Java practice programs for beginners
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JAVA PRACTICE PROGRAMS FOR BEGINNERS WITH SOLUTIONS by Ishan Sharma
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Transcript of Java practice programs for beginners
JAVA PRACTICE PROGRAMS FOR
BEGINNERS WITH SOLUTIONS
by Ishan Sharma
public class javaprog1{
String str1,str2,str3;
static int count;
javaprog1(){
count++;
}
javaprog1(String s1){
str1 = s1;
count++;
}
javaprog1(String s2,String s3){
str2 = s2;
str3 = s3;
count++;
}
WAP program to show constructor
overloading using static member
public static void main(String args[]){
javaprog1 obj1 = new javaprog1();
javaprog1 obj2 = new javaprog1("string 1");
javaprog1 obj3 = new javaprog1("string 2","string 3");
System.out.println("number of times static variable used : "+count);
}
}.
WAP to implement multilevel
inheritance and method overriding
class parent{
public void function(){
System.out.println("In parent class");
}
}
class child1 extends parent{
public void function(){
System.out.println("In child1 class");
}
}
class child2 extends parent{
public void function(){
System.out.println("In child2 class");
}
}
public class javaprog2{
public static void main(String args[]){
parent obj = new parent();
obj.function();
child1 obj_c1 = new child1();
child2 obj_c2 = new child2();
obj = obj_c1;
obj.function();
obj = obj_c2;
obj.function();
}
}
WAP to implement interface class
and show use of package
// JavaProg3 is a different
//package
package JavaProg3;
public interface javaprog3{
public void print(String str_arg);
}
import JavaProg3.*;
public class javaprog4 implements javaprog3{
public void print( String str_arg){
System.out.println(str_arg);
}
public static void main(String args[]){
javaprog4 obj = new javaprog4();
obj.print(args[0]);
}
}
WAP to implement multilevel
exception handling and create your
own exception import JavaProg3.*;
public class javaprog4 implements javaprog3{
public void print( String str_arg[]){
try{
for(int i=0;i<10;i++)
System.out.println(str_arg[i]+"\n");
}catch(Exception e){
System.out.println("exception caught and re-thrown");
throw(e);
}
}
public static void main(String args[]){
javaprog4 obj = new javaprog4();
try{
obj.print(args);
} catch(Exception e){
System.out.println(e);
}
}
}
WAP to implement 3 threads such that 1st
sleeps for 200ms, 2nd for 400ms and 3rd for
600ms
class NewThread implements Runnable {
Thread t;int time;
NewThread(String str,int time1) {
time = time1;
t = new Thread(this, str);
System.out.println(t);
t.start();
}
public void run() {
try {
for(int i = 5; i > 0; i--) {
System.out.println(t);
Thread.sleep(time);
}
} catch (InterruptedException e) {
System.out.println("Child interrupted.");
}
System.out.println("Exiting"+t);
}
}
class ThreadDemo {
public static void main(String args[]) {
try {
NewThread t1 = new NewThread("thread1",200);
NewThread t2 = new NewThread("thread2",400);
NewThread t3 = new NewThread("thread3",600);
}catch (Exception e) {
System.out.println(" thread interrupted."+e);
}
}
}
WAP to create applet of moving
banner
import java.awt.*;
import java.applet.*;
public class ParamBannerextends Applet implements Runnable {
String msg=" Hello Java...... ";
Thread t = null;
int state;
boolean stopFlag;
public void start() {
setBackground(Color.blue);
setForeground(Color.green);
Font currentFont = new Font("TimesRoman", Font.PLAIN, 40);
setFont(currentFont);
t = new Thread(this);
stopFlag = false;
t.start();
}
public void run() {
char ch;
for( ; ; ) {
try {
repaint();
Thread.sleep(150);
ch = msg.charAt(0);
msg = msg.substring(1, msg.length());
msg += ch;
if(stopFlag)
break;
} catch(InterruptedExceptione) {}
}
}
public void paint(Graphics g) {
g.drawString(msg, 50, 30);
}
}
WAP to make a simple calculator import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class calculator extends JApplet {
JTextField jtf1,jtf2;
JButton add = new JButton("add");
JButton sub = new JButton("sub");
JButton mul = new JButton("mul");
JButton div = new JButton("div");
public void init() {
try {
SwingUtilities.invokeAndWait(
new Runnable() {
public void run() {
makeGUI();
}
}
);
} catch (Exception exc) {
System.out.println("Can't create because of " + exc);
}
}
private void makeGUI() {
setLayout(new FlowLayout());
jtf1 = new JTextField(5);
add(jtf1);
jtf2 = new JTextField(5);
add(jtf2);
add(add);
add(sub);
add(mul);
add(div);
add.addActionListener(new ActionListener() {
public void actionPerformed(ActionEventae) {
int a = Integer.parseInt(jtf1.getText());
int b = Integer.parseInt(jtf2.getText());
int ans = a+b;
StringBuilder str = new StringBuilder();
str.append(ans);
String str1 = str.toString();
showStatus( str1 );
}
});
sub.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
int a = Integer.parseInt(jtf1.getText());
int b = Integer.parseInt(jtf2.getText());
int ans = a-b;
StringBuilder str = new StringBuilder();
str.append(ans);
String str1 = str.toString();
showStatus( str1 );
}
});
mul.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
int a = Integer.parseInt(jtf1.getText());
int b = Integer.parseInt(jtf2.getText());
int ans = a*b;
StringBuilder str = new StringBuilder();
str.append(ans);
String str1 = str.toString();
showStatus( str1 );
}
});
div.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
int a = Integer.parseInt(jtf1.getText());
int b = Integer.parseInt(jtf2.getText());
if(b == 0)
showStatus( "can't be divided by 0" );
else{
int ans = a/b;
StringBuilder str = new StringBuilder();
str.append(ans);
String str1 = str.toString();
showStatus( str1 );
}}
});
}}
Build a client server chat
application //server class
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.*;
public class server implements Runnable {
ServerSocket serversocket;
BufferedReader br1, br2;
PrintWriter pr1;
Socket socket;
Thread t1, t2,t3;
String in="",out="";
public server() {
try {
t1 = new Thread(this);
t2 = new Thread(this);
t3 = new Thread(this);
serversocket = new ServerSocket(9876);
System.out.println("> Server is waiting for client to connect ");
socket = serversocket.accept();
System.out.println("Client connected with Ip " + socket.getInetAddress().getHostAddress());
t1.start();
t2.start();
} catch (Exception e) {
}
}
public void run() {
try {
if (Thread.currentThread() == t1) {
do {
br1 = new BufferedReader(new InputStreamReader(System.in));
pr1 = new PrintWriter(socket.getOutputStream(), true);
in = br1.readLine();
pr1.println(in);
} while (!in.equals("END"));
} else {
do {
br2 = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = br2.readLine();
System.out.println("> Client says : " + out);
} while (!out.equals("END"));
}
} catch (Exception e) {
}
}
public static void main(String[] args) {
new server();
}
}
//client class
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.*;
public class Client implements Runnable {
BufferedReader br1, br2;
PrintWriter pr1;
Socket socket;
Thread t1, t2,t3;
String in = "", out = "";
public Client() {
try {
t1 = new Thread(this);
t2 = new Thread(this);
socket = new Socket("localhost", 9876);
t1.start();
t2.start();
} catch (Exception e) {
}
}
public void run() {
try {
if (Thread.currentThread() == t2 ) {
do {
br1 = new BufferedReader(new InputStreamReader(System.in));
pr1 = new PrintWriter(socket.getOutputStream(), true);
in = br1.readLine();
pr1.println(in);
} while (!in.equals("END"));
} else {
do {
br2 = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = br2.readLine();
System.out.println("> Server says : " + out);
} while (!out.equals("END"));
}
} catch (Exception e) {
}
}
public static void main(String[] args) {
new Client();
}
}
References:
Herbert Schildt
Stackoverflow.com
END OF PRESENTATION
