.println("**********************");
}
}
class s04_04
{
public static void main(String arg[])throws Exception
{
bill b=new bill();
b.read();
b.calculate();
b.print();
}
}