For instance, in developing a library application system, we would have considered processes such as the checking in an d out of books, making reservations of books, cataloging of books, and so on. Problem solving would involve the analysis of these processes in terms of the procedural tasks carried out and the production of a system whose representation is based on the procedural flow of the processes.

Object-oriented programming, on the other hand, models objects and their in- teractions in the problem space and the production of a system based on these objects and their interactions. Since the real-world problem domain is characterized by objects and their in- teractions, a software application developed using the object-oriented programming approach will result in the production of a computer system that has a closer repre- sentation of the real-world problem domain than would be the case if the procedural programming approach is used.

There are two persons, Benjamin and his wife, Bambie. They are customers of HomeCare, a company dealing in luxurious furni- ture. HomeCare sells a variety of sofa sets. Each sofa set is labeled with an identifi- cation number and a price tag. After viewing the sofa sets for an hour, Benjamin and Bambie decide to purchase a green leather 5-seater set. They approach Sean, a sales- person, to place their order. Can you please have it sent to me by next Wednesday? It con- tains information such as the type of sofa set a green leather, 5-seater set and the date of delivery next Wednesday.

This information is known as the parameters of the takeOrder message. We can represent the interaction between Benjamin and Sean graphically using Figure result takeOrder Benjamin Sean Figure Interaction between Benjamin and Sean. In fact, most of the time, customers do not know how a salesperson has satisfied their orders.

We will deliver the goods on Wednesday between 10 am to 11 am to the address indicated. Thank you for your order. He maintains his responsibility by applying a set of operations: 1. He determines if the requested date for delivery is a suitable date. Finally, he informs Benjamin the result of his request. Introduction 3 1. For instance, Benjamin and Sean are objects that interact by sending messages. Benjamin is thus a message-sending object, while Sean is a message-receiving object.

Alternatively, we can label Benjamin as a sender and Sean as a receiver. The takeOrder request from Benjamin to Sean is an example of a message. It may have additional, accompanying information known as parameters or argu- ments of the message.

Each valid message corresponds to a method that Sean uses to fulfill his responsibility to Benjamin. An invalid message, on the other hand, is one that the receiver does not have the capability to respond to, that is, the receiver does not have a corresponding method to match the message. For example, if Benjamin had requested a discount on the price, his request would have been rejected because Sean, being a salesperson, would not have the capability or a corresponding method to respond to the message.

A method contains a number of operations detailing how Sean is to satisfy the demand Benjamin put on Sean through the request.

Figure summarizes the relationships of these terms. Message Arguments Method takeOrder sofa type, who, address, delivery date Benjamin result Sean Object Object Figure Object interactions in object-oriented programming terms. While Benjamin may know what Sean can do through his methods, he may not know how Sean does them.

This is an important principle of object-oriented pro- gramming known as information hiding: the sender of a message does not know how a receiver is going to satisfy the request in the message. These concepts are thus suitable for simulating actual object interactions in real-world situations. The Simula programming language was designed in the early s to provide simulation abilities using object-oriented concepts.

It is a unique language in that, being a new language at that time, it was able to attract a lot of interest from the computing community. Within two years after Java was launched, there were an estimated , Java programmers and over books on Java programming. There are a few possible reasons for the phenomenal interest in Java. Java is implemented via part compilation and subsequent execution on an interpreter implemented in software.

Java applications are therefore object code portable as long as a Java virtual machine is implemented for the target machine. In relation to the Internet, Java applets have given rise to a new generation of distributed applications with low software distribution and maintenance costs. While the object-oriented programming framework promotes reusability of software and code, this very practice has been demonstrated in the rich set of class libraries seen in the Java language.

The Java foundation class libraries provide for windowing and graphical user interface programming, network communications, and multimedia facilities. Together, they demonstrate the practical and productive work done in Java. Distinguish the programming approach used in procedural programming and object-oriented programming. Discuss the validity of the following statement: The object-oriented pro- gramming approach is ideal for simulating real-world problems.

Another concept closely associated with the concept of objects is class. In object-oriented programming, a class is a definition template for structuring and creating objects.

In this chapter, we will discuss the concept of object, message, method and class and how these concepts are used in a computer model. Now, meet Bernie, another customer at HomeCare. As customers of HomeCare, Benjamin and Bernie share some similar information.

For example, both have a name, an address, and a budget—information that is relevant when describing customers. This information is known as object attributes. An object attribute definition allows for objects to have independent attribute values. Besides attributes, Benjamin and Bernie also exhibit some behavior typical of a customer.

For instance, Benjamin and Bernie execute a method when making a purchase. Let us call this method purchase. The method purchase is made up of a set of operations that Benjamin and Bernie would use to send a purchase request to a salesperson. Note that both objects share a common definition of attributes and methods. In fact, all customers of HomeCare share the same set of attribute and method definitions. They all have attributes name, address and budget, and methods purchase and getBudget.

In defining these objects, a common definition known as class is used. A class is a definition template for structuring and creating objects with the same attributes and methods. Benjamin and Bernie, being customers of HomeCare, can therefore be defined by a class called Customer as follows: Class Customer Attributes: name address budget Methods: purchase {send a purchase request to a salesperson} getBudget {return budget} One major difference between objects and class is in the way attributes and methods are treated in objects and classes.

A class is a definition about objects; the attributes and methods in a class are thus declarations that do not contain values. However, objects are created instances of a class.

Each has its own attributes and methods. The values of the set of attributes describe the state of the objects. Let us now examine the salespersons.

Salespersons also have attributes and methods. Sean and Sara are two salespersons at HomeCare. They are thus capable of a behavior typical of a salesperson, for example, taking orders from customers. To fulfill their role as salespersons in a purchase transaction, Sean and Sara perform a method.

Like the customers, their definition can be described by a class called SalesPerson with the following representation: Class SalesPerson Attributes: name Methods: takeOrder { check with warehouse on stock availability check with warehouse on delivery schedule if ok then {instruct warehouse to deliver stock address, date return ok} else return not ok } Note that the definition of the SalesPerson class is different from the Customer class since customers and salespersons behave differently—customers make orders and salespersons take orders.

A message is a method call from a message-sending object to a message-receiving object. A message- sending object is a sender while a message-receiving object is a receiver.

Additional information, known as arguments, may accompany a method call. Such para- meterization allows for added flexibility in message passing. The set of methods collectively defines the dynamic behavior of an object.

An object may have as many methods as required. Earlier we saw that Benjamin sent a message to Sean when Benjamin wanted to buy a sofa set.

takeOrder "Benjamin", "sofa", "1, Robinson Road", "12 November" } getBudget {return budget} The message Sean. Only valid messages are executed by the receiver.

The takeOrder message is valid because Sean has a corresponding method and the required arguments who, stock, address, date are supplied with the message. If both conditions are satisfied, Sean will instruct the Warehouse object to arrange for delivery. How Sean carries out the method is known only to Sean. Neither Benjamin nor the other customers know how Sean does it. For example, to check on the stock and delivery schedule with the warehouse, Sean may have called the warehouse over the phone or he may have checked the information against a list he had gotten from the warehouse.

What Benjamin knows of Sean is that Sean is capable of responding to his request since his message to Sean is acceptable by Sean. A message-receiving object is thus a server to a message-sending object and the message-sending object is thus a client of the server. takeOrder send Sean ok Benjamin Figure Object communication process. In any object communication, there are at least a client and a server.

The client sends a message to request a server to perform a task. In sending a message to the ware- house, Sean is said to be the client and the warehouse is said to be the server. Benjamin, Sean, and the warehouse are three objects involved in a communi- cation process. Benjamin is the initiator, with Sean and the warehouse as partners in the communication process.

Figure depicts a typical communication process amongst objects. Instances of Customer objects are created from a Customer class and SalesPerson objects from a SalesPerson class. Created object instances are individuals with their own state. To illustrate, let us consider the example of counters. A counter is a device that keeps account of the number of times an event has occurred. It has two buttons: an initialize button that resets the counter to 0, and an add button that adds 1 to its present number.

Figure shows a counter with a number initialize add 10 Figure A counter. Suppose a new object is created from the Counter class. Although the new Counter object would have the same definition of attributes and methods as the previous three counters, its attribute value may not be the same as the other counters. This suggests that the state of the counters may be different from one another. Consider the scenario of buying flowers from a florist.

Outline the objects in such a transaction together with the messages exchanged. Given a class definition Rectangle below, describe the structure of any 3 instances of Rectangle.

class Rectangle { Attributes: length width Methods: getLength { return length } getWidth { return width } draw { How would you implement the concept of class and method in a non-object-oriented programming language such as COBOL, Pascal or C?

Define using the following structure a class definition for cars. A car can also return to its relative location. The starting location is a value 0. class Car { Attributes Distinguish between a client and a server. In this chapter, we see how the Java programming language is used to construct our object model of the problem domain. We have seen that objects may have diverse behavior and that it is more convenient to specify objects via classification, that is, class constructs.

Before examining class definitions for user-specified objects, we should be mindful that Java also provides primitive values from which other bigger objects may be described in terms of and constructed from. For example, a complex number may be seen as being comprised of two numbers representing the real and imaginary parts.

The primitive types byte, short, int and long defined in the Java language allow for the representation of discrete integer values of widths 8, 16, 32, and 64 bits, respectively. These in turn correspond to the representation of numeric ranges — to , — to , — to , and — to , respectively. The primitive types float and double allow for the representation of single and double precision floating-point real values with representational widths of 32 and 64 bits, respectively.

The adopted IEEE standard includes both positive and negative sign-magnitude numbers, both positive and negative zeros and infinities, and unique not-a-number representations. Similarly, values of type double have the similar form s·m·2e, but m is a positive integer less than , and e is an integer between — and A class construct in Java consists of the class keyword followed by the class name and braces { } which delimit the declaration of attributes and methods for its in- stances.

The Counter class introduced in Chapter 2 would have the following form in Java: class Counter { attribute and method declarations } Object attributes are, in turn, either nested component objects or primitive types used to represent the object.

An instance method manipulates the object by altering its attribute values. This further implies that an attribute in one instance is independent from that in another instance. In the same vein, a method manipulates object attributes in the same instance. This occurs when a method is invoked and the corresponding code in its body is executed. In our recent example, invoking the add method of an object will increment the corresponding number attribute. As such, appropriate storage may be set aside for these values.

There is another subtle advantage of typing in programming languages: the val- ues associated with the variable also imply what operations are valid and applicable.

For example, multiplication and division applies to numeric values but not to charac- ter values. Thus, the language compiler may flag multiplication and division of char- acter values as erroneous. All variables in Java are typed, allowing the compiler to verify during compila- tion that operations on the object associated with the variable are legitimate.

The method signature portion, such as void add in the Counter example, has the generic form below, where m is the method name, T its return type, with Rn and pn being parameter types and names, respectively n being the number of parame- ters : T m R1 p1, R2 p2, Rn pn We have seen that a method named m is invoked to correspond to a message m sent to the object. Consequently, the object may return a result to the message sender.

The type of this value is denoted by T. If no result needs be returned, the keyword void is used instead. The formal parameters p1, p2…pn contain the additional values sent together with the message.

They have corresponding types R1, R2…Rn, and are used by the compiler to verify that the correct parameters are supplied for each method invoca- tion. Any number of formal parameters may be specified, but the number of actual parameters in a message must match those originally specified in the method signa- ture. The implementation of a method consists of a block of statements surrounded by { }. In the case of the add method of our Counter example, it increments the variable number.

A block consists of declarations of any local variable, expressions and control-flow con- structs. These will be discussed in detail in following sections. In the slightly expanded version of the Counter class below, an extra initialize method has been added to re-initialize the Counter value so that counting can be easily restarted.

This allows instances to respond to the additional initialize message. In the most recent definition, objects of the class Counter have two attributes number and reused, both with an initial value of 0 when created and two methods add and initialize. However, no instances of the class is crested, except by calling the object allocator function new. The expression new Counter returns a newly created instance of the Counter class.

However, in order that this new object may be referred to, it is assigned to an appropriate variable. Assuming the variable carpark in the fragment below, a new Counter object may be created via new Counter , and then assigned to the former: Counter carpark; Where more Counter objects are needed, the object allocator function new may be repeatedly invoked, and the resultant objects assigned to other vari- ables such as entrance and exitDoor: Counter entrance, exitDoor; Thus, the counts of the various Counters carpark , entrance and exitDoor are carpark.

number, entrance. number and exitDoor. number, respectively. The total number from these counters is: carpark. number Similarly, the initialize method of Counters carpark, entrance and exitDoor may be invoked via: carpark. initialize ; entrance. initialize ; exitDoor. initialize ; 3. As such, any changes in object representation propagates to dependent code, resulting in high software maintenance cost.

A common object-oriented programming practice is information hiding—to make object representations inaccessible to clients so that modifications in server object representations do not propagate excessively. This decoupling of dependen- cies reduces software maintenance cost. Limiting access to object representations in Java is mainly achieved by the two main constraint specifiers private and public.

The former limits access of the following entity to within the class construct, while the latter makes it accessible to any client code. In this case, accessor methods getNumber and getReused are required, as outlined in the following code fragment.

Representation inde- pendence is maintained by confining access to private attributes to within the class construct. This topic is further discussed in Chapter 8. An attribute x in a class does not necessarily have any se- mantic bearing with another as they have different scopes, and does not preclude using the same attribute there. This criterion requires a message with associated parameters to be uniquely matched with the intended method definition.

add would invoke the first method to increment by 1, while carpark. add 2 would invoke the new one just defined. The abstraction in object-oriented programming languages often allows these two opera- tions to be combined implicitly. As such, constructors may be seen as unique methods invoked implicitly when an object instance is created.

Implicit initialization relieves the programmer from performing this important function, but more impor- tantly prevents uninitialized objects as a result of absent-minded programmers. Care- fully designed constructors allow for object invariants to be maintained regardless of how they were created. Apart from having the same name as the class, and not having a return result type, a constructor is not different from a method.

It has similar syntax for its parameters and implementation body. In place of attribute initialization, our next Counter example uses a constructor method. This offers additional functionality compared with the former approach. As with methods, constructors may also be overloaded. This provides for varied ways for objects to be created and initialized.

As an object responds to messages by executing code in the method body to affect changes in its state, assignment is a very common operation. and are also operators. The last expression involves nested expressions: the result of p 5 is used in multiplication. When operands are mixed, the widest is used to prevent unexpected truncation. x y x y false false false false true true true false true true true true! returns true if the single operand is false. In addition to assigning the right-side value to the left-side variable, it also returns the value assigned.

As such, the assignment expression may appear in the context of an enclos- ing expression. In the example below, the result of the assignment operator to vari- able a is not used. This is because unlike the common arithmetic operators which associates from left-to- right, the assignment operator associates from right-to-left.

This is highlighted in the next section on operator precedence. In general, an assignment operator results in a side-effect since it changes the value of the variable being assigned. Since they are used in either postfix and prefix forms, four scenarios are as illustrated in the code fragments below. In the code fragments below, f is either incremented or decremented. For example, the expression A? B:C returns the value of B if A is true, else the value of C is returned.

g Typecast The typecast operator type E performs 2 basic functions at run-time depend- ing on the source expression E. For a numeric type such as int, float, or double , it converts the value to another of the specified type. For variable, the operator confirms that the object refer- enced is compatible with the specified class. Table 3. The operators at the top of the table have higher precedence than those at the bottom.

It is as though precedence pulls operands, so that operators with a higher precedence are evaluated before those with lower precedence. All binary operations are left-associative, except assignment operators which associate right-to-left. Table Operator precedence. Operator []. Associativity rules come into effect when equal precedence levels do not help in resolving evaluation order.

These statements are commonly grouped under condi- tional and iterative statements. a Conditional Statements Conditional statements allow for conditions to be attached to a statement as to whether it will be executed. The most basic form is the if statement. In the code fragment below, the statement S is executed only if the boolean condition E evalu- ates to true: if E S; A slight variation is the if-else statement which allows for an either-or choice.

If the boolean condition E evaluates to is true and S is executed, then R would not. The break statement causes flow-control to leave the switch statement immediately. In the case of the execution of statement S3 when E evaluates to c3, the absence of a break statement causes execution to continue to S4 instead.

The default limb is used when the evaluated value of E does not match any constant values in the limbs. b Iterative Statements Iterative statements allow for constituent statements to be executed repeatedly.

In the most basic way, the body of the while-statement below is repeatedly executed when the boolean condition E is true. The loop terminates when E is false, after which execution proceeds to the next statement: while E S; The while-statement is known as a pretest loop since the constituent S is only executed if the condition E evaluates to is true.

Thus, if E was false in the first instance, the statement S is never executed. On the other hand, the do-while statement is a posttest loop. R is first executed and subsequently while the boolean expression F evaluates to true, R is executed again. Again, the loop terminates when F evaluates to false. Thus, this control flow construct will execute R at least once.

It is considered the sequential construct as the group of statements it surrounds is treated as a single statement or processing unit. Thus, while the various control-flow constructs merely show a single statement as the constituent body, a block may be used where such constructs should contain more than one statement. In the code fragment below, the nested if-else statement allows for the number of even numbers and sum of odd numbers in the range to be computed.

As such, the scope of local variable declarations is the rest of the block in which the declaration occurs. This allows declarations and associated references to be localized, thereby aiding maintainability. With instance variables, a local declaration has the same form below, where T is the declared type of variable v.

The for-statement is often used as a counter-controlled loop to iterate through a loop a fixed number of times, even though it does not have explicit mechanisms for counter control. Its more generic function is to transfer control out of the innermost switch, while, do or for-statement. This is why using the break-statement ensures that only the statements associated with the case-limb are executed. In many situations, its use can result in a simpler program structure.

For example, the following two code fragments have similar effects. finished } T; } Finally, the continue-statement transfers control to the beginning of the inner- most iterative loop so as to reevaluate the boolean condition for the next iteration.

Unlike, the break-statement, control-flow does not exit from the loop. As such, the following two code fragments have similar effects. The size of an array need not be specified or computed during compilation. Instead, it is important to understand a Counter array as being similar with multiple variables, that is, it is an object that does not further contain Counter objects but merely references eight potential Counter objects. A method in a class definition has the fol- lowing general form, with the return-statement returning control-flow back to the message sender: T foo gT g, hT h If the sender does not require any results, the keyword void should be used as the return type.

In this case, the returning expression v would be omitted in the return statement. The return-statement need not be the last statement in the block as implied in the previous example. In a non-trivial structure, multiple return- statements might be used as in the next example, but the programmer must evaluate if the situation improves program structure and readability.

Generally, these constructs are representative of what Java offers. The class construct is key in Java because it allows for objects to be defined to model the prob- lem domain.

Below that, variables and methods are defined, which correspond to data and code. Code abstraction result in hierarchical statement blocks with optional local variables and control flow mechanisms. Figure illustrates this hierarchy. Java application consists of primitive values objects defined by class definitions consists of instance variables instance methods local variables statements assignment message control flow passing Figure Hierarchical relationships of Java constructs.

Which of the following are valid variable names in Java? Define a Square class with the length of its side as an instance vari- able. Include an appropriate constructor method and methods to enlarge an instance as well as compute its area. Using the Square class in Question 2, create ten randomly sized squares and find the sum of their areas. The method Math. random returns a random number between 0. Add the functionality for a Square object to draw itself via ASCII characters.

print and System. println methods may be useful. Note that each of the digits may be used once. For validation purposes, these concepts allow objects in our system to be operational. We now proceed to see how they are practically applied to example problems as typical programs. Enhancements involving mechanisms for the user interface may be subsequently considered. This is consistent with the software engineering principle of abstraction. Conceptually, the core calculator engine may be viewed as being comprised of registers to hold values, together with built-in operators such as addition and subtrac- tion to manipulate such values.

Having operations involving two operands, the calcu- lator needs at least two registers. Four arithmetic operations imply at least four operators. A compute operator is required to get its execution started, together with a clear operator to prepare the registers for new computations.

These correspond to the equal and clear keys on a calculator. Lastly, the digits form the basic input mechanism for numeric operands. We would assume that the display operator will retrieve a value for display on the calculator panel. Object initialization may be easily accomplished via constructor methods. In this case, a CalculatorEngine object is initialized via invoking the clear operator.

The resultant Java code skeleton for CalculatorEngine objects with this basic rep- resentation is shown in Listing Note that all operators easily correspond to instance methods, as well as to buttons on the face on a conventional calculator. Code represented by ellipses will be elaborated in due course. It is thus intuitive to set the variables value and keep to 0. The former is updated as a result of new inputs from numeric keys or the result of an operator, and thus is used to update the display area.

As expressions are keyed in using an infix notation e. The keep instance variable serves this purpose. int display { return value ; } 4. A new digit shifts existing digits in the value instance variable one place to the left.

This manipulation is accomplished by multiplication by 10 and followed by addition of the last digit. void one { digit 1 ; } void two { digit 2 ; } For this purpose, we define another instance variable toDo which records the action to be associated with the next compute operation. Subsequently, the code sequence c. digit 1 ; c. digit 3 ; c. add ; c. For verification purposes, the Java API Application Program Interface method System. println may be used to produce output on the screen: System.

println c. display ; There is, however, a slight snag: the CalculatorEngine object instance is the only object in existence, yet which object would send it messages to compute expressions? Or even more fundamental, at the very commencement of program execution when no objects existed, how was the first object created?

Java solves this issue through the introduction of class methods, which are invoked with respect to the class they are associated with rather than object instan- ces. More specifically, the body of the static method named main is the first code sequence to be executed. compute ; System.

display ; } The various code fragments may be brought together within a class construct in the file CalculatorEngine. java as shown in Listing display ; } } Listing CalculatorEngine class. java where CalculatorEngine.

Each evaluation of a new arithmetic expression requires editing code and recompilation. Ideally, we should be compiling the source once, but inputting different expressions for evaluation. It is common to have an user interface object to work cooperatively with the CalculatorEngine. We will initially consider a line-mode user inter- face and subsequently enhance it for a windowing environment. To this end, a CalculatorInterface object fulfills this role.

It has the role of a middleman that does not work too much, but instead accepts input and passes it onto the CalculatorEngine. Similarly, feedback from the CalculatorEngine is collected and becomes output for the CalculatorInterface object.

The implementation of CalculatorInterface consists of an initializing phase where a CalculatorEngine object is bound to an CalculatorInterface object, and an execution phase which performs the necessary dispatching.

These are imple- mented by the constructor and run methods of CalculatorInterface respec- tively, as illustrated in Listing import java. run ; } } Listing CalculatorInput class. Until these topics are discussed in Chapters 9 and 10, it is not harmful that at present, they be taken by faith.

It is useful for modular and secure programming methodology. It also suffices that the BufferedReader class facilitates input, and that the readLine method allows an input line to be read. java This provides the added flexibility of arbitrary computations via keyboard input sequences. To show the ease of code reusability when a neat modular structure is adopted, another user-interface framework to work with CalculatorEngine is introduced in this section.

Similar to CalculatorInput, CalculatorFrame provides an environment for a CalculatorEngine object to execute. Implementation in Java 47 Windowing facilities in Java will be discussed in Chapter However, this graphical calculator example is still appropriate since its objective is to show the benefits of modular code and reusable API libraries in Java. Code in the constructor method sets up a calculator frame with buttons and a display at appropriate locations.

Using a graphical user interface in this instance is fairly straightforward since mouse clicks on calculator buttons are mapped to actionPerformed method. As such, code that performs the necessary dispatching to CalculatorEngine shown in List- ing is similar to that in the run method in CalculatorInput. 原创 Js逆向教程浏览器调试工具-可视化的Elements 页面中有很多事件，比如说鼠标按下，滚动条滑动。最后的最后由本人水平所限，难免有错误以及不足之处， 屏幕前的靓仔靓女们 如有发现，恳请指出！你轻轻地点了个赞，那将在我的心里世界增添一颗明亮而耀眼的星！ 原创 python一招自动搞定Chromedriver爬虫驱动的更新 日常的web自动化过程中，我们常常用python selenium库来操纵Chrome浏览器实现网页的自动化。这其中有个比较头疼的问题：Chrome的更新频率非常频繁，与之对应的Chromedriver版本也必须相应更新。如果两者版本的主版本号相差超过1，selenium则会报异常.

那有没有好的办法解决这个问题呢？方法当然有，首先我们需要知道哪里可以下载到不同版本的文件。这里推荐两个网站，国内首选淘宝的镜像仓库：数据更新会比谷歌官方稍慢；可供下载的版本有时不全； 原创 如何安装MockingBird-AI拟声: 5秒内克隆您的声音并生成任意语音内容 作者：虚坏叔叔早餐店不会开到晚上，想吃的人早就来了！😄。 原创 Quasar — 免费开源的Windows远程管理工具 适用于Windows的免费开源远程控制管理工具Quasar是一种用C＃编码的快速轻量级远程管理工具。可用于管理工作到员工监控等。Quasar提供高稳定性和易用的用户界面，是您理想的远程控制管理解决方案。 原创 AutoJs4. 原创 将你的 Python 脚本转换为命令行程序 哈喽，大家好，今天给大家介绍一下，如何通过Python自动整理文件。 原创 如何通过Python自动整理文件？ 哈喽，大家好，今天给大家介绍一下，如何通过Python自动整理文件。 原创 如何用python自动化微信小程序 本文介绍了整个微信小程序的自动化过程。我已经将全部源码上传到后台上，关注文章底部公众号后回复「kja」即可获得。你的肯定是我最大的鼓励和支持。 2.

原创 如何在实体手机上，保证手机能够正常运行uiautomator2，并安装ATX-agent 如何在实体手机上，保证手机能够正常运行uiautomator2，并安装ATX-agent。以小米手机为例子，首先打开 设置-更多设置-开启开发者模式。如果初始化完成后，发现手机并没有安装ATXagent应用。说明设备未认证（unauthorized），此时，当你看到这个，就说明手机安装成功了环境。需要记得，将 USB安装 勾选上。 原创 address localhost is already in use（端口被占用）Windows系统问题解决 在学习编程的过程中，我们或许会遇到端口被占用的情况，因而导致程序启动不了。这种情况只需要找到占用端口的进程，然后在中关闭改进程即可解决问题。后面补加的图。 原创 mitmproxy的介绍以及配置过程中的问题 提示：以下是本篇文章正文内容，下面案例可供参考。 FinalShell 中文安装包 FinalShell 一款可以替代XShell 的ssh 客户端软件，不仅是 ssh 客户端软件，还是功能强大的开发及运维的工具。可以满足我们的工作需求 主要特性:.

net版本问题: 检查是否安装. reres chrome插件v1. app自动化课程的简介和介绍 app自动化课程的简介和介绍. windows 生成RSA公钥和私钥openssl. exe工具 1、打开 openssl. 多线程解决mfc对话框未响应、卡死问题 多线程解决mfc对话框未响应、卡死问题. 爆款少儿青少年scratch编程第4课：狮子钻火圈 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:. 爆款少儿青少年scratch编程第5课：熊熊吃什么 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:.

爆款少儿青少年scratch编程第18课：7的倍数（下） 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:. 爆款少儿青少年scratch编程第24课：阶段实战测试 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:. 爆款少儿青少年scratch编程第15课：寿司回家（上） 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:. 爆款少儿青少年scratch编程第11课：钓鱼大作战 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:.

爆款少儿青少年scratch编程第10课：暑期安全 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:. 爆款少儿青少年scratch编程第19课：BMI指数（上） 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:.

爆款少儿青少年scratch编程第13课：模拟时钟 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:. 爆款少儿青少年scratch编程第17课：认识祖国 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:. 爆款少儿青少年scratch编程第3课：猜猜我是谁 可以直接运行。A53课程制作 爆款爆款少儿青少年scratch编程是包括教程制作完整课程，里面包括教学步骤，教学视频，教学素材，教学课件pdf，教学课件word，课程源码。课程内容大致如下所示：资源:.

A footnote in Microsoft's submission opens in new tab to the UK's Competition and Markets Authority CMA has let slip the reason behind Call of Duty's absence from the Xbox Game Pass library: Sony and Activision Blizzard have a deal that restricts the games' presence on the service.

The footnote appears in a section detailing the potential benefits to consumers from Microsoft's point of view of the Activision Blizzard catalogue coming to Game Pass.

What existing contractual obligations are those? Why, ones like the "agreement between Activision Blizzard and Sony," that places "restrictions on the ability of Activision Blizzard to place COD titles on Game Pass for a number of years". It was apparently these kinds of agreements that Xbox's Phil Spencer had in mind opens in new tab when he spoke to Sony bosses in January and confirmed Microsoft's "intent to honor all existing agreements upon acquisition of Activision Blizzard".

Unfortunately, the footnote ends there, so there's not much in the way of detail about what these restrictions are or how long they'd remain in effect in a potential post-acquisition world. Given COD's continued non-appearance on Game Pass, you've got to imagine the restrictions are fairly significant if they're not an outright block on COD coming to the service.

Either way, the simple fact that Microsoft is apparently willing to maintain any restrictions on its own ability to put first-party games on Game Pass is rather remarkable, given that making Game Pass more appealing is one of the reasons for its acquisition spree. The irony of Sony making deals like this one while fretting about COD's future on PlayStation probably isn't lost on Microsoft's lawyers, which is no doubt part of why they brought it up to the CMA.

While it's absolutely reasonable to worry about a world in which more and more properties are concentrated in the hands of singular, giant megacorps, it does look a bit odd if you're complaining about losing access to games while stopping them from joining competing services.

edu no longer supports Internet Explorer. To browse Academia. edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. Mike S Jackson. Abenezer Yohannes. Vishwanatham Ramana. Isromi Janwar. Awais Manzoor. Aurika Taureci. badrus zaman. Sanchita Patil. adil king. Vâmsï Krïshñâ. Log in with Facebook Log in with Google. Remember me on this computer.

Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Object oriented Programming and java. XÐIEGO ORTEGA. Contract and Implementation Parts 79 6. Continue Reading Download Free PDF. Related Papers. Introductory Java Course. Download Free PDF View PDF. Comparative Studies of 10 Programming Languages within 10 Diverse Criteria -- a Team 7 COMPS10 Term Report.

JSP complete reference. web development. Oracle Certified Professional Java SE 7 Programmer Exams 1Z and 1Z Osborne Java 2 Complete Reference 5th Ed. Enquiries concerning reproduction outside those terms should be sent to the publishers.

The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. The focus of the next revolution was data abstraction, which proposed languages such as Modula and Ada.

As with many other programmers, good run-time checks with automatic memory manage- ment and a reusable API made Java a very attractive option. After a half-day on the original Java Whitepaper and the early Java online tutorial, we were sold on the Java bandwagon and already writing code. In situations where there is no large investment into older languages, we are quite happy to abandon them completely. Effective programming in Java comes from understanding three key areas — object-oriented concepts, the syntax and semantics of the Java programming language and the Java Application Programming Interface API.

This is our emphasis when we conduct professional courses, and in this book as well. Much of the material in this book is based on previous courses which we have conducted over the past two years to the industry and the National University of Singapore NUS. Courses conducted for the industry last about 5 to 7 days, depending on the amount of coaching that participants require. As you might have noticed, we have taken to Java as ducks to water.

Java has allowed us to think about and specify object behavior. This results in executable code which is merely secondary. What is important is the clean specification of object behavior. Similarly, in getting accustomed to working with objects, we believe that you will enjoy it too. Preface to 2nd Edition Since publishing the first edition almost 10 years ago, we have seen Java being used in many high school and university programming courses.

Further, many projects now use Java as the implementation language. Similarly, at the Institute of Systems Science, we have seen professional developers warming up to Java for the first time in , to those who use Java in their daily work in We have thus updated the material to cover J2EE topics such as JDBC, RMI, Serialization and Java Servlets.

We have also added a chapter on Generics as the Java language evolved to allow this elegant feature. For those who might be embarking on a Java journey now, we wish you a pleasant journey and a well-used road map. Many have taken this journey before and are enjoying the fruits of their learning investment.

Overview Chapter 1 presents an introduction to the object-oriented world consisting of objects and object communication via the exchange of messages. Object-oriented concepts and terminology used in object-oriented methodology are discussed in chapter 2. Chapter 3 shows how these concepts materialize in the form of Java code and representations.

It discusses the basic features and syntax of Java and builds upon the concepts using an incremental Counter example. Following on from language syntax, chapter 4 demonstrates the standard pro- gramming environment using the Java Development Kit JDK , and how a class definition may be compiled and executed, integrated and reused within other code fragments.

The chapter also delves into using the Java Application Programming Interface API to demonstrate the ease and productivity gains of code libraries. Chapter 5 returns to the discussion of objects, in particular, the organization of objects into manageable classes. The concept of class enables a developer to organize a complex problem domain into more manageable components. Grouping objects into classes is an act known as classification in object-oriented modeling.

When classes are formed, they can be further distinguished into superclasses or subclasses, accord- ing to their similarities or differences in properties. Class hierarchies can then be formed.

The creation of superclasses and subclasses is achieved through abstracttion mechanisms known as generalization and specialization respectively. Classification, generalization and specialization are thus important abstraction mechanisms for organizing objects and managing complexities.

Inheritance is discussed in chapter 6. Common properties of classes can be shared with other classes of objects via the inheritance mechanism. It is through inheritance that software component reuse is possible in object-oriented programming.

Software reusability is important because code need not be produced from scratch, thereby increasing the productivity of developers. Another topic close to the heart of object-oriented programming is polymorphism. This topic is concerned with object messaging and how objects of different classes respond to the same message.

With polymorphism, objects of different class definition can respond to the same message with the appropriate method. In this way, generic software code can be produced, thus enhancing the maintainability of software systems.

Polymorphism is supported by dynamic binding and operation overloading, topics that are central to the discussion in chapter 7. Enhancing software maintainability is a significant software development objective. A programming technique known as Structured Programming was intro- duced in the s, promoting modularity as a Software Engineering principle for achieving maintainable software.

Encapsulation is the manifestation of modularity in object-oriented programming to the fullest. As will be made clear in chapter 8, encapsulation brings together related properties into class definitions with the structural definition of classes hidden from their users.

The purpose of this approach is to hide the implementation detail of objects so that when changes in implementation of objects are called for, users of the objects will not be adversely affected. Exception Handling is considered in chapter 9. This is especially important in object-oriented programming, as the mechanism for the glue and safety net in code integration and reuse. Input and output rely on InputStream and OutputStream classes, as well as Reader and Writer classes in JDK 1.

Collection classes with Generics in chapter 12 show how the concepts of modu- larity and encapsulation work to facilitate code reuse. This chapter not only gives an overview of the classes in the Collections Framework, but this framework is an excellent sample of how reusable code is written.

The AWT model is elaborated with descriptions of its constituents and example usage for Graphical User Interfaces in chapter There are sufficient code examples to build interfaces for most simple applications. We have also incorporated Swing classes for better interactivity.

Applet development relate to graphical interfaces and the issue of dynamic loading of compiled Java bytecodes. This is discussed in chapter Situations where applet behavior differs from Java applications, security measures and implementing a loader over the network are also considered. Chapter 15 covers Java Servlets. It is related to dynamic code loading and applets in chapter 14, but occurring on the server side. This forms the basis for Java- based Web applications.

Chapter 16 examines Java Object Serialization and Remote Method Invocation. The former may be viewed as a continuation of input and output facilities discussed in chapter 10, but with the focus to implement object persistence. Object Serialization is also used to move objects over a network and forms a key role in implementing Remote Method Invocation RMI for distributed applications.

Instead Java supports single inheritance and provides a means by which the effects of multiple inheritance can be realized. For example, the following code fragment suggests that Employee is an exten- sion of the Person class; Manager, SalesPerson and Secretary, being subclasses, are extensions of the Employee class: class Employee extends Person { Important things you should know about Finite Trading Indicator: It never repaints. We champion the power of technology-centered financial services and advocate for the modernization of financial regulation to support inclusion and responsible innovation. Our U.

Categories:

• Forex
• Forex Bitcoin
• Binary Options online
• Binary Options
• Forex Brokers