Advanced Java

Advanced Java” generally refers to a set of more complex and technical motifs in the Java programming language that go beyond the introductory generalities covered in introductory Java courses. These motifs are frequently used to make more sophisticated and robust operations.

Core Java

C java is primarily focused on building general applications. Java Standard Edition (J2SE) belongs to the Core Java category. Core Java mainly covers the concepts of object-oriented programming. The main pillars of OOP are encapsulation, inheritance, abstraction and polymorphism. They are next.

ADVANCED JAVA
ADVANCED JAVA

Data Types

As explained in the previous chapter, variables in Java must be of a specific data type.

Data types are divided into two groups.

Basic data types – including byte, short, int, long, float, double, boolean, and char.

Variables

Variables in Java are data containers that store data values ​​during Java program execution. Each variable is assigned a data type that determines the type and number of values ​​it can contain. A variable is the name of a memory location for data.

Arrays

An array is a collection of elements of a similar type with contiguous memory locations.

A Java array is an object containing elements of the same data type. besides this, the elements of an array are stored in contiguous areas of memory. A data structure that stores similar items. Java arrays can only store a fixed set of elements.

Control Statement’

Control statements inject the concept of changing the flow of code. When it comes to coding, you need to understand that computers execute code in a certain way, and most code is executed from top to bottom. From left to right, go to the first line until you reach the end of the code, then to the second line.

Methods

A method in Java is a set of statements that perform a specific task and return a result to the caller. A Java method can perform certain actions without returning anything. Java’s methods allow you to reuse code without retyping it. In Java, each method must be part of another class, not in a language like C, C, or Python.

classes

A class is a blueprint in the Java programming language from which a single object can be created. In Java, classes can be declared using the class keyword. Class members and functions are simply declared within the class. Classes are required to write Java programs. The object-oriented paradigm (OOP) allows users to describe objects in the real world.

Inheritance

Inheritance is an important pillar of object-oriented programming (OOP). A mechanism in Java that allows one class to inherit the functionality (fields and methods) of another class. Inheritance in Java means creating a new class based on an existing class. A class that inherits from another class can reuse the methods and fields of that class. You can also add new fields and methods to the current class.

Package

A package is a mechanism for grouping classes, interfaces, and subpackages of the same type and providing access control. Combine classes into a single whole.
Java already has many predefined packages available for programming.

Example: java.lang, java.io, java. util, etc.

Interface

It is similar to classes but contains only abstract methods.

By default, variables declared in interfaces are public, static, and final.

An interface is a mechanism for achieving complete abstraction.

The interface does not contain a constructor.

Exception Handling

Exception handling in Java is one of the powerful runtime error-handling mechanisms to keep your application flowing normally.

Multithreading

Multithreading in Java is the process of running two or more threads simultaneously to maximize CPU usage. A multi-threaded application runs two or more threads at the same time. Therefore, it is also called Concurrency in Java. Each thread runs parallel to each other. Multithreading saves memory by not allocating separate areas of memory. It also reduces context switching time between threads.

I/O

Java I/O stands for Java input and output. In other words, we can say that Java takes input from the user and then performs appropriate actions to produce output. In other words, Java I/O processes input and produces output.

Java Applet

Applets is a small Internet program written in Java, a programming language for the Internet, that can be downloaded to any computer. Applets can also work in HTML. Applets are usually embedded in the HTML pages of a website and can be run in a browser. When the applet arrives on the client, access to resources is restricted so that it can create graphical user interfaces and perform complex calculations without risk of viruses or data security breaches.

String Handling

The string is a sequence of characters. You can call an array of characters a string.

public class Main{
    
   public static void main(String args[]){
       char[] c={'j','a','v','a'};  
       String s1=new String(c);  
       
       String s2="java";
       
       System.out.println(s1);
       System.out.println(s2);
   }
}

Networking

Java networking is the concept of connecting two or more computing devices together so that they can share resources.

Java socket programming provides the ability to exchange data between different computing devices.

Advantages of Java Networking

  • Sharing resources
  • Centralize software management

Event handling

Any change in the state of an existing object is called an event. Event handlers are designed to listen for specific events and perform appropriate logic, and AWT components can listen for custom events and then register with the listeners required to properly handle the event. . In this section, you will learn about event handling in Java.

Introduction to AWT

The Java Abstract Window Toolkit (AWT) is an API for developing graphical user interface (GUI) or Windows applications in Java.

Java AWT components are platform-specific, so components are rendered according to the operating system view. AWT is heavy. That is, the component uses the resources of the underlying operating system (OS).

The java. awt package provides classes for the AWT APIs such as TextField, Label, TextArea, RadioButton, CheckBox, Choice, List, and more.

AWT controls

Each user interface considers three main aspects:

  • UI elements: These are the main visual elements that users will ultimately see and interact with. GWT provides a list of common elements that range from simple to complex and are covered in this guide.
  • Layout: Defines how user interface elements are arranged on the screen and provides the final look and feel of a graphical user interface (GUI). We will cover this in the Layout chapter.
  • Behavior: An event that is fired when a user interacts with a UI element. We will cover this in the event handling chapter.

Layout manager

A layout defines the format or order in which components should be placed in a container. A layout manager can be a class or component responsible for rearranging the components of a container according to the desired layout. A layout manager uses some kind of algorithm to automatically place controls in a window.

Menus

Menus provides a simple way for users to select one of several options. Other components that users can use to make selections include combo boxes, list boxes, radio buttons, spinners, and toolbars. If a menu item performs an action that overlaps with another menu item or toolbar button, you should read how to use the action along with this section.

Graphics

Graphics is an abstract class provided by Java AWT that is used to draw or draw components. It consists of various fields containing information such as the component to be drawn, font, colour, XOR mode, etc., and how to draw various shapes in the GUI component. Graphics is an abstract class and cannot be initialized directly. Objects of child classes can be obtained in two ways:

Java Swing

Swing has about four times as many user interface [UI] components as AWT and is part of the standard Java distribution. Given today’s application GUI requirements, AWT is a limited implementation that cannot fully provide the building blocks needed to develop the complex GUIs required for today’s commercial applications. The AWT component set has quite a few bugs and requires a lot of system resources compared to equivalent Swing resources. Netscape introduced the Internet Foundation Classes (IFC) library for use with Java. His classes are very popular among programmers creating GUIs for commercial applications.

Create a Swing Applet

The previous program example was a Swing-based application. The second type of program that commonly uses Swing is the applet. Swing applets extend JApplet, not Applet. JApplet is derived from Applet. Thus, JApplet contains all the features of an applet and adds support for Swing. JApplet is a top-level Swing container. As such, it includes the various panels previously described. As a result, all components are added to the JApplet content pane in the same way components are added to the JFrame content pane.

Pluggable Look and feel

A pluggable shape is a mechanism the Java Swing Widget Toolkit uses that allows the GUI shape to be changed at runtime.

Swing allows applications to customize the appearance of widgets by changing default widgets (via runtime parameters), deriving from existing widgets, creating new ones from scratch, or starting with J2SE 5.0 using the resizable synthesizer look and feel. can be defined. It consists of an XML properties file. Appearance can be changed at runtime.

Labels

Labels are the simplest of all AWT components. A label is a component that can contain non-editable text. Usually limited to single-line messages (tags, short notes, etc.). Commonly used to identify components. For example, in large GUIs, it can be difficult to determine the purpose of each component unless the GUI designer provides a label (that is, textual information indicating the purpose of each component).

Text fields

A TextField class object is a text component that allows users to enter and edit single-line text. Inherits the TextComponent class which further inherits the Component class.

When a key is entered into the text field (for example, a key is pressed, a key is released, or a key is pressed), an event is dispatched to the TextField. The KeyEvent is then dispatched to the registered KeyListener. This can also be done using ActionEvent. If an ActionEvent is enabled on a text field, you can press Return to fire the ActionEvent. Events are handled by the ActionListener interface.

Buttons

Buttons provide important functionality used to trigger events. A button is a control component that fires an event when clicked. While creating the button, we provide a label for the button.

The Button class extends the Component class and implements the Accessible interface.

Toggle buttons

A toggle button allows the user to change settings between the two states.

You can add a basic toggle button to your layout using the ToggleButton object. Android 4.0 (API level 14) introduces another type of toggle button called a toggle that provides a slider control that can be added using a Switch object. SwitchCompat is a version of the switch widget that works on devices using API 7.

Checkboxes

A checkbox, also known as the java.awt.Checkbox component, is a component used to present options that can be enabled (on = true) or disabled (off = false). It is typically used to present a set of options that the user can select independently or allow multiple selections.

Radio Buttons

Radio buttons provide a more user-friendly experience where you can choose just one from many options. A special kind of check box used to select only one option.

Scroll Panes

Scroll bars are used to create a scrollable view of a component. When screen size is limited, scroll bars are used to display large or dynamically resizable components.

Scroll Bars

The scroll bar class object is used to add horizontal & vertical scrollbars. This is my implementation of scrollbar. Inherits the Component class.

Lists

Lists in Java As mentioned previously, lists are interfaces that are child interfaces of the collections framework. You can store duplicate elements, and null values, loop in both directions and perform operations based on the index.

Menus

Menus provide a simple way for users to select one of several options. Other components that users can use to make selections include combo boxes, list boxes, radio buttons, spinners, and toolbars. If a menu item performs an action that overlaps with another menu item or toolbar button, you should read how to use the action along with this section.

Toolbars

A ToolBar container allows you to group other components, typically icon buttons, into rows or columns. JToolBar provides useful components for displaying frequently used actions or controls.

Layered Panes

Layered Panes class is used to add depth to pivot containers. It is used to provide a third dimension for positioning components and separating depth ranges into different layers.

Tabbed Panes

The Tabbed Pane class is used to switch between groups of components by clicking on a tab with a specified title or icon. Inherits the JComponent class.

Split Panes

You can produce split panes using colorful GUI libraries similar as Swing or JavaFX. Split panes allow you to divide a vessel into two or further resizable areas, generally with a separator that the stoner can drag to acclimate the size of each area.

Layouts

Layout managers in Java provide different strategies for arranging components within containers. Some commonly used layout managers include:

  • BorderLayout.
  • FlowLayout.
  • GridLayout.
  • GridBagLayout.
  • BoxLayout.

Windows

You can create windows using the JFrame class, which represents a top-level container. It provides the basic functionality required for a window, such as a title bar, borders, and controls for minimizing, maximizing, and closing the window. You can add other components to a JFrame to build the user interface of your application.

Inner Frames

Inner frames, also known as internal frames, are windows that can be embedded within another window, such as a desktop application or a document editor. In Java, you can create inner frames using the JInternalFrame class. They typically reside within a JDesktopPane container and can be moved, resized, and closed. Inner frames are useful for creating multiple document interfaces (MDI) or implementing a multi-window environment within a single application.

Dialog boxes

A dialogue box is a graphical component typically used to display errors or provide other information to the user. It is part of the three top-level containers that all Java graphical user interface (GUI) applications must have as root. Dialogs are created as part of a frame.

JDBC

JDBC or Java Database Connectivity is a Java API for connecting and querying databases. A Sun microsystem specification that provides standard abstractions (APIs or protocols) for Java applications to communicate with various databases. Provides the language with a standard for connecting to Java databases. Used to write programs that need to access databases. JDBC works with database drivers to access databases and spreadsheets. Enterprise data stored in relational databases (RDBs) can be accessed using JDBC APIs.

JDBC/ODBC Bridge

The JDBC-ODBC bridge allows applications written in the Java programming language to use the JDBC API with many existing ODBC drivers. The bridge itself is a JDBC-based driver (“JDBC Driver”) defined in the sun.jdbc.odbc.JdbcOdbcDriver class. The bridge defines the JDBC odbc subprotocol.

java.sql package

I have a relational database where data needs to be accessed multiple times. There is a java.sql package for various issues related to data handling in DBMS.

Connectivity to remote database

To establish connectivity to a remote database in advanced Java, you can make use of the Java Database Connectivity( JDBC) API. JDBC provides a standard set of classes and interfaces to interact with colourful databases.

Then is a step-by-step companion to connecting to a remote database in advanced Java using JDBC:

  1. Import the necessary JDBC packages.
  1. Load the database driver..
  1. Set up the database connection.
  1. Perform database operations.

Navigate Multiple Database Rows

To navigate through multiple rows recaptured from a database in advanced Java, you generally use a combination of JDBC( Java Database Connectivity) and SQL queries. Then is a step-by-step companion on how to achieve this:

  1. Establish a database connection.
  2. Execute a SELECT query.
  3. Retrieve the result set.
  4. Iterate through the result set.

Java Beans

A JavaBean is a Java class that must adhere to the following rules:

  • It must have a no-argument constructor.
  • Must be serializable.
  • You must provide methods for setting and getting property values, known as getters and setters.

Application Builder tools

A bean’s main purpose is to enable the visual composition of an application. You may have used or seen applications such as Visual Basic, Visual Age or Delphi. These tools are called visual application builders or simply build tools.

The bean developer kit (BDK)

The Beans Development Kit (or BDK) “is intended to support the development of JavaBeans components and serves as a standard reference base for both component developers and tool vendors.” It can be used as a standalone development tool (similar to the command-line tools provided by the Java2 SDK) or as a testing tool to verify that a component is working as intended. Recall the discussion of Java plug-ins and problems developers commonly face when implementing browser-based JVMs. To verify that a bean is actually working correctly, the BDK provides a good “health check”.

JAR files

JAR files are packaged in ZIP format, they can be used for tasks such as lossless data compression, archiving, unzipping, and unzipping archives. This is one of the most common uses of JAR files, and you can realize many of the benefits of JAR files by using only these basic features.

Introspection

Inspection is an important feature of the Java language. Introspection allows you to get internal information about a class at runtime. This information includes methods, fields, constructors, etc. One application of introspection is the development of applications using plug-ins. Applications can define the constructors, methods, and fields of the plug-in class and use this information at runtime. Another use for introspection is the creation of Java Beans and the development of Javadocs.

Developing a Simple Bean Using the BDK

This section provides examples showing how to develop simple components and connect them to other components through the BDK. A new component is the Colors Bean. It looks like a rectangle or ellipse filled with colour. The colour is chosen randomly when Bean starts running. You can change it by calling public methods. Each time the mouse clicks on a bean, a different random colour is chosen. There is one read/write boolean property that defines the shape.

Using Bound properties

you can use bound properties to implement the observer pattern and enable communication between objects. Bound properties allow you to notify registered listeners when a property’s value changes.

To use bound properties, you need to follow these steps:

  1. Define a property.
  2. Define listeners.
  3. Implement property change support.
  4. Update property setter.
  5. Implement listener logic.
  6. Register listeners.

Java Beans API

Java Bean API package java. lang. Beans contain a set of classes and interfaces that provide many of the features associated with creating beans based on the JavaBeans architecture. These classes are used by beans at runtime.

Session Beans

A session bean is a standalone Java Platform 2, Enterprise Edition (J2EE) server application that performs business operations for clients inside the server.

An interactive session occurs when a user and a computer exchange conversations. A session bean is similar to an interactive session in that it has only one client. When the client is terminated, the session bean is also terminated, as is the relationship between the session bean and the client.

Entiry Beans

An “object component” is a business-encoded persistent object that is an integral part of JAVA Enterprise Edition. It represents a persistent data object in the database. Beans and Entity JAVA Beans (EJBs) are widely known. They can persist independently or delegate them to containers. It is so powerful that it was widely used on WANs in JAVA EE 6 and earlier. The container is used to host the EJB service, and in case of container or server failure, the bean survives the failure because it is associated with a primary key in the database.

Enterprise Java beans (EJB)

Enterprise Java Beans (EJB) is one of several Java APIs for building standard enterprise software. EJBs are server-side programming elements that encapsulate an application’s business logic. The Enterprise Java Beans Web Repository provides a runtime domain for network-related programming elements, including machine reliability, Java Servlet (JSL) lifecycle management, transaction procedures, and other Web services. EJB enums are a subset of Java EE enums.

RMI (Remote Method Invocation)

RMI is an API that provides a mechanism for creating distributed applications in Java. RMI allows objects to call methods on objects running in another JVM.

RMI uses two entities: stubs and frameworks to provide remote communication between applications.

Java Servlets

It uses servlet technology to create web applications (located on the server side and generating dynamic web pages).

Servlet technology is powerful and extensible thanks to the Java language. Prior to Servlets, the Common Gateway Interface (CGI) scripting language was a common server-side programming language. However, this technique had many drawbacks. We have discussed these drawbacks below.

Servlet API basic

The javax.servlet and javax.servlet.http packages provide interfaces and classes to the Servlet API.

The javax. servlet package contains many interfaces and classes used by servlets or web containers. It is not protocol-specific.

life cycle of a servlet

The entire servlet lifecycle is managed by the servlet container, which uses the javax. servlet.Servlet interface to understand and manage servlet objects. So, before creating servlet objects, let’s first understand the servlet object life cycle to actually understand how the servlet container manages servlet objects.

Debugging servlets

Servlet debugging is a special case of debugging classes loaded through a custom class loader. Servlets run in the Java™ runtime environment of an application server, such as IBM® WebSphere Application Server for IBM I or IBM Integrated Web Application Server for i. There are several options for debugging servlets.

Thread-Safe HTTP Redirects

servlets can be used to handle HTTP requests and responses. When it comes to performing HTTP redirects, thread safety is an important consideration to ensure correct and dependable geste. Then is an overview of how you can apply thread-safe servlets for handling HTTP redirects

  1. Synchronization.
  2. Atomic operations.
  3. Use local variables.
  4. Redirect using response.sendRedirect().

Cookies

Cookies represent information in the form of key-value pairs. This information is sent from the server to the client computer as part of the response. Allows the client to provide it to the server as part of a subsequent request. Cookies provide a simple mechanism for storing user information between requests.

Java Server Pages (JSP)

Java Server Pages (JSP) is a server-side programming technology that allows you to create dynamic, platform-independent methods for building web applications. JSPs can access the entire Java API suite, including the JDBC API for accessing enterprise databases. This tutorial teaches you how to develop web applications using Java Server Pages in simple and easy steps.