Use of HashMap

import java.util.*;
class BookId implements Comparator{
public int compare(Object o1,Object o2){
return ((Book)o1).book_id-((Book)o2).book_id;
}
}
class BookName implements Comparator{
public int compare(Object o1,Object o2){
return ((Book)o1).title.compareTo(((Book)o2).title);
}
}
public class Book implements Comparable{
/**
Unique Book ID
                */
public int book_id;
protected String title;
/**
Book Price including GST
                */
private float price;
/**
Constructor
                */
public Book(int id, String title, float price){
this.book_id = id;
this.title = title;
this.price = price;
}
public int compareTo(Object o1){
return (int)(this.price-(((Book)o1).price));
}
public String toString(){
return this.book_id+"#"+this.title+"#"+this.price+"@";
}

public static String ObjToString(Book c[]){
String str = new String();
for(int i=0;i<c.length;i++){
str = str+c[i];
}
return str;
}

public static Book[] StringToObj(String str){
String[] st = str.split("@");
Book b2[] = new Book[st.length];

for(int i=0; i<st.length;i++){
String st1[] = st[i].split("#");
b2[i] = new Book(Integer.parseInt(st1[0]),st1

[1],Float.parseFloat(st1[2]));
}
return b2;
}

public static void main(String args[]){

//ArrayList a1 = new ArrayList();
//TreeSet a1 = new TreeSet();
HashMap<Integer,Book> a1 = new HashMap<Integer,Book>();

a1.put(new Integer(1),new Book(2,"ADA", 200));
a1.put(new Integer(3),new Book(1,"Java", 500));
a1.put(new Integer(2),new Book(4,"MI", 800));
//Collections.sort(a1,new BookName());
Collection<Book> a2 = a1.values();
Iterator ir = a2.iterator();

while(ir.hasNext())
{
System.out.println((Book)(ir.next()));
}


/*System.out.print(Book.ObjToString(b));
String str1 = ObjToString(b);

Book c[] = StringToObj(str1);
for(int i=0;i<c.length;i++){
System.out.print(c[i]);
}*/
}
}

Use of Collection Framework

Use of Collection Framework Classes and Interfaces

ArrayList, TreeSet, Iterator

import java.util.*;

public class Book implements Comparable{

/**

Unique Book ID

                */

public int book_id;

protected String title;

/**

Book Price including GST

                */

private float price;

/**

Constructor

                */

public Book(int id, String title, float price){

this.book_id = id;

this.title = title;

this.price = price;

}

public int compareTo(Object o1){

return this.book_id-(((Book)o1).book_id);

}

public String toString(){

return this.book_id+"#"+this.title+"#"+this.price+"@";

}

public static String ObjToString(Book c[]){

String str = new String();

for(int i=0;i<c.length;i++){

str = str+c[i];

}

return str;

}

public static Book[] StringToObj(String str){

String[] st = str.split("@");

Book b2[] = new Book[st.length];

for(int i=0; i<st.length;i++){

String st1[] = st[i].split("#");

b2[i] = new Book(Integer.parseInt(st1[0]),st1[1],Float.parseFloat(st1[2]));

}

return b2;

}

public static void main(String args[]){

Book b[] = new Book[3];

b[0] =new Book(1,"Java", 100);

b[1] = new Book(2,"ADA", 200);

b[2] = new Book(3,"SP", 300);

//ArrayList a1 = new ArrayList();

TreeSet a1 = new TreeSet();

a1.add(new Book(2,"ADA", 200));

a1.add(new Book(2,"ADA", 200));

a1.add(new Book(1,"Java", 500));

a1.add(new Book(4,"MI", 800));

// Collections.sort(a1);

Iterator ir = a1.iterator();

while(ir.hasNext())

{

System.out.println((Book)(ir.next()));

}

System.out.print(a1);

/*System.out.print(Book.ObjToString(b));

String str1 = ObjToString(b);

Book c[] = StringToObj(str1);

for(int i=0;i<c.length;i++){

System.out.print(c[i]);

}*/

}

}

Array of Object to String and String to Array of Object

class Book{
int book_id;
String title;
float price;

Book(int id, String title, float price){
this.book_id = id;
this.title = title;
this.price = price;
}

public String toString(){
return this.book_id+"#"+this.title+"#"+this.price+"@";
}

public static String ObjToString(Book c[]){
String str = new String();
for(int i=0;i<c.length;i++){
str = str+c[i];
}
return str;
}

public static Book[] StringToObj(String str){
String[] st = str.split("@");
Book b2[] = new Book[st.length];

for(int i=0; i<st.length;i++){
String st1[] = st[i].split("#");
b2[i] = new Book(Integer.parseInt(st1[0]),st1[1],Float.parseFloat(st1[2]));
}
return b2;
}

public static void main(String args[]){

Book b[] = new Book[3];

b[0] =new Book(1,"Java", 100);
b[1] = new Book(2,"ADA", 200);
b[2] = new Book(3,"SP", 300);


System.out.print(Book.ObjToString(b));
String str1 = ObjToString(b);

Book c[] = StringToObj(str1);
for(int i=0;i<c.length;i++){
System.out.print(c[i]);
}
}
}

Demo Socket Program

Server Side :
import java.net.*;
import java.io.*;
class Server
{
public static void main(String s[]) throws Exception
{
ServerSocket ss=new ServerSocket(5000);
Socket s1=ss.accept();
System.out.println(s1);
DataOutputStream d1=new DataOutputStream(s1.getOutputStream());
d1.writeUTF("Hello Client");
d1.flush();
d1.close();
}
}


Client Side:
import java.net.*;
import java.io.*;
class Client
{
public static void main(String s[]) throws Exception
{
Socket ss=new Socket("localhost",5000);
DataInputStream d1=new DataInputStream(ss.getInputStream());
System.out.println(d1.readUTF());
d1.close();
}
}

Wrapper Class and Primitive Data Types

Wrapper Class and Primitive Data Types