JAVA PROGRAMMING LAB
R-20 Syllabus for CSE, JNTUK w. e. f. 2020 – 21
Exercise - 1 (Basics)
a) Write a JAVA program to display default value of all primitive data type of JAVA
b) Write a java program that display the roots of a quadratic equation ax2+bx=0. Calculate the discriminate D and basing on value of D, describe the nature of root.
c) Five Bikers Compete in a race such that they drive at a constant speed which may or may not be the same as the other. To qualify the race, the speed of a racer must be more than the average speed of all 5 racers. Take as input the speed of each racer and print back the speed of qualifying racers.
Exercise - 2 (Operations, Expressions, Control-flow, Strings)
a) Write a JAVA program to search for an element in a given list of elements using binary search mechanism.
b) Write a JAVA program to sort for an element in a given list of elements using bubble sort
c) Write a JAVA program to sort for an element in a given list of elements using merge sort.
d) Write a JAVA program using StringBuffer to delete, remove character.
Exercise - 3 (Class, Objects)
a) Write a JAVA program to implement class mechanism. Create a class, methods and invoke them inside main method.
b) Write a JAVA program to implement constructor.
Exercise - 4 (Methods)
a) Write a JAVA program to implement constructor overloading.
b) Write a JAVA program implement method overloading.
Exercise - 5 (Inheritance)
a) Write a JAVA program to implement Single Inheritance
b) Write a JAVA program to implement multi level Inheritance
c) Write a java program for abstract class to find areas of different shapes
Exercise - 6 (Inheritance - Continued)
a) Write a JAVA program give example for “super” keyword.
b) Write a JAVA program to implement Interface. What kind of Inheritance can be achieved?
Exercise - 7 (Exception)
a) Write a JAVA program that describes exception handling mechanism
b) Write a JAVA program Illustrating Multiple catch clauses
Exercise – 8 (Runtime Polymorphism)
a) Write a JAVA program that implements Runtime polymorphism
b) Write a Case study on run time polymorphism, inheritance that implements in above problem
Exercise – 9 (User defined Exception)
a) Write a JAVA program for creation of Illustrating throw b) Write a JAVA program for creation of Illustrating finally c) Write a JAVA program for creation of Java Built-in Exceptions d) d)Write a JAVA program for creation of User Defined Exception
Exercise – 10 (Threads)
a) Write a JAVA program that creates threads by extending Thread class .First thread display “Good Morning “every 1 sec, the second thread displays “Hello “every 2 seconds and the third display “Welcome” every 3 seconds ,(Repeat the same by implementing Runnable)
b) Write a program illustrating isAlive and join ()
c) Write a Program illustrating Daemon Threads.
Exercise - 11 (Threads continuity)
a) Write a JAVA program Producer Consumer Problem
b) Write a case study on thread Synchronization after solving the above producer consumer problem
Exercise – 12 (Packages)
a) Write a JAVA program illustrate class path
b) Write a case study on including in class path in your os environment of your package.
c) Write a JAVA program that import and use the defined your package in the previous Problem
Exercise - 13 (Applet)
a) Write a JAVA program to paint like paint brush in applet.
b) Write a JAVA program to display analog clock using Applet. c) Write a JAVA program to create different shapes and fill colors using Applet.
Exercise - 14 (Event Handling)
a) Write a JAVA program that display the x and y position of the cursor movement using Mouse.
b) Write a JAVA program that identifies key-up key-down event user entering text in a Applet.
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Lab solutions
Exercise - 1 (Basics)
a). Write a JAVA program to display default value of all primitive data type of JAVA
import java.io.*;
class Primitivevalues
{
static boolean B1;
static byte T1;
static int I1;
static float F1;
static double D1;
static char C1;
public static void main(String args[])
{
System.out.println("static variable Default values for BYTE:"+T1);
System.out.println("static variable Default values for INT:"+I1);
System.out.println("static variable Default values for FLOAT:"+F1);
System.out.println("static variable Default values for DOUBLE:"+D1);
System.out.println("static variable Default values for CHAR:"+C1);
System.out.println("static variable Default values for BOOLEAN:"+B1);
}
}
b). Write a java program that display the roots of a quadratic equation ax2+bx=0. Calculate
the discriminate D and basing on value of D, describe the nature of root.
import java.io.*;
import static java.lang.Math.sqrt;
import java.util.*;
class Roots
{
void m1(int a,int b,int c)
{
double value=(Math.pow(b,2.0)-4*a*c);
double discriminant=(double)Math.sqrt(value);
if(value>0)
{
System.out.println("Roots are real numbers");
double root1=(discriminant-b)/(2*a);
double root2=(-b-discriminant)/(2*a);
System.out.println("FirstRoot"+root1+"\nSecond Root"+root2);
}
else if(value==0)
{
double root1=(discriminant-b)/(2*a);
System.out.println("Polynomial has one Root"+root1);
}
if(value<0)
{
System.out.println("Roots are imaginary numbers");
System.out.println((-b+"i"+"+"+(-1*value))+"/"+(2*a));
System.out.println((-b+"i"+"-"+(-1*value))+"/"+(2*a));
}
}
public static void main(String [] args)
{
int a,b,c;
System.out.print("Enter a,b,c values:");
Scanner br=new Scanner(System.in);
a=br.nextInt();
b=br.nextInt();
c=br.nextInt();
new Roots().m1(a,b,c);
}
}
c). Five Bikers Compete in a race such that they drive at a constant speed which may or may
not be the same as the other. To qualify the race, the speed of a racer must be more than the
average speed of all 5 racers. Take as input the speed of each racer and print back the speed
of qualifying racers.
import java.io.*;
import java.util.*;
class Race
{
public static void main(String [] args)
{
int R[]=new int[20];
float avg;
int sum=0;
System.out.println("Enter Speed of 5 members");
Scanner sc=new Scanner(System.in);
for(int j=1;j<=5;j++)
{
R[j]=sc.nextInt();
sum+=R[j];
}
avg=sum/5;
for(int i=1;i<=5;i++)
{
if(avg<R[i])
{
System.out.println("QualifiedRaceris:"+i+"with value="+R[i]);
}
}
}
}
Exercise - 2 (Operations, Expressions, Control-flow, Strings)
a). Write a JAVA program to search for an element in a given list of elements using binary
search mechanism.
import java.util.Scanner;
import java.io.*;
class Binarys
{
public static void main(String args[])
{
int c,first,last,middle,n,search,array[];
boolean status=false;
Scanner s=new Scanner(System.in);
System.out.println("Enter number of elements:");
n=s.nextInt();
array=new int[n];
System.out.println("Enter"+n+"integer:");
for(c=0;c<n;c++)
array[c]=s.nextInt();
for (int i = 0; i < array.length; i++)
{
for (int j = i + 1; j < array.length; j++)
{
if (array[i] > array[j])
{
int temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}
System.out.println("Enter value to find:");
search=s.nextInt();
first=0;
last=n-1;
middle=(first+last)/2;
for(int i=0;i<n;i++)
{
if(first<=last)
{
if(array[middle]<search)
first=middle+1;
else if(array[middle]==search)
{
status=true;
}
else
{
last=middle-1;
}
middle=(first+last)/2;
}
}
if(status==true)
{
System.out.println(search+"found at location"+(middle+1));
}
else
System.out.println(search+"is not found in the list");
}
}
b). Write a JAVA program to sort for an element in a given list of elements using bubble sort.
import java.util.Scanner;
public class Bubblesort
{
public static void main(String[] args)
{
Scanner s=new Scanner(System.in);
System.out.println("enter the size of the array:");
int size=s.nextInt();
System.out.println("enter the values into the array:");
int arr[]=new int[size];
for(int i=0;i<size;i++)
{
arr[i]=s.nextInt();
}
sorting(arr);
}
public static void sorting(int arr[])
{
int n=arr.length;
int temp=0;
for(int i=0;i<n;i++)
{
for(int j=1;j<(n-i);j++)
{
if(arr[j-1]>arr[j])
{
temp=arr[j-1];
arr[j-1]=arr[j];
arr[j]=temp;
}
}
}
System.out.println("the sorted arraty is:");
for(int i=0;i<arr.length;i++)
{
System.out.print(arr[i]+"\t");
}
}
}
(c). Write a JAVA program to sort for an element in a given list of elements using merge sort.
import java.util.Scanner;
class merge
{
public static void main(String args[])
{
Scanner s=new Scanner(System.in);
System.out.println("enter size of the array:");
int size=s.nextInt();
int arr[]=new int[size];
System.out.println("enter elements into the array:");
for(int i=0;i<size;i++)
{
arr[i]=s.nextInt();
}
int start=0;
int end=size-1;
sort(arr,start,end);
System.out.println("the sorted array is:");
for(int j=0;j<size;j++)
{
System.out.print(arr[j]+"\t");
}
}
public static void sort(int arr[],int start,int end)
{
if(start<end)
{
int middle=(start+end)/2;
sort(arr,start,middle);
sort(arr,middle+1,end);
merge(arr,start,middle,end);
}
}
public static void merge(int arr[],int start,int middle,int end)
{
int n1 = middle -start + 1;
int n2 = end - middle;
int L[] = new int [n1];
int R[] = new int [n2];
for (int i=0; i<n1; ++i)
{
L[i] = arr[start + i];
}
for (int j=0; j<n2; ++j)
{
R[j] = arr[middle + 1+ j];
}
int i = 0, j = 0;
int k = start;
while (i < n1 && j < n2)
{
if (L[i] <= R[j])
{
arr[k] = L[i];
i++;
}
else
{
arr[k] = R[j];
j++;
}
k++;
}
while (i < n1)
{
arr[k] = L[i];
i++;
k++;
}
while (j < n2)
{
arr[k] = R[j];
j++;
k++;
}
}
}
(d) Write a JAVA program using StringBufferto delete, remove character.
import java.util.Scanner;
import java.lang.*;
class stringbuffer
{
public static void main(String args[])
{
Scanner s=new Scanner(System.in);
System.out.println("enter a string you like:");
String str=s.nextLine();
StringBuffer b=new StringBuffer(str);
System.out.println("enter the index you want to delete from:");
int i1=s.nextInt();
System.out.println("to:");
int i2=s.nextInt();
b.delete(i1,i2);
System.out.println("after deletion the new buffer is:"+b);
}
}
Exercise - 3 (Class, Objects)
a). Write a JAVA program to implement class mechanism. – Create a class, methods and
invoke them inside main method.
import static java.lang.System.*;
class Student{
int rno=420;
String name="Raju";
String _class="CSE-2";
public void display() {
out.println(name);
out.println(rno);
out.println(_class);
}
}
public class Details {
public static void main(String[] args) {
Student s=new Student();
s.display();
}
}
a). Write a JAVA program to implement constructor overloading.
class Student{
int sno;
String sname;
float fee;
public Student()
{
}
public Student(int sn,String snm,float f)
{
sno=sn;
sname=snm;
fee=f;
}
public void display()
{
System.out.println("Sno : "+sno);
System.out.println("Sname : "+sname);
System.out.println("Fees : "+fee);
}
}
public class ConsOvl {
public static void main(String[] args) {
// overloading zero arg constructor
Student s=new Student();
s.display();
//overloading parameterized constructor
Student s1=new Student(100, "Raj",500);
s1.display();
//anonymous object
new Student().display();
}
}
output:
Sno : 0
Sname : null
Fees : 0.0
Sno : 100
Sname : Raj
Fees : 500.0
Sno : 0
Sname : null
Fees : 0.0
b). Write a JAVA program implement method overloading.
package Ovltest;
class Student{
int sno;
String sname;
float fee;
public void getData()
{
}
public void getData(int sn,String snm,float f)
{
sno=sn;
sname=snm;
fee=f;
}
public void display()
{
System.out.println("Sno : "+sno);
System.out.println("Sname : "+sname);
System.out.println("Fees : "+fee);
}
}
public class MethodOvl {
public static void main(String[] args) {
Student s=new Student();
s.getData();
s.display();
Student s1=new Student();
s1.getData(101,"babe",500);
s1.display();
}
}
output:
Sno : 0
Sname : null
Fees : 0.0
Sno : 101
Sname : babe
Fees : 500.0
Exercise - 5 (Inheritance)
a). Write a JAVA program to implement Single Inheritance
import java.util.Scanner;
class Add
{
protected int a,b,sum;
void add()
{
Scanner s=new Scanner(System.in);
System.out.println("Enter two values");
a=s.nextInt();
b=s.nextInt();
sum=a+b;
System.out.println("The sum of the given numbers is:"+sum);
}
}
class Mul extends Add
{
int mul;
void mul()
{
mul=a*b;
System.out.println("The product of the given numbers is:"+mul);
}
}
class Calculation
{
public static void main(String args[])
{
Mul m=new Mul();
m.add();
m.mul();
}
}
b). Write a JAVA program to implement multi level Inheritance
import java.util.Scanner;
class calculator
{
public static void main(String args[])
{
System.out.println("Enter the values:");
Scanner s=new Scanner(System.in);
int a=s.nextInt();
int b=s.nextInt();
Product pr=new Product();
pr.Addition(a,b);
pr.Substraction();
pr.Mul();
}
}
class Add
{
protected int p,q;
public void Addition(int x,int y)
{
p=x;
q=y;
int r=p+q;
System.out.println("Inside of the class 'Addition' ......");
System.out.println("The sum is:"+r);
}
}
class Sub extends Add
{
int diff;
public void Substraction()
{
int diff=p-q;
System.out.println("Inside of the class Sub.........");
System.out.println("Difference is:"+diff);
}
}
class Product extends Sub
{
int prod;
public void Mul()
{
int prod=p*q;
System.out.println("Inside of the class Product.......");
System.out.println("Product is:"+prod);
}
}
c). Write a java program for abstract class to find areas of different shapes
import java.util.Scanner;
abstract class Areas
{
public void display()
{
System.out.println("Inside of the abstract class....");
}
abstract void area();
}
class Rectangle extends Areas
{
int base=10;
int height=20;
public void area()
{
int area=base*height;
System.out.println("Area of the rectangle is:"+area);
}
}
class Square extends Areas
{
int base=15;
public void area()
{
int area1=base*base;
System.out.println("Area of the Square is:"+area1);
}
}
class Triangle extends Areas
{
int base=5;
int height=15;
public void area()
{
int area2=(base*height)/2;
System.out.println("Area of the Triangle is:"+area2);
}
}
class Geometry
{
public static void main(String args[])
{
Rectangle r=new Rectangle();
Square s=new Square();
Triangle t=new Triangle();
r.display();
r.area();
s.area();
t.area();
}
}
Exercise - 6 (Inheritance - Continued)
a). Write a JAVA program give example for “super” keyword.
//Write a program to implement 'super' keyword
class One
{
protected int a;
One(int i)
{
this.a=i;
}
void display()
{
System.out.println("Super class method:a="+a);
}
}
class Two extends One
{
protected int a;
Two(int i,int j)
{
super(i);
a=j;
}
void display()
{
super.display();
System.out.println("Sub class method:a="+a);
}
}
class Super1
{
public static void main(String args[])
{
Two t=new Two(9,6);
t.display();
}
}
b). Write a JAVA program to implement Interface. What kind of Inheritance can be achieved?
import java.util.Scanner;
interface Base1
{
final double pie=3.14;
void area();
}
class Base2
{
protected int r;
public void getdata()
{
Scanner s=new Scanner(System.in);
System.out.print("Enter the radius of the Circle:");
r=s.nextInt();
}
}
class Derived extends Base2 implements Base1
{
double area;
public void area()
{
area=pie*r*r;
System.out.println("Area of the Circle is:"+area);
}
}
class Inheritance
{
public static void main(String args[])
{
Derived d=new Derived();
d.getdata();
d.area();
}
}
Multiple inheritance is achieved through interfaces
Exercise - 7 (Exception)
a).Write a JAVA program that describes exception handling mechanism
import java.util.Scanner;
class Exception_handle
{
public static void main(String args[])
{
Exception ex=new Exception();
}
}
class Exception
{
Exception()
{
Scanner s=new Scanner(System.in);
System.out.print("Enter a and b values:");
int a=s.nextInt();
int b=s.nextInt();
try
{
int c=a/b;
System.out.print(c);
}
catch(ArithmeticException ae)
{
System.out.println("Arthmatic Exception occured");
}
}
}
b).Write a JAVA program Illustrating Multiple catch clauses
import java.util.Scanner;
class Multiple_catch
{
public static void main(String args[])
{
Handle h=new Handle();
}
}
class Handle
{
Handle()
{
Scanner sc=new Scanner(System.in);
String str="The world is runs throgh software industry";
String str2=null;
System.out.print("Enter the index of 1st string where you want to retrive the charecter:");
int n1=sc.nextInt();
System.out.print("Enter the index of 2st string where you want to retrive the charecter:");
int n2=sc.nextInt();
try
{
char c=str.charAt(n1);
System.out.println("Charecter at the index of "+n1+" 1st string is:"+c);
char ch=str2.charAt(n2);
System.out.println(ch);
}
catch(StringIndexOutOfBoundsException sib)
{
System.out.println("String index out of range");
}
catch(NullPointerException np)
{
System.out.println("Null pointer exception");
}
}
}
Output :
Enter the index of 1st string where you want to retrive the charecter:-1
Enter the index of 2st string where you want to retrive the charecter:2
String index out of range
Output :
Enter the index of 1st string where you want to retrive the charecter:3
Enter the index of 2st string where you want to retrive the charecter:2
Charecter at the index of 3 1st string is:
Null pointer exception
Exercise – 8 (Runtime Polymorphism)
a). Write a JAVA program that implements Runtime polymorphism
import java.util.Scanner;
class One
{
int a,b;
void sum()
{
Scanner s=new Scanner(System.in);
System.out.print("Enter a and b values:");
a=s.nextInt();
b=s.nextInt();
int sum=a+b;
System.out.println("Sum of two numbers in the class 'One' is:"+sum);
}
}
class Two extends One
{
int a=90,b=67;
int add;
void sum()
{
add=a+b;
System.out.println("Sum of the numbers in the class 'Two' is:"+add);
}
}
class Poly
{
public static void main(String args[])
{
One obj=new One();
obj.sum();
One t=new Two();
t.sum();
}
}
b). Write a Case study on run time polymorphism, inheritance that implements in above problem
Polymorphism:-
Polymorphism is the process of performing the single task in different ways. Polymorphism is the Greek word . In which ‘poly‘ means many and ‘morphs ’ means forms. It means many forms .
Polymorphism is classified into two types they are-
1. Static or Compile time Polymorphism
2. Dynamic or Run time Polymorphism
Runtime Polymorphism:-
Runtime Polymorphism is also called as Dynamic polymorphism. It is the process of calling the Overriding methods in runtime rather than In compile time.
In this process the overriding methods are called with reference of super class.
Explanation:-
In the above program we use single inheritance two achieve the runtime polymorphism in our example.
We use two classes here. We call the base class with the reference of the super class.
We create different objects to the two classes and call the both base class as well as super class with reference of super class only.
So, Runtime polymorphism is achieved here.
Exercise – 9 (User Defined Exception)
a). Write a JAVA program for creation of illustrating throw
public class TestThrow1
{
void validate()
{
try
{
System.out.println("Inside of the try block");
throw new ArithmeticException("Not valid,throwing Exception");
}
catch(ArithmeticException ae)
{
System.out.println(ae);
}
}
public static void main(String args[])
{
TestThrow1 t=new TestThrow1();
t.validate();
}
}
b). Write a JAVA program for creation of Illustrating finally
class TestFinallyBlock
{
public static void main(String args[])
{
try
{
int data=25/5;
System.out.println(data);
}
catch(NullPointerException e)
{
System.out.println(e);
}
finally
{
System.out.println("finally block is defaultly executed");
}
System.out.println("rest of the code...");
}
c). Write a JAVA program for creation of Java Built-in Exceptions
import java.util.Scanner;
class Demo
{
public static void main(String args[])
{
ArrayIndex_Demo obj=new ArrayIndex_Demo();
obj.display();
}
}
class ArrayIndex_Demo
{
void display()
{
Scanner sc=new Scanner(System.in);
System.out.print("Enter the element you want to insert:");
int n=sc.nextInt();
System.out.print("Enter the index of the array:");
try
{
int a[] = new int[5];
int i=sc.nextInt();
a[i]=n;
}
catch (ArrayIndexOutOfBoundsException e)
{
System.out.println("Array Index is Out Of Bounds");
}
}
}
d).Write a JAVA program for creation of User Defined Exception
import java.lang.Exception;
class Myexception extends Exception
{
private static double bal[]={10000.00,12000.00,5600.50,999.00,1100.55};
Myexception(String str)
{
super(str);
}
public static void main(String args[])
{
try
{
for(int i=0;i<=5;i++)
{
System.out.println(bal[i]);
if(bal[i]<1000)
{
Myexception me=new Myexception("This is user defined Error.");
throw me;
}
}
}
catch(Myexception me)
{
me.printStackTrace();
}
}
}
Exercise – 10 (Threads)
a). Write a JAVA program that creates threads by extending Thread class . First thread display
"Good Morning " every 1 sec, the second thread displays "Hello"every 2 seconds and the
third display Welcome" every 3 seconds , (Repeat the same by implementing Runnable)
import java.io.*;
class A extends Thread
{
synchronized public void run()
{
try
{
while(true)
{
sleep(1000);
System.out.println("good morning");
}
}
catch(Exception e)
{ }
}
}
class B extends Thread
{
synchronized public void run()
{
try
{
while(true)
{
sleep(2000);
System.out.println("hello");
}
}
catch(Exception e)
{ }
}
}
class C extends Thread
{
synchronized public void run()
{
try
{
while(true)
{
sleep(3000);
System.out.println("welcome");
}
}
catch(Exception e)
{ }
}
}
class Threadmsgs
{
public static void main(String args[])
{
A t1=new A();
B t2=new B();
C t3=new C();
t1.start();
t2.start();
t3.start();
}
}
b). Write a program illustrating isAlive and join ()
public class AliveJoin extends Thread
{
public void run()
{
System.out.println("ABDUL KALAM ");
try
{
Thread.sleep(300);
}
catch (InterruptedException ie)
{ }
System.out.println("SUBHASH CHANDRABOSH ");
}
public static void main(String[] args)
{
AliveJoin c1 = new AliveJoin();
AliveJoin c2 = new AliveJoin();
c1.start();
c2.start();
System.out.println(c1.isAlive());
System.out.println(c2.isAlive());
try
{
c1.join(); // Waiting for c1 to finish
}
catch (InterruptedException ie)
{ }
}
}
c). Write a Program illustrating Daemon Threads.
import java.io.*;
public class DaemonThread extends Thread
{
public DaemonThread(String name)
{
super(name);
}
public void run()
{
if(Thread.currentThread().isDaemon())
{
System.out.println(getName() + " is Daemon thread");
}
else
{
System.out.println(getName() + " is User thread");
}
}
public static void main(String[] args)
{
DaemonThread t1 = new DaemonThread("t1");
DaemonThread t2 = new DaemonThread("t2");
DaemonThread t3 = new DaemonThread("t3");
t1.setDaemon(true);
t1.start();
t2.start();
t3.setDaemon(true);
t3.start();
}
}
Exercise – 11 (Producer & consumer problem)
Java program that implements producer consumer problem. It is an example for multi process synchronization, where producer always produces and consumer always consumes.The consumer consumes only after the producer produces.
class Thread1{ int num; boolean vs=false; synchronized int get() { if (!vs) try { wait(); } catch (Exception e) { System.out.println("Excepton occurs at : "+e); } System.out.println("get" +num); try { Thread.sleep(1000); } catch (Exception e) { System.out.println("Excepton occurs at : "+e); } vs=false; notify(); return num; } synchronized int put(int num) { if (vs) try { wait(); } catch (Exception e) { System.out.println("Excepton occur at : "+e); } this.num=num; vs=true; System.out.println("put"+num); try { Thread.sleep(1000); } catch (Exception e) { System.out.println("Excepton occur at : "+e); } notify(); return num; }}class Producer implements Runnable{ Thread1 t; Producer(Thread1 t) { this.t=t; new Thread(this,"Producer").start(); } public void run() { int x=0; int i = 0; while (x<10) { t.put(i++); x++; } }}class Consumer implements Runnable{ Thread1 t; Consumer(Thread1 t) { this.t=t; new Thread(this,"Consumer").start(); } public void run() { int x=0; while (x<10) { t.get(); x++; } }}class ProducerConsumer{ public static void main(String[] args) { Thread1 t=new Thread1(); new Producer(t); new Consumer(t); }
Aim: To write a case study on thread Synchronization after solving the above producer consumer problem
A case study on thread synchronization after solving producer consumer problem:
v
We can use wait, notify and notifyAll methods to communicate between
threads inJava.
v For example, if we have two threads running in your
program e.g.Producer and Consumer then producer thread can communicate to the consumer that it can start consuming now
because there are items to consume in thequeue.
v Similarly, a consumer thread
can tell the producer that it can also start putting items now because there is
some space in the queue, which is created as a result ofconsumption.
v
A thread can use wait() method to pause and do nothing depending upon
somecondition.
v For
example, in the producer-consumer problem, producer
thread should wait if the queue is full and consumer thread should wait if the
queue isempty.
v If some
thread is waiting for some condition to become true, we can use notify and notifyAll methods to inform them that
condition is now changed and they can wakeup.
v Both notify() and
notifyAll() method sends a notification but notify sends the notification to
only one of the waiting thread, no guarantee which thread will receive
notification and notifyAll() sends the notification to allthreads.
Things to remember:
1. We can use wait() and notify() method to implement inter-thread
communicationin Java. Not just one or two threads but multiple threads can
communicate to each other by using thesemethods.
2. Always call
wait(), notify() and notifyAll() methods from synchronized method or
synchronizedblock otherwise JVM will throwIllegalMonitorStateException.
3. Always call wait and notify
method from a loop and never from if() block, because loop test waiting
condition before and after sleeping and handles notification even if waiting
for the condition is not changed.
4. Always call wait in shared
object e.g. shared queue in thisexample.
5. Prefer notifyAll() over
notify() method due to reasons given in thisarticle
Exercise – 12 (Packages)
a). Write a JAVA program illustrate class path
import java.net.URL;
import java.net.URLClassLoader;
public class App{
public static void main(String[] args)
{
ClassLoader sysClassLoader = ClassLoader.getSystemClassLoader();
URL[] urls = ((URLClassLoader)sysClassLoader).getURLs();
for(int i=0; i< urls.length; i++)
{
System.out.println(urls[i].getFile());
}
}
}
b). Write a case study on including in class path in your OS environment of your package.
COPEING THE PATH OF JAVA:-
First of all go to MYCOMPUTER and go to the drive where the java is installed.In that go to
PROGRAM FILES and then double click on java folder.
In that we have observed there is a folder with name java jdk,double click on the java jdk folder
and then go into the bin folder.
At this time we have to copy the path of the bin folder.
SETTING THE JAVA PATH:-
Inorder to set the path of the java in our system,first of all we need to open CONTROL PANEL
in our system and go to SYSTEM SETTINGS .
In system settings we need to go into the ADVANCED SYSTEM SETTINGS settings.
In advanced system settings we just click on ENVIRONMENT VARIABLES option.
In USER VARIABLES click on NEW button and type the " path" at VARIABLE NAME.
We need to paste the previously copied path of the bin folder at the place of VARIABLE VALUE.
Finally click on OK and then OK,then close the MYCOMPUTR window.Now the java path is set.We are ready to use java facilities in our computer.
c). Write a JAVA program that import and use the defined your package in the previous Problem
1)
package pack;
public class Addition
{
private double d1,d2;
public Addition(double a, double b)
{
d1=a;
d2=b;
}
public void sum()
{
System.out.println("Sum inside of class Addition is:"+(d1+d2));
}
}
Compilation of the program :- javac -d . Addition.java
2).
import pack.Addition;
class Use
{
public static void main(String args[])
{
Addition obj=new Addition(10,15.5);
obj.sum();
}
}
Exercise - 13 (Applet)
a).Write a JAVA program to paint like paint brush in applet.
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class MouseDrag extends Applet implements MouseMotionListener
{
public void init()
{
addMouseMotionListener(this);
setBackground(Color.red);
}
public void mouseDragged(MouseEvent me)
{
Graphics g=getGraphics();
g.setColor(Color.white);
g.fillOval(me.getX(),me.getY(),10,10); // (x-position, y-postion, width, height)
}
public void mouseMoved(MouseEvent me)
{
}
}
Applet Code: Applet Code save as .html file.
<html>
<applet code="MouseDrag.class" height=300 width=400>
</applet>
</html>
b) Write a JAVA program to display analog clock using Applet.
import java.applet.*;
import java.awt.*;
import java.util.*;
import java.text.*;
public class MyClock extends Applet implements Runnable
{
int width, height;
Thread t = null;
boolean threadSuspended;
int hours=0, minutes=0, seconds=0;
String timeString = "";
public void init()
{
width = getSize().width;
height = getSize().height;
setBackground( Color.black );
}
public void start()
{
if ( t == null )
{
t = new Thread( this );
t.setPriority( Thread.MIN_PRIORITY );
threadSuspended = false;
t.start();
}
else
{
if ( threadSuspended )
{
threadSuspended = false;
synchronized( this )
{
notify();
}
}
}
}
public void stop()
{
threadSuspended = true;
}
public void run()
{
try
{
while (true)
{
Calendar cal = Calendar.getInstance();
hours = cal.get( Calendar.HOUR_OF_DAY );
if ( hours> 12 ) hours -= 12;
minutes = cal.get( Calendar.MINUTE );
seconds = cal.get( Calendar.SECOND );
SimpleDateFormat formatter = new SimpleDateFormat( "hh:mm:ss", Locale.getDefault() );
Date date = cal.getTime();
timeString = formatter.format( date );
// Now the thread checks to see if it should suspend itself
if ( threadSuspended )
{
synchronized( this )
{
while ( threadSuspended )
{
wait();
}
}
}
repaint();
t.sleep( 1000 ); // interval specified in milliseconds
}
}
catch (Exception e)
{
}
}
void drawHand( double angle, int radius, Graphics g )
{
angle -= 0.5 * Math.PI;
int x = (int)( radius*Math.cos(angle) );
int y = (int)( radius*Math.sin(angle) );
g.drawLine( width/2, height/2, width/2 + x, height/2 + y );
}
void drawWedge( double angle, int radius, Graphics g )
{
angle -= 0.5 * Math.PI;
int x = (int)( radius*Math.cos(angle) );
int y = (int)( radius*Math.sin(angle) );
angle += 2*Math.PI/3;
int x2 = (int)( 5*Math.cos(angle) );
int y2 = (int)( 5*Math.sin(angle) );
angle += 2*Math.PI/3;
int x3 = (int)( 5*Math.cos(angle) );
int y3 = (int)( 5*Math.sin(angle) );
g.drawLine( width/2+x2, height/2+y2, width/2 + x, height/2 + y );
g.drawLine( width/2+x3, height/2+y3, width/2 + x, height/2 + y );
g.drawLine( width/2+x2, height/2+y2, width/2 + x3, height/2 + y3 );
}
public void paint( Graphics g )
{
g.setColor( Color.white );
drawWedge( 2*Math.PI * hours / 12, width/5, g );
drawWedge( 2*Math.PI * minutes / 60, width/3, g );
drawHand( 2*Math.PI * seconds / 60, width/2, g );
g.setColor( Color.white );
g.drawString( timeString, 10, height-10 );
}
}
Applet Code: Applet Code save as .html file.
<html>
<applet code="MyClock.class" height=300 width=400>
</applet>
</html>
c). Write a JAVA program to create different shapes and fill colors using Applet.
import java.applet.*;
import java.awt.*;
public class ShapeColor extends Applet
{
int x=300,y=100,r=50;
public void paint(Graphics g)
{
g.setColor(Color.red); //Drawing line color is red
g.drawLine(3,300,200,10);
g.setColor(Color.magenta);
g.drawString("Line",100,100);
g.drawOval(x-r,y-r,100,100);
g.setColor(Color.yellow); //Fill the yellow color in circle
g.fillOval( x-r,y-r, 100, 100 );
g.setColor(Color.magenta);
g.drawString("Circle",275,100);
g.drawRect(400,50,200,100);
g.setColor(Color.yellow); //Fill the yellow color in rectangel
g.fillRect( 400, 50, 200, 100 );
g.setColor(Color.magenta);
g.drawString("Rectangel",450,100);
}
}
Applet Code: Applet Code save as .html file.
<html>
<applet code="ShapeColor.class" height=300 width=400>
</applet>
</html>
Exercise - 14 (Event Handling)
a).Write a JAVA program that display the x and y position of the cursor movement using
Mouse.
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
public class AppletMouse extends Applet implements MouseListener, MouseMotionListener
{
int x, y;
String str="";
public void init()
{
addMouseListener(this);
addMouseMotionListener(this);
}
// override ML 5 abstract methods
public void mousePressed(MouseEvent e)
{
x = e.getX();
y = e.getY();
str = "Mouse Pressed";
repaint();
}
public void mouseReleased(MouseEvent e)
{
x = e.getX();
y = e.getY();
str = "Mouse Released";
repaint();
}
public void mouseClicked(MouseEvent e)
{
x = e.getX();
y = e.getY();
str = "Mouse Clicked";
repaint();
}
public void mouseEntered(MouseEvent e)
{
x = e.getX();
y = e.getY();
str = "Mouse Entered";
repaint();
}
public void mouseExited(MouseEvent e)
{
x = e.getX();
y = e.getY();
str = "Mouse Exited";
repaint();
}
// override two abstract methods of MouseMotionListener
public void mouseMoved(MouseEvent e)
{
x = e.getX();
y = e.getY();
str = "Mouse Moved";
repaint();
}
public void mouseDragged(MouseEvent e)
{
x = e.getX();
y = e.getY();
str = "Mouse dragged";
repaint();
}
// called by repaint() method
public void paint(Graphics g)
{
g.setFont(new Font("Monospaced", Font.BOLD, 20));
g.fillOval(x, y, 10, 10);
g.drawString(x + "," + y, x+10, y -10);
g.drawString(str, x+10, y+20);
showStatus(str + " at " + x + "," + y);
}
}
Applet code:Applet code save as .html file
<html>
<body>
<applet code="AppletMouse.class" width="300" height="300">
</applet>
</body>
</html>
b).Write a JAVA program that identifies key-up key-down event user entering text in a Applet.
import java.applet.Applet;
import java.awt.*;
public class KeyUpDown1 extends Applet {
private Font f;
private String letter;
private boolean first;
public void init()
{
f = new Font( "Courier", Font.BOLD, 72 );
first = true;
}
public void paint( Graphics g )
{
g.setFont( f );
if ( !first )
g.drawString( letter, 75, 70 );
}
public boolean keyDown( Event e, int key )
{
showStatus( "keyDown: the " + ( char ) key +
" was pressed." );
letter = String.valueOf( ( char ) key );
first = false;
repaint();
return true; // event has been handled
}
public boolean keyUp( Event e, int key )
{
showStatus( "keyUp: the " + ( char ) key +
" was released." );
return true; // event has been handled
}
}
Applet code:Applet code save as .html
<html>
<body>
<applet code="KeyUpDown1.class" width="300" height="300">
</applet>
</body>
</html>
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