Node code in java

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Using node.js from Java, NetBeans and JShell

jtulach/node4j

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README.md

Here is few things that you need:

• Download Graal VM from OTN (current sources were tested with GraalVM 0.19 — 0.23)
• Install Maven
• Get the sources: git clone https://github.com/jtulach/node4j

With these components, it should be easy to execute your first node.js application from Java:

$ cd node4j $ JAVA_HOME=/path/to/graalvm/ mvn package exec:exec Server listening on port 8080

Now you can connect to the http://localhost:8080/someurl and verify the application works. It should. But the best thing is that the application isn’t written in JavaScript, but in Java:

package org.netbeans.demo.node4j; import net.java.html.lib.Function; import net.java.html.lib.node.http.Exports; import net.java.html.lib.node.http.IncomingMessage; import net.java.html.lib.node.http.ServerResponse; import net.java.html.lib.node.http.Server; public final class Main < public static void main(String. args) < Server server = Exports.createServer((IncomingMessage request, ServerResponse response) -> < System.err.println("request for " + request.url()); response.end("It works! Hit " + request.url()); return null; >); server.listen(8080, Function.newFunction((Function.A0Void>) () -> < System.err.println("Server listening on port 8080"); return null; >)); > >

All the power of node.js engine accessible from regular Java virtual machine via type-safe Java APIs!

Using NetBeans and JShell

The whole node4j project is a typical Maven project and you can work with it from any IDE that speaks Maven. However, if you download NetBeans IDE with built in support for JShell, we can do even more!

• Start the NetBeans 9 IDE (preview builds available): netbeans —jdkhome /path/to/jdk9
• Open the node4j project
• Configure it to use GraalVM 0.23 or newer in File/Properties
• Execute the project

A JShell console opens up in the editor and you can easily start using all the node.js features interactively from Java. Type:

and press Ctrl-Space to invoke code completion. From the list of available choices select createServer method with one requestListener parameter. Following will be generated:

[19] -> createServer(requestListener)

press Ctrl-Space once again and let the IDE generate the lamda function body:

[19] -> createServer((p1, p2) -> < return null; >)

optionally rename p1 to in and p2 to out as that is the meaning of the callback parameters in this context. Type in a lamda body to generate a reply:

[19] -> createServer((p1, p2) -> < p2.end("Hello from Java!\n"); return null; >)

after placing the caret at the end of the code snippet and pressing Enter, the snippet is evaluated:

| Expression value is: [object Object] | assigned to temporary variable $53 of type Server

and the value is stored in variable $53 . Try to use that variable, type:

and press Ctrl-Space to see methods available on this object. Choose listen method with one number parameter and bind the server to that port:

[20] -> $53.listen(2345) | Expression value is: | assigned to temporary variable $64 of type Server

Your first interactive JShell+Node.js session is done. Connect to http://localhost:2345 to verify the server works.

About

Using node.js from Java, NetBeans and JShell

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Java Node Example

An Individual Node in java is a class that is used to create the individual data holding blocks for various data structures, which organize data in a nonsequential fashion.

2. Implementations of Node class

A Node class can be customized to store one or more data fields and pointer links inside each of the individual objects, depending on the needs of the required data structure.

2.1 Node class in Linked List

1. Data Field, which contains the data stored in the current Node.
2. Pointer Field of type Node, which contains the address information of the next Node in the Linked List.

The following code snippet will show the structure of the Node Class in the Singly Linked List.

public class SinglyLinkedListNode < protected int data; protected SinglyLinkedListNode next; public SinglyLinkedListNode() < next = null; data = 0; >public SinglyLinkedListNode(int d, SinglyLinkedListNode n) < data = d; next = n; >public void setLinkNext(SinglyLinkedListNode n) < next = n; >public SinglyLinkedListNode getLinkNext() < return next; >public void setData(int d) < data = d; >public int getData() < return data; >>

In the above code snippet, the next is the pointer to the next node in the Singly Linked List and data is the value stored in the current node of Singly Linked List.

2.2 Node class in Doubly Linked List and Binary Tree

In this section we will discuss the node class used in defining a Doubly Linked List and Binary tree.

In case of Both DLL and Binary Tree, the Node class contains 3 values.

1. Data Field, which contains the data stored in the current Node.
2. Next Pointer Field of type Node, which contains the address information of the next Node in the Linked List.
3. Prev Pointer Field of type Node, which contains the address information of the previous Node in the Linked List.

Following Code snippet will show the structure of the Node Class in Doubly Linked List. DoublyLinkedListNode.java

public class DoublyLinkedListNode < protected int data; protected DoublyLinkedListNode next, prev; public DoublyLinkedListNode() < next = null; prev = null; data = 0; >public DoublyLinkedListNode(int d, DoublyLinkedListNode n, DoublyLinkedListNode p) < data = d; next = n; prev = p; >public void setLinkNext(DoublyLinkedListNode n) < next = n; >public void setLinkPrev(DoublyLinkedListNode p) < prev = p; >public DoublyLinkedListNode getLinkNext() < return next; >public DoublyLinkedListNode getLinkPrev() < return prev; >public void setData(int d) < data = d; >public int getData() < return data; >>

In the above code snippet, the next is the pointer to the next node and prev is the pointer to the previous node in the Doubly Linked List and data is the value stored in the current node of Doubly Linked List.

1. Data Field, which contains the data stored in the current Node.
2. Left Pointer Field of type Node, which contains the address information of the root Node of Left Subtree in Binary Tree or null for leaf pointer.
3. Right Pointer Field of type Node, which contains the address information of the root Node of Right Subtree in Binary Tree or null for leaf pointer.

The following Code snippet will show the structure of the Node Class in Binary Tree. BinaryTreeNode.java

class BinaryTreeNode < int value; BinaryTreeNode left; public int getValue() < return value; >public void setValue(int value) < this.value = value; >public BinaryTreeNode getLeft() < return left; >public void setLeft(BinaryTreeNode left) < this.left = left; >public BinaryTreeNode getRight() < return right; >public void setRight(BinaryTreeNode right) < this.right = right; >BinaryTreeNode right; BinaryTreeNode(int value) < this.value = value; right = null; left = null; >>

In the above code snippet, the right is the pointer to the root of the right subtree node and left is the pointer to the root of the left subtree of the Binary Tree and value is the value stored in the current node of the Binary Tree.

2.3 Node class in N-Ary Tree and Trie

In this section, we will discuss the node class used in defining an N-ary tree and Trie.

1. Data Field, which contains the data stored in the current Node.
2. Pointer Field, which is an array of items of type Node, where each item contains the address information of the next Node in the Linked List.

The following Code snippet will show the structure of the Node Class in N-ary Tree and Trie Linked List. NaryTreeNode.java

import java.util.ArrayList; import java.util.List; public class NaryTreeNode < public NaryTreeNode parentNode; // The parent of the current node public ListchildList; // The children's of the current node public String dataValue; public NaryTreeNode getParentNode() < return parentNode; >public void setParentNode(NaryTreeNode parentNode) < this.parentNode = parentNode; >public List getChildList() < return childList; >public void setChildList(List childList) < this.childList = childList; >public String getDataValue() < return dataValue; >public void String(String dataValue) < this.dataValue = dataValue; >public static int getMaxNumberOfChildren() < return maxNumberOfChildren; >public static void setMaxNumberOfChildren(int maxNumberOfChildren) < NaryTreeNode.maxNumberOfChildren = maxNumberOfChildren; >public static int maxNumberOfChildren; // Equal to the n-arity; public NaryTreeNode(String dataValue) < this.dataValue = dataValue; childList = new ArrayList(maxNumberOfChildren); > public void addChild(NaryTreeNode childNaryTreeNode, int position) throws Exception < if (position >= maxNumberOfChildren - 1) < throw new Exception("Max number of childeren reached"); >else < System.out.println("this.children=" + this.childList); if (this.childList.get(position) != null) < // There is already a child node on this position; throw some error; >else < childNaryTreeNode.parentNode = this; this.childList.set(position, childNaryTreeNode); >> > >

In the above code snippet, the parentNode stores the parent information of the current node, childList stores the list of all the children of the current node and dataValue stores the information stored in the current node. TrieNode.java

public class TrieNode < final int ALPHABET_SIZE = 26; TrieNode[] trieChildList = new TrieNode[ALPHABET_SIZE]; boolean isEndOfWord; // used in implementation of Prefix Search, signifies the end of word. public TrieNode[] getTrieChildList() < return trieChildList; >public void setTrieChildList(TrieNode[] trieChildList) < this.trieChildList = trieChildList; >public boolean isEndOfWord() < return isEndOfWord; >public void setEndOfWord(boolean endOfWord) < isEndOfWord = endOfWord; >TrieNode() < isEndOfWord = false; for (int i = 0; i < ALPHABET_SIZE; i++) trieChildList[i] = null; >>

In the above code snippet, the trieChildList is the list of all the child nodes of the current node in Trie.

4. Applications of Node class

During the course of this article, we have seen various use-case featuring the Node class. Java Node class is actually being used as a generic name for any object template which is used in a building block for any non-sequential Data structure.

5. More articles

6. Download the source code

Last updated on Aug. 11th, 2021

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Implement Linked List in Java using Node class

Hey Folks,
I am back another tutorial of data structure. In this tutorial, we will learn how to implement a linked list in java using node class. It can also be done by importing class linked list from the library. But in this tutorial, we will learn to hard code the program.

Implementing Linked List in Java using Node Class

Firstly we create a class named Node. Every node consists of an address of the next element and its value. But the last node has null stored at its address as it is the last element.

This is how one node is connected to the other node. So we create a node class and it consists of two declarations. one is integer type data and the other is Node type next variable.

Creating Node.java file

The above code creates a block of memory. Where a part of it stores the address of next data and other part stores data.

Creating Linkedlist.java file

public class Linkedlist < Node head; public void insert(int data) < Node node=new Node(); node.data=data; node.next=null; if(head==null) < head=node; >else < Node n=head; while(n.next!=null) < n=n.next; >n.next=node; > > public void delete(int index) < if(index==0) < head=head.next; >else < Node n=head; Node n1=null; for(int i=0;in1=n.next; n.next=n1.next; System.out.println("n1" + n1.data); > > public void show() < Node node=head; while(node.next!=null) < System.out.println(node.data); node=node.next; >System.out.println(node.data); > public void insertAtStart(int data) < Node node=new Node(); node.data=data; node.next=head; head=node; >public void insertAt(int index,int data) < Node node=new Node(); node.data=data; node.next=head; Node n=head; for(int i=0;inode.next=n.next; n.next=node; > >

For inserting the node at the end we simply copy the address of the node to be added to the last node. And we make the newly added node as null. We can also add an element at the start. We replace the head node with a new node. And we put the address of the next node in our head node.

We can also add an element at the index of your choice with insertAt function. For deleting a node we can also write n.next=n.next.next. It automatically deletes an adjacent node. n.next represent the address of node and n.data gives us data stored in it.

Show function print data of the node until we encounter null value. Insert functions work is to add a node. It reaches to the position where we want to add the node by .next and adds.

Creating Runner.java file

//import java.util.LinkedList; public class Runner < public static void main(String[] args) < Linkedlist list=new Linkedlist(); list.insert(18); list.insert(7); list.insert(15); list.insertAtStart(25); list.insertAt(2,55); list.delete(2); list.show(); >>

Runner class is basically our driver class which connects all our files. It calls all the functions and resulted is printed here.

We make an object of LinkedList type named list. Then we call function one by one like object.functionName(value).
I hope it cleared your concepts. Feel free to ask your doubts in the comment section.

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