what is Jshell in Java9

To learn Java in fun way JShell concept are introduce in Java 9

e.g.

First start jshell by just type command jshell PRINTING from  dir.

Java 9 Features

Release September  21, 2017

1-Jshell
2-JPMS(Java Platform module system)
3-JLink(Java Linker)
4-Process API updates
5-private methods inside interface

6-Try With Resource enhancement
7-Factory Methods to create unmodifiable Collection
8-Stream API Enhancement
9-Diamond (< >) Operator Enhancement
10-Http2 Client .
11-Safe Varargs Annotation
12-G1 Garbage Collector being default Garbage Collection.

how to implement stack using dynamic array

public class StackWithArray {

private int capacity = 2;
private int stack[] = new int[capacity];
private int top = 0;

public void push(int data) {

if (size() == capacity)
expand();

stack[top] = data;
top++;

}

private void expand() {
int length = size();

int[] newStack = new int[capacity * 2];
System.arraycopy(stack, 0, newStack, 0, length);
stack = newStack;
capacity *= 2;

}

private int size() {
return top;
}

public int pop() {
int data = 0;
if (isEmpty()) {
System.out.println("stack is empty");
} else {
top--;
data = stack[top];
stack[top] = 0;
shrink();

}
return data;
}

public int peek() {
int data;
data = stack[top - 1];
return data;

}

private void shrink() {
int length = size();
if (length <= (capacity / 2) / 2)
capacity = capacity / 2;

int newStack[] = new int[capacity];
System.arraycopy(stack, 0, newStack, 0, length);
stack = newStack;
}

public boolean isEmpty() {
return top <= 0;
}

public void displayData() {
for (int n : stack) {
System.out.print(n + " ");
}
System.out.println();

}

public static void main(String[] args) {

StackWithArray st = new StackWithArray();
st.push(1);
st.push(2);
st.push(3);
st.push(4);
st.push(5);
st.pop();
st.displayData();
st.pop();
st.displayData();
st.pop();
st.displayData();
st.pop();
st.displayData();

}

}

How To implement Stack in Java

public class MyStack {

int data[]=new int[5];

int top=0;
static int size=0;

public void push(int value) {
data [top]=value;
top++;
size++;
}

int pop() {
int d=0;
for(int i=size-1; i>=0; i--) {
System.out.println(data[i]);
d=data[i];
data[i]=0;
}

return d;
}

public static void main(String[] args) {

MyStack st=new MyStack();
st.push(1);
st.push(5);
st.push(2);
st.push(0);
st.push(1);
st.pop();
}

}

How to implement custom Queue in Java

public class MyQueue {
public static void main(String[] args) {


Queue q = new Queue();
q.enQueue(5);
q.enQueue(8);
q.enQueue(1);
q.enQueue(2);
q.enQueue(3);
q.show();
}
}

class Queue {
int size;
int[] queue;

int front;
int rear;

Queue() {
size = 0;
queue = new int[5];
}

public void enQueue(int data) {
queue[rear] = data;
rear = rear + 1;
size = size + 1;
}

public void show() {
for (int i = 0; i < queue.length; i++) {
System.out.println(queue[i]);
}
}

}

how to create doubly circular linked list in java

package hello;

public class MyLinkedList<E> {

private Node<E> first;
private Node<E> last;
int size;

public MyLinkedList() {
size = 0;
}

public int size() {
return size;
}

public static class Node<E> {
Node<E> next;
Node<E> pre;
E elelement;

public Node(Node p, E e, Node n) {
this.elelement = e;
this.next = n;
this.pre = p;
}

public E getElelement() {
return elelement;
}

public void setElelement(E elelement) {
this.elelement = elelement;
}

public Node<E> getNext() {
return next;
}

public void setNext(Node<E> next) {
this.next = next;
}

public Node<E> getPre() {
return pre;
}

public void setPre(Node<E> pre) {
this.pre = pre;
}

}

public void printForward() {
Node n = first;
for (int i = 0; i < size; i++) {
if (n.getPre() == null) {
System.out.print(n.getPre() + "::" + n.getElelement());
n = n.next;
} else if (n.getNext() == null) {
System.out.println("-->" + n.getElelement() + "::" + n.getNext());
} else {
System.out.print("-->" + n.getElelement() + "::");
n = n.next;
}

}

}

public void printBackward() {

System.out.println();
Node n = last;
for (int i = 0; i < size; i++) {
if (n.getNext() == null) {
System.out.print(n.getNext() + "-->::" + n.getElelement());
n = n.pre;
} else if (n.getPre() == null) {
System.out.println("-->" + n.getElelement() + "::-->" + n.getPre());
} else {
System.out.print("-->" + n.getElelement() + "::");
n = n.pre;
}

}

}

public void add(E e) {
final Node<E> l = last;
final Node<E> newNode = new Node<>(l, e, null);
last = newNode;
if (l == null) {
first = newNode;
} else {
l.next = newNode;
}
size++;
}

public void addCircular(E e) {
final Node<E> l = last;
final Node<E> newNode = new Node<>(l, e, null);
last = newNode;
if (l == null) {
first = newNode;
} else {
l.next = newNode;
newNode.next = first.pre;
first.pre = l.next;
}
size++;
}

public static void main(String[] args) {
MyLinkedList<Integer> iList = new MyLinkedList<Integer>();
iList.add(1);
iList.add(2);
iList.add(3);
iList.add(4);
iList.printForward();
iList.printBackward();
System.out.println("--------------------------------------------------------------");

iList.addCircular(1);
iList.addCircular(2);
iList.addCircular(3);
iList.addCircular(4);
iList.printForward();
// System.out.println(iList.size);
}

}

JPA2 Without Toplink Implemation

Create Model Class


package myPack;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity

public class Emp
{
@Id
int id;
String name,job;
int salary;

public Emp() {
super();
}


public Emp(int id, String name, String job, int salary) {
super();
this.id = id;
this.name = name;
this.job = job;
this.salary = salary;
}


public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}

}

Create Factory Class

package myPack;

import javax.persistence.EntityManager;

import javax.persistence.EntityManagerFactory;

import javax.persistence.Persistence;

public class MyFactory 

{

static EntityManagerFactory EMF;

static 

{

EMF=Persistence.createEntityManagerFactory("JPA1withTopLinkPU");

}

public static EntityManager getManager()

{

return EMF.createEntityManager();

}

}

Create Persist Class

package myPack;

import javax.persistence.EntityManager;

import javax.persistence.*;

public class PersistDemo {

public static void main(String[] args)

{

EntityManager m=MyFactory.getManager();

Emp e1=new Emp(8,"Bharat","Developer",15000);

Emp e2=new Emp(9,"Ankit","Developer",17000);

System.out.println("Persisting Entities...........");

EntityTransaction t=m.getTransaction();

t.begin();

m.persist(e1);

m.persist(e2);

t.commit();

m.close();

System.out.println("SUCCESSFULLY PERISTED");

}

}

Create Persistence Configuration Xml File

<?xml version="1.0" encoding="UTF-8"?>

<persistence xmlns="http://java.sun.com/xml/ns/persistence"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence

    http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">

    

<persistence-unit name="JPA1withTopLinkPU" transaction-type="RESOURCE_LOCAL">

<provider>oracle.toplink.essentials.PersistenceProvider</provider>

  <class>myPack.Emp</class>

  <properties>

<property name = "toplink.jdbc.driver" value = "oracle.jdbc.driver.OracleDriver"/>

<property name = "toplink.jdbc.url" value = "jdbc:oracle:thin:@localhost:1521:xe"/>

<property name = "toplink.jdbc.user" value = "system"/>

<property name = "toplink.jdbc.password" value = "oracle"/>

  </properties>

</persistence-unit>

  

</persistence>

Create FetchTest Class

package myPack;

import java.util.Scanner;

import javax.persistence.EntityManager;

public class FetchTest {

public static void main(String[] args) {

EntityManager m=MyFactory.getManager();

Scanner in=new Scanner(System.in);

System.out.println("Enter your id:");

int id=in.nextInt();in.nextLine();

System.out.println("Find method used........");

Emp e1=m.find(Emp.class, id);

System.out.println("Details of fetchd entity using data memeber:");

System.out.println(e1.name+"\t"+e1.job+"\t"+e1.salary);

System.out.println("Details of fetched entity getter Methods");

System.out.println(e1.getName()+"\t"+e1.getJob()+"\t"+e1.getSalary());

System.out.println("GetReference method used......");

Emp e=m.getReference(Emp.class,id);

System.out.println("Details of fetchd entity using data memeber:");

System.out.println(e.name+"\t"+e.job+"\t"+e.salary);

System.out.println("Details of fetched entity getter Methods");

System.out.println(e.getName()+"\t"+e.getJob()+"\t"+e.getSalary());

m.close();

}

}

Struts2 Hibernate Integration java programmer can use it in simplified manner

 Create A Model Class  A class:

package Model;

public class Emp
{

String name,job;
int salary;
int id;
public Emp() {
super();
// TODO Auto-generated constructor stub
}
public Emp(String name, String job, int salary) {
super();
this.name = name;
this.job = job;
this.salary = salary;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}

}

Create Hibernate Session Factory

package HibernateUtile;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class MySesssionFactory
{
static SessionFactory factory;
static
{
Configuration cfg=new Configuration().configure();
factory=cfg.buildSessionFactory();
}
public static Session getSession()
{
return factory.openSession();
}
}

Create Dao Class

package Dao;

import org.hibernate.Session;

import org.hibernate.Transaction;

import HibernateUtile.MySesssionFactory;

import Model.Emp;

public class EmpDao

{

public void insert(Emp emp)

{

Session session=MySesssionFactory.getSession();

Transaction tr=session.beginTransaction();

session.save(emp);

tr.commit();

session.close();

}

}

Create Hibernate Configuration

 <?xml version='1.0' encoding='UTF-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<!-- Generated by MyEclipse Hibernate Tools.                   -->

<hibernate-configuration>

    <session-factory>

        <property name="connection.username">system</property>

        <property name="connection.url">jdbc:oracle:thin:@localhost:1521:xe</property>

        <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>

        <property name="connection.password">oracle</property>

        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

    <property name="show_sql">true</property>

    <mapping resource="Hibernate.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

Create Hibernate Mapping File

<?xml version='1.0' encoding='UTF-8'?>

<!DOCTYPE hibernate-mapping PUBLIC

          "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

          "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!-- Generated by MyEclipse Hibernate Tools.                   -->

<hibernate-mapping>

 <class name="Model.Emp">

    <id name="id" type="int">

    <generator class="increment"/>

    </id>

    <property name="name"/>

    <property name="job"/>

    <property name="salary" type="int"/>

</class>

</hibernate-mapping>

Create Controller Page

package View;

import Dao.EMpDao;

import Model.Emp;

public class ActionAaAview

{

private Emp e;

public Emp getE() {

return e;

}

public void setE(Emp e) {

this.e = e;

}

public String execute()

{

EmpDao ctr=new EmpDao();

ctr.insert(e);

return "success";

}

}

Create struts.xml file

<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
<package name="demo" extends="struts-default">
<action name="add" class="View.ActionAaAview">
<result name="success">/Welcome.jsp</result>
<!--<result name="failure">/Retrive.jsp</result>-->
</action>
</package>
</struts>



Copy bellow text and paste in web.xml file


<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.5" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <filter>
  <filter-name>f1</filter-name>
  <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
  </filter>
  <filter-mapping>
  <filter-name>f1</filter-name>
  <url-pattern>/*</url-pattern>
  </filter-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>


Create index.jsp

<%@taglib prefix="s" uri="/struts-tags"%>

<s:form action="add" >

<s:textfield name="Emp.name" label="Name"/>
<s:textfield name="Emp.job" label="Job"/>
<s:textfield name="Emp.salary" label="Salary"/>
<s:token/>
<s:submit name="Register"/>
<s:reset name="Reset"/>


</s:form>



Create welcome.jsp

<%@taglib prefix="s" uri="/struts-tags"%>
Welcome<s:property value="Emp.name"/>

</s:form>


Create retrive.jsp

<%@taglib prefix="s" uri="/struts-tags"%>
<s:form action="add" method="post">
<s:textfield name="name" label="Name"/>
<s:textfield name="job" label="Job"/>
<s:textfield name="salary" label="Salary"/>
<s:submit name="Register"/>
<s:reset name="Reset"/>
<s:textfield />

</s:form>