備考攻略丨AP計(jì)算機(jī)A的用書(shū)建議和詳細(xì)考點(diǎn)梳理

點(diǎn)擊上方“藍(lán)色字”可訂閱哦！

在美國(guó)大學(xué)中學(xué)習(xí)，計(jì)算機(jī)知識(shí)是必不可少的，在以后的就業(yè)中，計(jì)算機(jī)應(yīng)用也非常廣，因此在選擇AP 科目時(shí)，很多中國(guó)留學(xué)生對(duì)計(jì)算機(jī)科目情有獨(dú)鐘。今天我們來(lái)梳理一下計(jì)算機(jī)A的考點(diǎn)，加油備考吧！

首先來(lái)看一下計(jì)算機(jī)學(xué)習(xí)和復(fù)習(xí)的用書(shū)建議。

輔導(dǎo)書(shū)類(lèi)：

Barron's AP Computer Science?A ★★★★★

巴郎的教材完全覆蓋AP考試考點(diǎn)，課后題目較多，難度、題型與考試相近，但知識(shí)點(diǎn)講解不夠深入，適合作為復(fù)習(xí)書(shū)和刷題使用。

Princeton AP Computer Science A ★★★★

題目難度偏低，適合初學(xué)時(shí)使用。和巴郎教材二選一即可。

Course Description ★★★★

不管準(zhǔn)備任何AP科目考試說(shuō)明都是最好的學(xué)習(xí)資料，適合前期明確考試范圍和后期查漏補(bǔ)缺時(shí)使用。

5?Steps?to?a?5 ★★★★

例題部分比 Barron 要少，難度相當(dāng)。

Think Java?How to Think Like a Computer Scientist ★★★

由于AP計(jì)算機(jī)考試中涉及的Java只是java的子集，所以本書(shū)只適合作為參考書(shū)使用。

下面是考點(diǎn)梳理，做好筆記哦！

1.Introductory Java Language Features

Package And Classes 類(lèi)和包

public class FirstProg // file name is FirstProg.java

{

public static type1 method1 (parameter list)

{

<code for method1>

}

public static type2 method2 (parameter list)

{

<code for method 2>

}

......

public static void main (String[] args)

{

<your code>

}

}

All java methods must be contained in a class; all program statement must be placed in a method

The class that contains the main method does not contain many additional methods.

reserved words (Keywords): class, public, static, void, main.

public: the class or method is usable outside of the class

static: methods that will not access any objects of a class. The main method must always be static.

Types And Identifiers 標(biāo)識(shí)符和類(lèi)型

Identifiers 標(biāo)識(shí)符

Identifier: name for a variable, parameter, constant, user-defined method, user-defined class

cannot begin with a digit

Lowercase: for variables and methods

Uppercase: separate into multiple words e.g getName, findSurfaceArea

a class name starts with a capitol letter

Built-in Types 內(nèi)置類(lèi)型

int - 整數(shù)

boolean - true or false

double - 小數(shù)

Storage of Numbers 數(shù)值儲(chǔ)存

Integers 整數(shù)

binary

Integer.MAX_VALUE == 2^31-1

Integer.MIN_VALUE == - 2^31

Floating-Point Numbers 浮點(diǎn)數(shù)

NaN"not a number" - undefined number

float & double

sign * mantissa * 2^exponent

round-off error - when floating-point numbers are converted into binary, most cannot be represented exactly

e.g 0.1*26 ≠ 0.1+0.1......(26 terms)

Hexadecimal Numbers 十六進(jìn)制數(shù)

conversion between hex and binary

5 hex = 0101 bin ? ? ? ? F hex = 1111 bin

5F hex = 01011111 bin

Final Variable ?Final變量

user-defined constant

keyword final

e.g. ? final double TAX_RATE = 0.08;

final variable can be declared without initializing it immediately, but can only be given just once

array bound

final int MAXSTUDENTS = 25;

int [] classList = new Int[MAXSTUDENTS];

Operators 運(yùn)算符

Arithmetic Operators 算數(shù)運(yùn)算符

+ addition ? - subtraction ? * multiplication ? /devision ? %mod(remainder)

Relational Operators 關(guān)系運(yùn)算符

== equal to ? != not equal to ? > greater than ? < less than ? >= greater or equal to ? <= less than or equal to

Relational Operators can only be used in comparison of primitive types.

User defined types : equals, compareTo ?methods

floating-point should not be compared directly using relational operators.

Logical Operators 邏輯運(yùn)算符

! NOT ? && AND ? || OR

Short-circuit evaluation

evaluated from left to right

evaluation automatically stops as soon as the value of the entire expression is known

Assignment Operators 賦值運(yùn)算符

Compound assignment operators :

= ? ? ?+= ? ? ?-= ? ? ?*= ? ? ?/= ? ? ?%=

Increment and Decrement Operator 遞增遞減運(yùn)算符

++ ? ? ?--

Operator Precedence 運(yùn)算符的優(yōu)先級(jí)

!, ++ , -- ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?right to left

* , / , % ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? left to right

+ , - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? left to right

<, >, <=, >= ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?left to right

== , !=? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??left to right

&&

||

=, +=, -+, *=, /=, %= ? ? ? ? ? ? ? ? ? ?right to left

Input/Output 輸入輸出

Escape sequences 轉(zhuǎn)義字符

newline

" ? ? ?double quot

backslash

Control?Structures 控制結(jié)構(gòu)

Decision-Making Control Structures 條件結(jié)構(gòu)

if...

if...else...

nested if

extended if (if...elseif...)

Iteration 循環(huán)結(jié)構(gòu)

for (initialization; termination condition; update statement)

The termination condition is tested at the top of the loop

the update statement is performed at the bottom

loop variable should not have its value changed inside the loop body

the scope of the loop variable can be restricted to the loop body by combining the loop variable declaration with the initialization.

for loop

for (SomeType element : collection)

cannot be used to replace or remove elements

hides the index variable that is used with array

for-each loop

 

while (boolean test)

while loop

2.Classes and Objects

Public, Private, Static 公開(kāi)，私有，靜態(tài)

public method

accessible to all client program

private method

can be accessed only by methods of that class

information hiding

all instance variables are private

Static variable (class variable)

keep track on statics for objects of the class

accumulate a total

provide a new identity number for each new object of the class

contains a value that is shared by all instances of the class

memory allocation happens once

usage

Methods 方法

Headers

Constructors

default constructor - no arguments

creates an object of the class

name: always the same as the class

has no return type

several constructors provides different ways of initializing an object

public BankAccount ()

{

myPassword = " ";

myBalance = 0.0;

}

BankAccount b = new BankAccount ();

the constructor with parameters

public BankAccount (String password, double balance)

{

myPassword = password;

myBalance = balance;

}

BankAccount c = new BankAccount (KevinC , 800.00);

Object b and c are object variables that store the addresses of their respective BankAccount objects.

Accessors 訪問(wèn)器

accesses a class object without altering the object.

returns some information about the object

getSomething()

Mutator ?存取器

changes the state of an object by modifying at least one of its instance variables.

setSomething()

Static Methods ?靜態(tài)方法

main() method

used to test other classes

all method must be static

class name . method name

object name . method name

instance methods : all methods operate on an?individual objects of a class (constructors, accessors, mutators)

static methods (class methods) : methods performs an operation for the entire class

Driver Class

Method Overloading ?方法重載

two or more methods in the same class having the same name but different parameter lists

signature : name & parameter types

return type is irrelevant

Scope 范圍

the region where the variable or method is visible and can be accessed

within the class all instance variable and methods can be simply accessed by name (not dot operator)

local variable : defined inside a method or statement. scope: the point where it is declared to the end of the block to its declaration occurs.

when a block is excited, the memory of a local variable is automatically recycled.

this Keyword

the instance method is always called for a particular object

implicit parameter - this

References 引用

primitive data types : double, int, boolean

reference data types : all objects

Difference : the way they are stored

primitive : each has its own memory slot

reference : contains the same address

aliasing : having two reference for the same object.

The Null Reference

a uninitialized object variable is called a null reference or null pointer

statement : object == null

object = null // set to null

NullPointerException - invoke an instance method with a null reference

if you fail to initialize a local variable in a method before you use it, you will get a compile time error

if you make the same mistake with an instance variable of a class, the code may run without error

if you don't initialize a reference instance variable in a class - NullPointerException

Method Parameters

formal parameter (dummy) : placeholders for actual parameter

actual parameter (argument) : supplied by a particular method in a client program

Passing Primitive types as parameters

When a memory is called, a new memory slot is allocated for each parameter.

Any changes made to parameters will not affect the values of the arguments in the calling program.

Passing Objects as parameters

the address is copied (not the value)

not possible for a method to make an object replace another one

can change the state of the object

3.Inheritance and polymorphism

Inheritance 繼承

Superclass and Subclass ?超類(lèi)和子類(lèi)

a subclass is bigger than a superclass - it contains more methods and data

Inheritance Hierarchy ?繼承層次結(jié)構(gòu)

a subclass can itself be a superclass of another class

subclass is-a superclass

is-a is transitive

method overriding - rewrite the method from superclass

partial overriding - part of the method is rewritten

Implementing subclasses ?實(shí)現(xiàn)子類(lèi)

keyword : extends

public class Superclass

{

// private instance variables

// other data members

// constructors

// public methods

// private methods

}

public class Subclass extends Superclass

{

// additional private instance variables

// additional data members

// constructors (not inherited!)

// additional public methods

// inherited public methods whose implementation is overridden

// additional private methods

}

Inheriting Instance Methods and Variables ?繼承實(shí)例方法和變量

the subclasses inherit all of the methods and variables of the superclass

instance variables are private and not directly accessible to the methods in the subclasses

classes on the same level in a hierarchy diagram do not inherit anything from each other

method overriding and the super keyword ?方法重載和super關(guān)鍵字

include a call to the superclass method

subclass method wants to do what the superclass does, plus something extra

a method in a superclass is overridden in a subclass by defining a method with the same return typer and signature

partial overriding

constructors and super ? 構(gòu)造函數(shù)和super

Constructors are never inherited!

the new instance variable must be explicitly initialized

if super is used in the implementation of a subclass constructor, it must be used in the first line of the constructor body.

if no constructor is provided in a subclass, the compiler provides the following default constructor

public SubClass()

{

Super();?? // calls default constructor of superclass

}

Rules for Subclasses

A subclass can add new private instance variables.

A subclass can add new public, private, or static methods.

A subclass can override inherited methods.

A subclass may not redefine a public method as private.

A subclass may not override static methods of the superclass.

A subclass should define its own constructors.

A subclass cannot directly access the private members of its superclass. It must use accessor or mutator methods.

Declaring Subclass Objects ?聲明子類(lèi)對(duì)象

Student s = new Student();

Student g = new GradStudent();

Student u = new UnderGrad();

A super class does not inherit from a subclass

Polymorphism 多態(tài)

Polymorphism is the mechanism of selecting the appropriate method of a particular object in a class hierarchy.

method calls are always determined by the type of the actual object, not the type of object reference.

the selection of the correct method occurs during the run of the program.

Dynamic Binding (Late Binding) 動(dòng)態(tài)綁定（后期綁定）

overloaded - selected at compile time - static binding, early binding

overridden - selected at runtime - late binding

compiler determine if a method can be called

run-time environment determine how it will be called.

Type Compatibility 類(lèi)型兼容性

Downcasting 向下轉(zhuǎn)換

downcast - casting a superclass to a subclass type

Student s = new GradStudent( );

GradStudent g = new GradStudent( );

int x = s.getID( ); // compile-time error

int y = g.getID( ); // legal

s is of type Student - Student class odes not have a getID method

can be fixed by casting s to the correct type

int x =?((GradStudent) s?).getID( );

the outer parentheses are necessary

The ClassCastException

a run-time exception thrown to signal an attempt to cast an object to a class of which it is not an instance

Abstract Class ?抽象類(lèi)

a superclass that represents an abstract concept

may contains abstract methods - have no implementation code, just a header

appears as a place holder

If a class contains any abstract methods, it must be declared an abstract class

The abstract Keyword ?abstract關(guān)鍵字

public abstract class AbstractClass

{ ... }

public class SubClass extends AbstractClass

{ ... }

if a subclass of an abstract class does not provide implementation code for all the abstract methods, it too becomes an abstract class

public abstract class Subclass extends AbstractClass

{ ... }

An abstract class can have both instance variables and concrete methods

the header is terminated with a semicolon

It is possible for an abstract class to have no abstract methods

An abstract class may or may not have constructors

No instances can be created for an abstract class

Polymorphism works with abstract classes as it does with concrete classes

Interfaces ?接口

Interface ?接口

a collection of related methods whose headers are provided without implementations

all methods are public and abstract (no need to explicitly include these keywords)

provide a framework of behavior for any class

Defining an interface ?定義接口

public interface FlyingObject {

void fly(); ?// method that simulate the flight of the object boolean isFlying(); ?// true if the object is in flight, false otherwise

}

The implements Keyword

public class Bird implements FlyingObject

public class mosquito extends Insect implements FlyingObject

The Comparable Interface

public interface Comparable

{

int compareTo (Object obj);

}

 

 

4.Some Standard Classes

The Object Class

The Universal Superclass

every class automatically extends Object

Methods in the Object

Object is NOT an abstract class

expectation : the methods will be overridden in any class where default implementation is not suitable

toString

public String toString()

when you attempt to print an object, the?inherited?default toString method is invokes

Array objects are unusual in that they do not have toString method

equals

public boolean equals(Object another)

return true if this object and other are the same object (referencing to the same memory slot)

equivalent to the == relation

 

The String Class

String Objects

a sequence of characters

immutable - no methods to change them after they've been constructed

constructing String Objects

can be initialized like a primitive type

String s = "abc"

String s = new String("abc");

it is possible to reassign a string reference

The Concatenation Operator

If one of the operands is a String and the other is a primitive type, then the non-String operand is converted to a String

If neither of the operands is a String object, an error occurs

Comparison of String Objects

overridden inherited from the Object class and overridden to do the correct thing:

equal

if (string1 .equals (string2)) ...

the String class implement Comparable

compares Strings in dictionary order

return true if string1 and string2 are identical strings

compareTo

java is case-sensitive

digits precede capital letters precede lowercase letters

Other String Methods

int length(

return the length of this String

String substring(int startIndex)

return a substring starts with the character at startIndex and extends to the end of the string

the first character is at index zero

StringIndexOutOfBoundsException if startIndex is negative or larger than the length of the string

String substring (int startIndex, int endIndex)

start at startIndex, end at endIndex-1

int indexOf(String str)

return the index of the first occurrence of str

return -1 if str is not the substring

if str is null -?NullPointerException

Wrapper Classes

The Integer Class

The Double Class

5.Program Design and Analysis

The Water Fall Model 瀑布模型

Analysis of Specification 程序詳細(xì)計(jì)劃書(shū)

a written?description?based on costumer's requirements

Program Design 程序設(shè)計(jì)

detailed overall plan without Java code

include all objects + data structure + list of tasks

Implementation 程序?qū)崿F(xiàn)

actual coding (具體接下來(lái)有)

Testing and Debugging 調(diào)試和測(cè)試

upgrading code as circumstances change

write a robust program to avoid bad input

compile-time error - occur during compilation e.g. syntax error

run-time error - occur during execution "throws an exception"

intent/ logic error - fails to carry out the specification of the program

typical values in each part of the domain

end point values

out-of-range values

Test Data 測(cè)試數(shù)據(jù)

Types of Errors (bugs) 錯(cuò)誤類(lèi)型

Robustness 穩(wěn)健性

Program Maintenance 程序維護(hù)

Object-Oriented Program Design 面對(duì)對(duì)象程序設(shè)計(jì)

Identifying Classes 確定類(lèi)

Basic Object

Collection

Controller

Display

Identifying Behaviors 確定行為

find all verbs in the program description

encapsulation 封裝 bundling a group of methods and data fields into a class

Think carefully about who should do what

Determining Relationships Between Classes 確定類(lèi)之間的關(guān)系

Inheritance Relationship 繼承關(guān)系 (is-a)

Composition Relationship 組合關(guān)系 (has-a)

UML Diagrams ?UML圖

實(shí)心箭頭 has-a

空心箭頭 is-a

interface 虛線

Implementing Classes 實(shí)現(xiàn)類(lèi)

start with an over view of the program

collaborators: all other classes needed for one particular class

independent: a class without collaborators

Independent classes are written and tested before being incorporated into the overall project

Bottom-Up development自下而上開(kāi)發(fā)

Top-Down development 自上而下開(kāi)發(fā)

Implementing Methods 實(shí)現(xiàn)方法

Procedure Abstraction 過(guò)程抽象

avoid repeating code

use helper methods

Information Hiding 信息隱藏

instance variable and helper methods are private

Stub Method 存根方法

stub - a dummy method

Algorithm 算法

Identifying Classes 確定類(lèi)

use nouns in the description

Relationship Between Classes 確定類(lèi)之間的關(guān)系

Identifying Behaviors 確定行為

Decisions 制定

Program Analysis 程序分析

Program Correctness 程序的正確性

Assertion 驗(yàn)證

Precondition 前提條件

postcondition 后置條件

Efficiency 性能

CPU time (number of machine operations required)

Memory (number and complexity of the?variables)

best case, worst case, average case

最后，提醒大家，考前記得多刷幾遍題哦！