Java编程入门指南：期末复习Cheat sheet

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Java编程入门级复习指南是针对加拿大计算机专业Level 1学生的一份重要参考资料，课程名称为CST8116《计算机程序设计基础》。这份Cheat sheet旨在帮助学生系统复习Java编程的基础知识，以便准备期末考试。复习内容主要包括以下几个关键知识点： 1. **开发流程**： - **Joyce Farell开发循环**：该方法强调理解问题（Step 1）、规划逻辑（Step 2）、编写代码（Step 3）、将代码转化为可执行形式（Step 4，通常指编译），然后测试程序（Step 7），将程序投入生产环境（Step 8），并维护程序（Step 9）。 - **Cay Horstmann开发过程**：同样注重理解问题（Step 1），但更侧重于制定算法（Step 2）、用简单输入测试算法（Step 3）、将算法转化为代码（Step 4）、编译和测试程序（Step 5）。 2. **算法与伪代码**： - 算法定义为解决问题的步骤序列，始于一个起点，终至一个终点。计算机程序本质上就是算法的实现，每个步骤被称为一条语句。 - 伪代码和流程图是设计算法的有效工具，它们帮助开发者可视化和规划程序的逻辑结构。 3. **面向过程（ Imperative）与面向对象（Object-Oriented，OO）编程**： - Imperative编程（如Java）关注指令的执行细节，要求程序员明确描述如何处理数据以达到预期结果。 - 面向对象编程（如Java）则更加抽象，通过声明类和对象来请求软件提供结果，软件会自行决定如何实现。 4. **UML（统一建模语言）**： - UML类图是面向对象编程中的蓝图，用于表示对象及其之间的关系，帮助程序员组织和设计复杂的程序结构。 5. **API文档与模块与包**： - 模块是组织代码的一种方式，通过划分成可重用的部分提高代码管理效率。而包则是组织类的一种结构，有助于避免命名冲突。 - 在Java中，API文档对于模块和包的详细说明至关重要，它提供了函数、类和接口的使用指导。这些知识点涵盖了从问题理解到实际编码，再到软件结构和文档编写的关键环节，是Java编程学习和复习的核心要素。考生在准备考试时，应当熟练掌握这些概念，并能够运用到实际编程实践中。

Joyce Farell development cycle: 1) Understand the problem; 2) Plan the logic; 3) Write the code; 4) Translate the code; 7) Test the program; 8) Put the program into production; 7)

Maintain the program.

Cay Horstmann development process: 1) Understand the problem; 2) Develop and describe an algorithm; 3) Test

algorithm with simple inputs; 4) Translate algorithm; 5) Compile and test the program.

Algorithm: A solution to a problem, as a sequence of steps initiated with one starting point, and finishing at one exit

point. Computer programs are algorithms, and each step is referred to as a statement.

Pseudocode and Flowcharts: Use to plan an algorithm. UML class diagrams: blueprints for objects which are used by

programmers who are using an OOP language.

Imperative programmers: OPP and PP are imperative because they are required to detail how the program will

process data to get to the result. Declarative programmers: SQL is declarative because it requests the software to

provide a result and the software determines how to get the result.

API documentation (Modules and Packages): Modules are ways to organize packages, and packages are a way to organize classes. Java. Lang

(imported automatically) classes are used in all Java programs like String. Java. Util (imported explicitly) classes that provide miscellaneous

utilities like Scanner.

Methods: a way to break large sequences of processing steps, into smaller, re-usable units (functional decomposition). Unlike variables, which are

a named place (named as a thing [noun]) in the computer’s memory that stores a value, a method is a named place (named as an action [verb]) in

the computer’s memory that contains processing steps. Calling methods can be documented like an external method call. Method overloading:

occurs when two methods have the same name, but different signatures (type and the number of parameters). The compiler uses the parameters

to determine which method to use. Work methods: Methods inside a class that perform calculations or provide a service. Modularization: allows

abstraction (a method name represents processing, making it easier to program at a higher level), the ability of multiple programmers to work on different parts of a program at the

same time, and code reuse. Its only drawback is overhead: modules use more resources (memory, processing) than just coding steps.

Parameters: The data types and variable names are defined as part of the method definition (where data can be provided to the method). Arguments: Data passed to a parameter

within the parameters list.

Class: a class is a blueprint for an Object. We use a class to construct objects in the computer’s memory. Object: An object is an allocation of memory that contains properties (data

stored in attributes) and behaviors (methods that perform processing on the data inside the object). Through objects, we can break a problem’s solution into many smaller parts.

The public methods of a class are collectively referred to as its public interface. Constructors: a method used to instantiate an object based on the class definition. They require the

“new” operator to work. The “new” operator does not return the object, it returns a reference to the object in memory. Typically, constructors are overloaded. The public methods

of a class are collectively referred to as the public interface of the class.

Accessors: A method that returns a value held in an object and that does not change the state of the object. Mutator: A method that does not return a value but modifies the state

of the object.

Variables: [modifiers][data type][identifier][assignment operator(=)][initial value]. A variable identifier must start with a letter or underscore character. Special characters or the

$ symbol are not allowed. The assignment operator is right-associative. Before we can use a variable, we must initialize it. This can be done on the same line or on different lines.

Constant: A constant is a variable that has been constrained so that once a value is set, it cannot be changed. Constants in Java are declared by adding the keyword ‘final’ in front of

the data type.

Static class: Static members belong to a class and they are used at the class level, not at the object level. The keyword static is used

to indicate that a variable is part of the class. Utility methods that do not use any of the instance variables can also be labeled as

static (like the main method). Statics variables are allocated into memory once and each object instantiated from the class shares a

copy of the static member in memory. The Java Virtual Machine performs a lot of work when we use a static class member. We can

use a static member in an instance member, but we cannot use an instance member inside a static member.

Reference types VS primitive types: A Primitive type stores the value directly in the memory the variable represents. Primitive

types are stored in separate memory locations, independent of each other. Reference type stores a reference-to-an-object in

memory, but it does not store the object itself. The memory location assigned to a reference type doesn’t store its actual value, it

stores a reference to the position (address) in memory where the value of the object is located.

Scanner: private Scanner scanner = new Scanner (System.in); next() will read in text

data until it encounters any whitespace character, then it will return the next data up to

the whitespace. nextLine() will read in all the data until it encounters a line terminator

character (enter key). Use nextLine () when asking a user to enter the full name on one

line. nextLine () is not good when asking a user to enter numbers and text one after the

other. nextInt () and nextDouble ()stop, when they encounter an enter key character in

the input but don’t remove it. nextLine () reads in data and exits immediately when it

sees \n, if nextInt() or nextDouble() were used first, nextLine see’s the removes the

, and returns an empty String. The result is the program skips an entry and the user cannot type anything in. The fix is to call nextLine () immediately after any call to nextInt() or

nextDouble().

Unified Modeling Language: a UML Class diagram is a type of UML diagram that represents a design for a class and is not language specific. They can also include the data types

and go after each identifier: .

Instance variables: are declared at the class level, and exist in memory while the instance exists in memory.

Access modifiers: We cannot use the access modifiers inside a method, local scope variables, including parameters are implicitly private to that method.

This keyword: When the program is running, ‘this’ is made to reference an object from the inside. There are two uses for this: 1) To call another constructor internally. 2) To resolve

the scope, between instance variables at the class level, and local-scope variables at the method level that have the same name. Scope: The visibility of a variable, depends on

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