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(Affiliated to JNTUH, Hyderabad, Approved by AICTE - Accredited by NBA & NAAC – ‘A’ Grade - ISO 9001:2015 Certified) Maisammaguda, Dhulapally (Post Via. Hakimpet), Secunderabad – 500100, Telangana State, INDIA. [JAVA PROGRAMMING] Page 1
II Year B.Tech IT – II Sem L T /P/D C 4 /-/- 4 (R18A0509)JAVA PROGRAMMING Objectives: This subject aims to introduce students to the Java programming language. Upon successful completion of this subject, students should be able to create Java programs that leverage the object- oriented features of the Java language, such as encapsulation, inheritance and polymorphism; use data types, arrays and other data collections; implement error-handling techniques using exception handling, create and event-driven GUI using Swing components. UNIT‐I Java Programming‐ History of Java, comments, Data types, Variables, Constants, Scope and Lifetime of variables, Operators, Type conversion and casting, Enumerated types, Control flow‐ block scope, conditional statements, loops, break and continue statements, arrays, simple java stand alone programs, class, object, and its methods constructors, methods, static fields and methods, access control, this reference, overloading constructors, recursion, exploring string class, garbage collection UNIT – II Inheritance – Inheritance types, super keyword, preventing inheritance: final classes and methods.. Polymorphism – method overloading and method overriding, abstract classes and methods. Interfaces‐ Interfaces Vs Abstract classes, defining an interface, implement interfaces, accessing implementations through interface references, extending interface, inner class. Packages‐ Defining, creating and accessing a package, importing packages. UNIT‐III Exception handling‐Benefits of exception handling, the classification of exceptions ‐ exception hierarchy, checked exceptions and unchecked exceptions, usage of try, catch, throw, throws and finally, creating own exception subclasses. Multithreading – Differences between multiple processes and multiple threads, thread life cycle, creating threads, interrupting threads, thread priorities, synchronizing threads, inter‐thread communication, producer consumer problem. UNIT‐IV Collection Framework in Java – Introduction to java collections, Overview of java collection framework, Commonly used collection classes‐ Array List, Vector, Hash table, Stack, Lambda Expressions. Files‐ Streams‐ Byte streams, Character streams, Text input/output, Binary input/output, File management using File class. Connecting to Database – JDBC Type 1 to 4 drivers, Connecting to a database, querying a database and processing the results, updating data with JDBC,Data Access Object (DAO). UNIT‐V GUI Programming with Swing ‐ The AWT class hierarchy, Introduction to Swing, Swing Vs AWT, Hierarchy for Swing components, Overview of some Swing components – Jbutton, JLabel, JTextField, JTextArea, simple Swing applications, Layout management – Layout manager types – border, grid and flow Event Handling‐ Events, Event sources, Event classes, Event Listeners, Delegation event model, Examples: Handling Mouse and Key events, Adapter classes. [JAVA PROGRAMMING] Page 2
UNIT I Java Programming‐ History of Java, comments, Data types, Variables, Constants, Scope and Lifetime of variables, Operators, Type conversion and casting, Enumerated types, Control flow‐ block scope, conditional statements, loops, break and continue statements, arrays, simple java stand alone programs, class, object, and its methods constructors, methods, static fields and methods, access control, this reference, overloading constructors, recursion, exploring string class, garbage collection Introduction Everywhere you look in the real world you see objects—people, animals, plants, cars, planes, buildings, computers and so on. Humans think in terms of objects. Telephones, houses, traffic lights, microwave ovens and water coolers are just a few more objects. Computer programs, such as the Java programs you’ll read in this book interacting software objects. We sometimes divide objects into two categories: animate and inanimate. Animate objects are ―alive‖ theyinmovesomearound andsensedothings. —Inanimate objects, on the other hand, do not move on their own .Objects of both types, however, have some things in common. They all have attributes (e.g., size, shape, color and weight), and they all exhibit behaviors (e.g., a ball rolls, bounces, inflates and deflates; a baby cries, sleep crawls, walks and blinks; a car accelerates, brakes and turns; a towel absorbs water). We will study the kinds of attributes and behaviors that software objects have. Humans learn about existing objects by studying their attributes and observing their behaviors. Different objects can have similar attributes and can exhibit similar behaviors. Comparisons can be made, for example, between babies and adults and between humans and chimpanzees. Object-oriented design provides a natural and intuitive way to view the software design process—namely, modeling objects by their attributes and behaviors just as we describe real- world objects. OOD also models communication between objects. Just as people send messages to one another (e.g., a sergeant commands a soldier to stand at attention), objects also communicate via messages. A bank account object may receive a message to decrease its balance by a certain amount because the customer has withdrawn that amount of money. Object-Oriented: Although influenced by its predecessors, Java was not designed to be source-code compatible with any other language. This allowed the Java team the freedom to design with a blank slate. One outcome of this was a clean, usable, pragmatic approach to objects. Borrowing liberally from many seminal object-software environments of the last few decades, Java manages to strike a balance between the purist’s ―everything is of my way‖ model. The object model in Java i such as integers, are kept as high-performance non objects. [JAVA PROGRAMMING] Page 4
OOD encapsulates (i.e., wraps) attributes and operations (behaviors) into objects, an object’s attributes and operations are intim information hiding. This means that objects may know how to communicate with one another across well-defined interfaces, but normally they are not allowed to know how other objects are implemented ,implementation details are hidden within the objects themselves. Wecan drive a car effectively, for instance, without knowing the details of how engines, transmissions, brakes and exhaust systems work internally—as long as we know how to use the accelerator pedal, the brake pedal, the wheel and so on. Information hiding, as we will see, is crucial to good software engineering. Languages like Java are object oriented. Programming in such a language is called object-oriented programming (OOP), and it allows computer programmers to implement an object-oriented design as a working system. Languages like C, on the other hand, are procedural, so programming tends to be action oriented. In C, the unit of programming is the function. Groups of actions that perform some common task are formed into functions, and functions are grouped to form programs. In Java, the unit of programming is the class from which objects are eventually instantiated (created). Java classes contain methods (which implement operations and are similar to functions in C) as well as fields (which implement attributes). Java programmers concentrate on creating classes. Each class contains fields, and the set of methods that manipulate the fields and provide services to clients (i.e., other classes that use the class). The programmer uses existing classes as the building blocks for constructing new classes. Classes are to objects as blueprints are to houses. Just as we can build many houses from one blueprint, we can instantiate (create) many objects from one class. Classes can have relationships with other classes. For example, in an object-oriented design of a bank, the ―bank teller‖ class needs to relate ―safe‖ class, and so on. These relationships Packaging software as classes makes it possible for future software systems to reuse the classes. Groups of related classes are often packaged as reusable components. Just as realtors often say that the three most important factors affecti location,‖ people in the software community affecting the future of software development are ―reuse, classes when building new classes and programs saves time and effort.Reuse also helps programmers build more reliable and effective systems, because existing classes and components often have gone through extensive testing, debugging and performance tuning. Indeed, with object technology, you can build much of the software you will need by combining classes, just as automobile manufacturers combine interchangeable parts. Each new class you create will have the potential to become a valuable software asset that you and other programmers can use to speed and enhance the quality of future software development efforts. [JAVA PROGRAMMING] Page 5
Drawback: It does not model real world problems very well, because functions are action oriented and do not really corresponding to the elements of the problem. Characteristics of POP: Emphasis is on doing actions. Large programs are divided into smaller programs known as functions. Most of the functions shared global data. Data move openly around the program from function to function. Functions transform data from one form to another. Employs top-down approach in program design. OOP: OOP allows us to decompose a problem into a number of entities called objects and then builds data and methods around these entities. DEF: OOP is an approach that provides a way of modularizing programs by creating portioned memory area for both data and methods that can used as templates for creating copies of such modules on demand. That is ,an object a considered to be a partitioned area of computer memory that stores data and set of operations that can access that data. Since the memory partitions are independent, the objects can be used in a variety of different programs without modifications. OOP Chars: Emphasis on data. Programs are divided into what are known as methods. Data structures are designed such that they characterize the objects. Methods that operate on the data of an object are tied together. Data is hidden. Objects can communicate with each other through methods. Reusability. Follows bottom-up approach in program design.
Organization of OOP: Evolution of Computing and Programming : Computer use is increasing in almost every field of endeavor. Computing costs have been decreasing dramatically due to rapid developments in both hardware and software technologies. Computers that might have filled large rooms and cost millions of dollars decades ago can now be inscribed on silicon chips smaller than a fingernail, costing perhaps a few dollars each. Fortunately, silicon is one of the most abundant materials on earth it is an ingredient in common sand. Silicon chip technology has made computing so economical that about a billion general-purpose computers are in use worldwide, helping people in business, industry and government, and in their personal lives. The number could easily double in the next few years. Over the years, many programmers learned the programming methodology called structured programming. You will learn structured programming and an exciting newer methodology, object-oriented programming. Why do we teach both? Object orientation is the key programming methodology used by programmers today. You will create and work with many software objects in this text. But you will discover that their internal structure is often built using structured-programming techniques. Also, the logic of manipulating objects is occasionally expressed with structured programming. Language of Choice for Networked Applications : Java has become the language of choice for implementing Internet-based applications and software for devices that communicate over a network. Stereos and other devices in homes are now being networked together by Java technology. At the May 2006 JavaOne conference, Sun announced that there were one billion java-enabled mobile phones and hand held devices! Java has evolved rapidly into the large-scale applications arena. It’s the preferred-wide programming needs. Java has evolved so rapidly that this seventh edition of Java How to Program was published just 10 years after the first edition was published. Java has grown so large that it has two other editions. The Java Enterprise Edition (Java EE) is geared toward developing large-scale, distributed networking applications and web-based applications. The Java Micro Edition (Java ME) is geared toward developing applications for small, memory constrained devices, such as cell phones, pagers and PDAs. method method method
Concepts of classes and objects: Class Fundamentals Classes have been used since the beginning of this book. However, until now, only the most rudimentary form of a class has been used. The classes created in the preceding chapters primarily exist simply to encapsulate the main( ) method, which has been used to demonstrate the basics of the Java syntax. Thus, a class is a template for an object, and an object is an instance of a class. Because an object is an instance of a class, you will often see the two words object and instance used interchangeably. The General Form of a Class When you define a class, you declare its exact form and nature. You do this by specifying the data that it contains and the code that operates on that data. A class is declared by use of the class keyword. The classes that have been used up to this point are actually very limited examples of its complete form. Classes can (and usually do) get much more complex. The general form of a class definition is shown here: class classname { type instance- variable1 ; type instance-variable2 ; // ... type instance-variableN ; type methodname1 ( parameter-list ) { // body of method } type methodname2 (p arameter-list ) { // body of method } // ... type methodnameN ( parameter-list ) { // body of method } } The data, or variables, defined within a class are called instance variables. The code is contained within methods. Collectively, the methods and variables defined within a class are called members of the class. In most classes, the instance variables are acted upon and accessed by the methods defined for that class. Thus, it is the methods that de can be used. Declaring Objects As just explained, when you create a class, you are creating a new data type. You can use this type to declare objects of that type. However, obtaining objects of a class is a two-step process. First, you must declare a variable of the class type. This variable does not define an object. Instead, it is simply a variable that can refer to an object. Second, you must acquire an actual, physical copy of the object and assign it to that variable. You can do this using the new operator. The new operator dynamically allocates (that is, allocates at run time) memory for an object and returns a reference to it. This reference is, more or less, the address in memory of the object allocated by new. Ex: Box mybox = new Box(); This statement combines the two steps just described. It can be rewritten like this to show each step more clearly:
Box mybox; // declare reference to object mybox = new Box(); // allocate a Box object A Closer Look at new As just explained, the new operator dynamically allocates memory for an object. It has this general form: class-var = new classname ( ); Here, class-var is a variable of the class type being created. The classname is the name of the class that is being instantiated. The class name followed by parentheses specifies the constructor for the class. A constructor defines what occurs when an object of a class is created. Constructors are an important part of all classes and have many significant attributes. Most real-world classes explicitly define their own constructors within their class definition. However, if no explicit constructor is specified, then Java will automatically supply a default constructor. This is the case with Box. HISTORY OF JAVA Java was conceived by James Gosling, Patrick Naughton, Chris Warth, Ed Frank, and Mike Sheridan at Sun Microsystems, Inc. in 1991. It took 18 months to develop the first Working version. This language was initially Between the initial implementation of Oak in the fall of 1992 and the public Announcement of Java in the spring of 1995, many more people contributed to the designand evolution of the language. Bill Joy, Arthur van Hoff, Jonathan Payne, Frank Yellin, and Tim Lind Holm were key contributors to the maturing of the original prototype. The trouble With C and C++ (and most other languages) is that they are designed to be compiled For a specific target. Although it is possible to compile a C++ program for just about Any type of CPU, to do so requires a full C++ compiler targeted for that CPU. The Problem is that compilers are expensive and time-consuming to create. An easier—and more cost- efficient—solution was needed. In an attempt to find such a solution,Gosling and others began work on a portable, platform-independent language thatcould be used to produce code that would run on a variety of CPUs under differing Environments. This effort ultimately led to the creation of Java.
Multithreaded Java was designed to meet the real-world requirement of creating interactive, networked programs. To accomplish this, Java supports multithreaded programming, which allows you to write programs that do many things simultaneously. The Java run-time system comes with an elegant yet sophisticated solution for multiprocess .synchronization that enables you to construct smoothly running interactive systems. Architecture-Neutral A central issue for the Java designers was that of code longevity and portability. One of the main problems facing programmers is that no guarantee exists that if you write a program today, it will run tomorrow—even on the same machine. Operating system up grades, processor upgrades, and changes in core system resources can all combine to make a program malfunction. The Java designers made several hard decisions in the Java language and the Java Virtual Machine in an attempt to alter this situation forever.‖ To a great extent, this goal was accomplished. Interpreted and High Performance As described earlier, Java enables the creation of cross-platform programs by compiling into an intermediate representation called Java bytecode. This code can be interpreted on any system that provides a Java Virtual Machine. Most previous attempts at cross platform solutions have done so at the expense of performance. Other interpreted systems, such as BASIC, Tcl, and PERL, suffer from almost insurmountable performance deficits. Java, however, was designed to perform well on very low-power CPUs. Distributed Java is designed for the distributed environment of the Internet, because it handles TCP/IP protocols. In fact, accessing a resource using a URL is not much different from accessing a file. The original version of Java (Oak) included features for intra address-space messaging. This allowed objects on two different computers to execute procedures remotely. Java revived these interfaces in a package called Remote MethodInvocation ( RMI ). This feature brings an unparalleled level of abstraction to client/server programming. Dynamic Java programs carry with them substantial amounts of run-time type information that is used to verify and resolve accesses to objects at run time. This makes it possible to dynamically link code in a safe and expedient manner. This is crucial to the robustness of the applet environment, in which small fragments of bytecode may be dynamically updated on a running system. DATA TYPES Java defines eight simple (or elemental) types of data: byte , short , int , long , char , float , double , and boolean. These can be put in four groups: Integers This group includes byte , short , int , and long , which are for whole valued signed numbers. Floating-point numbers This group includes float and double , which represent numbers with fractional precision. Characters This group includes char , which represents symbols in a character set, like letters and numbers. Boolean This group includes boolean , which is a special type for representing true/false values.
Integers Java defines four integer types: byte , short , int , and long. All of these are signed, positive and negative values. Java does not support unsigned, positive-only integers. Many other Computer languages, including C/C++, support both signed and unsigned integers. Name Width Range long 64 – 9,223,372,036,854,775,808 to 9,223,372,036,854,775, int 32 – 2,147,483,648 to 2,147,483, short 16 – 32,768 to 32, byte 8 – 128 to 127 byte The smallest integer type is byte. This is a signed 8 - bit type that has a range from – 128to
Declaring a Variable In Java, all variables must be declared before they can be used. The basic form of a variable declaration is shown here: type identifier [ = value ][, identifier [= value ] ...] ; The type is one of Java’s atomic types, or the nam interface types are discussed later in Part I of this book.) The identifier is the name of the variable. Here are several examples of variable declarations of various types. Note that some include an initialization. int a, b, c; // declares three ints, a, b, and c. int d = 3, e, f = 5; // declares three more ints, initializing // d and f. byte z = 22; // initializes z. double pi = 3.14159; // declares an approximation of pi. char x = 'x'; // the variable x has the value 'x'. The Scope and Lifetime of Variables So far, all of the variables used have been declared at the start of the main( ) method. However, Java allows variables to be declared within any block. As explained in Chapter 2, a block is begun with an opening curly brace and ended by a closing curlybrace. A block defines a scope. Thus, each time you start a new block, you are creating a new scope. As you probably know from your previous programming experience, a scope determines what objects are visible to other parts of your program. It also determines the lifetime of those objects. Most other computer languages define two general categories of scopes: global and local. However, these traditional scopes do not fit scope defined by a method begins with its opening curly brace. To understand the effect of nested scopes, consider the following program: // Demonstrate block scope. Arrays An array is a group of like-typed variables that are referred to by a common name. Arrays of any type can be created and may have one or more dimensions. A specific elementin an array is accessed by its index. Arrays offer a convenient means of grouping related information. One-Dimensional Arrays A one-dimensional array is, essentially, a list of like-typed variables. To create an array, you first must create an array variable of the desired type. The general form of a one dimensional array declaration is type var-name [ ]; Here, type declares the base type of the array. The base type determines the data type of each element that comprises the array. // Demonstrate a one-dimensional array. class Array { public static void main(String args[]) { int month_days[]; month_days = new int[12]; month_days[0] = 31; month_days[1] = 28;
month_days[2] = 31; month_days[3] = 30; month_days[4] = 31; month_days[5] = 30; month_days[6] = 31; month_days[7] = 31; month_days[8] = 30; month_days[9] = 31; month_days[10] = 30; month_days[11] = 31; System.out.println("April has " + month_days[3] + " days."); } } Multidimensional Arrays In Java, multidimensional arrays are actually arrays of arrays. These, as you mightexpect, look and act like regular multidimensional arrays. However, as you will see there are a couple of subtle differences. To declare a multidimensional array variable,specify each additional index using another set of square brackets. For example, the following declares a two-dimensional array variable called twoD. int twoD[][] = new int[4][5]; This allocates a 4 by 5 array and assigns it to twoD. Internally this matrix is implemented as an array of arrays of int. // Demonstrate a two-dimensional array. class TwoDArray { public static void main(String args[]) { int twoD[][]= new int[4][5]; int i, j, k = 0; for(i=0; i<4; i++) for(j=0; j<5; j++) { twoD[i][j] = k; k++; } for(i=0; i<4; i++) { for(j=0; j<5; j++) System.out.print(twoD[i][j] + " "); System.out.println(); } } } This program generates the following output: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 As stated earlier, since multidimensional arrays are actually arrays of arrays, the length of each array is under your control. For example, the following program creates a two dimensional array in which the sizes of the second dimension are unequal.
The outcome of these operations is a boolean value. The relational operators are most frequently used in the expressions that control the if statement and the various loop statements. The Assignment Operator You have been using the assignment operator since Chapter 2. Now it is time to take a formal look at it. The assignment operator is the single equal sign, =. The assignment operator works in Java much as it does in any other computer language. It has this general form: var = expression ; Here, the type of var must be compatible with the type of expression. The assignment operator does have one interesting attribute that you may not be familiar with: it allows you to create a chain of assignments. For example, consider this fragment: int x, y, z; x = y = z = 100; // set x, y, and z to 100 This fragment sets the variables x , y , and z to 100 using a single statement. This works because the = is an operator that yields the value of the right-hand expression. Thus, the value of z = 100 is 100, which is then assigned to y , which in turn is assigned to x. Using a ―cha assignment‖ is an easy way to set a group of The? Operator Java includes a special ternary (three-way) operator that can replace certain types ofif- then-else statements. This operator is the? , and it works in Java much like it doesin C, C++, and C#. It can seem somewhat confusing at first, but the? can be used very effectively once mastered. The? has this general form: expression1? expression2 : expression Here, expression1 can be any expression that evaluates to a boolean value. If expression1 is true , then expression2 is evaluated; otherwise, expression3 is evaluated. The result of the? operation is that of the expression evaluated. Both expression2 and expression3 are required to return the same void type,. which can’t be CONTROL STATEMENTS if The if statement was introduced in Chapter 2. It is examined in detail here. The if statement is Java’s conditionalprogrambranchexecution state through two different paths. Here is the general form of the if statement: if ( condition ) statement1 ; else statement2 ; Here, each statement may be a single statement or a compound statement enclosed in curly braces (that is, a block ). The condition is any expression that returns a boolean value. The else clause is optional. int a, b; // ... if(a < b) a = 0; else b = 0; The if-else-if Ladder A common programming construct that is based upon a sequence of nested if s is the if-else-if ladder. It looks like this: if( condition ) statement; else if (condition )
statement ; else if( condition ) statement ; ... else statement ; switch The switch statement is Java’s multiway branch dispatch execution to different parts of your code based on the value of an expression. As such, it often provides a better alternative than a large series of if-else-if statements. Here is the general form of a switch statement: switch ( expression ) { case value1 : // statement sequence break; case value2 : // statement sequence break; ... case valueN : // statement sequence break; default: // default statement sequence } The expression must be of type byte , short , int , or char ; each of the values specified in the case statements must be of a type compatible with the expression. Each case value must be a unique literal (that is, it must be a constant, not a variable). Duplicate case values are not allowed Iteration Statements Java’s iteration for , while , andstatements do-while .Thesestatementsarecreate what we commonly call loops. As you probably know, a loop repeatedly executes the same set of instructions until a termination condition is met. As you will see, Java has a loop to fit any programming need. While The while loop is Java’sfundamentalloopingmoststatement. It repeats a statement or block while its controlling expression is true. Here is its general form: While ( condition ) { // body of loop } The condition can be any Boolean expression. The body of the loop will be executed as long as the conditional expression is true. When condition becomes false, control passes to the next line of code immediately following the loop. The curly braces are unnecessary if only a single statement is being repeated. do-while As you just saw, if the conditional expression controlling a while loop is initially false, then the body of the loop will not be executed at all. However, sometimes it is desirable to execute the body of a while loop at least once, even if the conditional expression is false to begin with.
