rocking on java

8/3/2019 Rocking on Java

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Rocking on JavaVo Minh Tam

[email protected]


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Intro

Objective Understand OOP

Review all features of Java language Get you out of confusion

U date latest chan es in Java since 1.5

pg. 2

How to make your code more beautiful

Requirement

Understand OOP Have a little knowledge with Java


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Outline

Java Basics

Java Advanced

Code Convention

Performance Tips

pg. 3

es gn a ern


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Java Basics


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Outline

Java Basics A little history

Features OOP

Exception Handling

pg. 5

Thread

GUI & IO & Networking & Database

Java Advanced

Code Convention

Performance Tips

Design Pattern


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A little history

1991

James Gosling

Oak Java

Star 7: a personal hand-held remote

pg. 6

con ro Includes

J2EE

J2SE

J2ME


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Features

JVM Bytecode

Garbage Collection

Code Security

pg. 7

ass oa er Bytecode verifier


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Java Basics

Class and Object

Abstract class and interface

Encapsulation

Inheritance

OOP

pg. 8

Polymorphism Overload

characterized by their properties and behaviors


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Java Basics

Abstract class and interface Same

Derived class must implement all abstract methods

Cannot create instances by using new operators

The purpose in POLYMORPHISM

Difference from abstract class

OOP

pg. 9

[I] Have multiple interface in one class [I] CANNOT include nonabstract method

[I] Interface is NOT designed to be superclass. Interface isdesigned to add some behaviors to a class.

A relationship between class/abstract class and class is astrong relationship. It is known as IS-A relationship.

A relationship between class and interface is a weakrelationship. It is known as Is-kind-of relationship.


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Java Basics

Inheritance Super and sub class

Object members Constructor Calling Chain

Override

OOP

pg. 10

instance methods

static methods hiding methods

Casting

Final class and method


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Java Basics

PolymorphismOOP

pg. 11

Ph.D Nguyen Hua Phung, Dept of CSE


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Unified Modeling Language (UML) class diagram

10..*

abstractstatic

association

(using)

privateinheritance

(is a)


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Java Basics

Error vs. Exception Immediate subclasses of Throwable

Error

Exception

(1) Generally beyond the control of user programs Out of memory errors

Exception Handling

pg. 13

ar s cras

(2) Usually the result of some flaws in the user programcode

Checked Exception vs. Unchecked

Exception


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Java Basics

Error vs. Exception

Checked Exception vs. Unchecked

Exception Common unchecked exception

NullPointerException

Exception Handling

pg. 14

ArithmetrictException IllegalArgumentException

IllegalStateException

UnsupportedOperationException

AssertionError


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Java Basics

Exception Handling

pg. 15


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Java Basics

Collection

pg. 16


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Java Basics

Normal Array vs. List

Vector vs. ArrayList

Traversing

Collection

pg. 17


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Java Advanced


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Outline

Java Basics

Java Advanced

Scanner printf

pg. 19

Enumerated Types

Foreach loop

Generic Types

Code Convention

Performance Tips

Design Pattern

Java 1 0 Java 1 1 Java 1 2 Java 1 3 Java 1 4 Java 1 5


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java.nio, javax.imageio,javax.net, javax.print,

javax.security, org.w3c

javax.activity,javax.

management

Java 1.08 packages

212 classes

Java 1.123 packages

504 classes

Java 1.259 packages

1520 classes

Java 1.377 packages

1595 classes

Java 1.4103 packages

2175 classes

Java 1.5131 packages

2656 classes

New Events

Inner class

Object

SerializationJar Files

International

JFC/Swing

Drag and

Drop

Java2DCORBA

JNDI

Java Sound

Timer

Regular ExpLogging

Assertions

NIO

java.applet, java.awt, java.io, java.lang, java.net, java.util

java.math, java.rmi, java.security, java.sql, java.text, java.beans

javax.accessibility, javax.swing, org.omg

avax.naming, javax.sound,javax.transactionReflectionJDBC

RMI


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Other New Features

Static import: import static java.Math.*;

Variable length argument lists.

pg. 21

Semaphores

Metadata


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java.util.Scanner

Initialize Scanner stdin = Scanner.create(System.in);

Scanner stdin = new Scanner();

Read from keyboard

pg. 22

hasNextXXX()

InputTest.java


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printf method

Similar to C style printf

Handles

strings

native types

pg. 23

java.util.Date

See java.util.Formatter for details

OutputTest.java


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Autoboxing/Unboxing

Wrap ints into Integers

Extract ints from Integers Automatically

Notice

pg. 24

NullPointerException with wrapper class Inmutability

This is now legal:Integer x = 6; //6 is boxed

Integer y = 2*x + 3; //x is unboxed, 15 is boxed

AutoBoxTest.java


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Object Only Performance

int x = 6;

int y = 2*x;

Code:

0: bipush 6

pg. 25

: s ore_

3: iconst_2

4: iload_1

5: imul

6: istore_2


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Integer x = 6;Integer y = 2*x;

Code:

0: bipush 6

2: invokestatic #2;

//Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;

pg. 26

5: astore_1

6: iconst_2

7: aload_1

8: invokevirtual #3;

//Method java/lang/Integer.intValue:()I

11: imul

12: invokestatic #2;

//Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;

15: astore_2


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Integer x = Integer.valueOf(6);

Integer y = Integer.valueOf(2 * x.IntValue);

pg. 27

Generates the same byte code.

EnumTest.java & EnumAdvanceTest.java


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Type-safe enum

enum Day { SUNDAY, MONDAY, TUESDAY,WEDNESDAY, THURSDAY,FRIDAY, SATURDAY }

//usedDay today = Day.WEDNESDAY;

pg. 28

switch(today){case SUNDAY:

break;

//}



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More Complex Enum

enum Suit {CLUBS(Color.BLACK),DIAMONDS(Color.RED),

HEARTS(Color.RED),SPADES(Color.BLACK);

pg. 29

private Color color;

Suit(Color color) { this.color = color; }

public Color getColor() { return color; }}



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Generics

ArrayList list = newArrayList();

list.add(new Integer(5));list.add(6);

pg. 30

s .a new ou e . ;list.add(new

BigInteger("123456789012301234567890"));

list.add(new Long(127L));

Number n = list.get(i);GenericUseTest.java


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Defining Generics

public class GenericStack implements Iterable{

private T[] data;

public GenericStack() {

data = (T[])new Object[MIN_SIZE];

pg. 31

public T pop(){ }

public void push(T item) { }

public Iterator iterator(){ } //since it is iterable

}


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Defining Generic Iterator

//inner class of GenericStack

private class GenericStackIterator implements Iterator {

int index;

GenericStackTestIterator() {

index = top;}

public boolean hasNext() { return index >= 0; }

pg. 32

public T next() {

if(index < 0) {

throw new java.util.NoSuchElementException();

}

T item = data[index];

index--;return item;

}

public void remove() {

throw new UnsupportedOperationException( )

}

( )


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For each loop (arrays)

double[] array = {2.5, 5.2, 7.9, 4.3, 2.0};

for(double d: array){

S stem.out. rintln d

pg. 33

}

Iterate (forward) through the array withoutpaying attention to indices.

ForLoopTest.java

F h l (C ll ti )


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For each loop (Collections)

ArrayList list = newArrayList();

list.add(7);list.add(15);

pg. 34

s .a - 7 ;for(Integer number: list){

System.out.println(number);

}

F h l


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For each loop enums

for( Suit s: Suit.values()){

System.out.println(s.getColor());

}

pg. 35

values() returns an Iterator for enum types


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Code Convention

O tli


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Outline

Java Basics

Java Advanced

Code Convention Class, Variable, Method

pg. 37

Comment Naming

Performance Tips

Design Pattern

P i St l G id li


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Programming Style Guidelines

80% of the lifetime cost of a piece ofsoftware goes to maintenance.

Hardly any software is maintained for itswhole life by the original author.

pg. 38

readability of the software, allowingprogrammers to understand new codemore quickly and thoroughly.

If you ship your source code as aproduct, you need to make sure it is aswell packaged and clean as any other

product you create.



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pg. 39

http://www.3cardbragrules.com/solutions/index-quality.html

Code Convention


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Code Convention

Well-organized in package

Classes should be declared inindividual files with the file name

matching the class name Avoid God classes -> remember

Single Responsibility Principle

ClassMicroarrayData

layout: Layout

R: double[][]

G: double[][]

Rb: double[][]Gb: double[][]

nbrOfSlides(): int

nbrOfSpots(): int

swa D es ...

Class name

Fields

pg. 40

e s Class (static) variables

Instance variables public class variables

protected

package level (no access modifier)

private

Methods These methods should be grouped by

functionality rather than by scope or

accessibility

append()

as.data.frame(): data.framegetLayout(): Layout

setLayout(layout)

subtractBackground(...)

normalizeWithinSlide(...)

normalizeAcrossSlides(...)plot(...)

plotSpatial(...)

boxplot(...)

hist(...)

static read(...): MicroarrayData

write(...)

Methods

Code Convention


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Code Convention

Minimize the scope

the visibility

the mutability

One variable per declaration

Variable

pg. 41

Use generics-version of a type instead of its rawtype when possible

Code Convention


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Code Convention

only one job

Avoid methods which have more than 30 lines of code

Public methods must validate their input arguments

Avoid writing methods accepting any more than 5parameters -> wrap them

DRY (Dont Repeat Yourself)

Methods

pg. 42

Return empty collection instead of null

Code Convention


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Code Convention

Do not use status code to communicate error conditions

Never declare an empty catch block

Only use the finally block to release resources from a try

statement Catch with specific exception first

Catch as lately as possible

Exception Handling

pg. 43

Code Convention


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Code Convention

Single line comment

// TODO, // HACK

Block comment

Special Javadoc comment

/***/

Comments

pg. 44

Popular tags @author

@version

@param

@return

@throws @see

@since

@deprecated

Advices

Remove unused code

http://javaworkshop.sourceforge.net/chapter4.html

Code Convention


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Code Convention

Naming rules:

Must consist of only letters, digits, _ and $

Cannot start with a number

Cannot use Java reserved words

Naming Conventions:

Naming

pg. 45

Class names are capitalized with each new wordcapitalized

Variable names have lower case letter, new words areseparated by _ or start with a capital letter (except for the

first) Methods starts with verbs in camel case

E.g.: getLayout(), normalize(method, slides)

Constants are all in upper case

Code Convention


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Code Convention

Naming advices

Names should be short but meaningful e.g. nbrOfGrids (orngrids) is much better than ngr

Use nouns for names of interfaces, enums,delegates, classes and variables.

Naming

pg. 46

o use en ers suc as r ng, ys em, ou , e care not reserved words and could be used

Use as English rules

Consider prefix Boolean variables and propertieswith can, is or has

Code Convention


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Code Convention

good programming style means that your programis readable

Style

pg. 47

Code Convention


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Code Convention

good programming style means that your programis readable

Blank lines between Instructions Functional block

Writin multi le instructions on one line

Style

pg. 48

Separating an instruction onto multiple lines Adding spaces between words

Declare array type

Use one and only one statement per line.

Code Convention


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Code Convention

Block section Indent with tab character (4 characters)

if else, while, do, try catch Do not nest code any more than 3 levels of

depth

Indentation

pg. 49

Line Not excess 80 characters each line

70 characters for documentation

Wrapping Lines Break after a comma.

Break before an operator.

Code Convention


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Code Convention

One declaration per line is recommended sinceit encourages commenting

initialize local variables where theyre declared

Placement

Declarations

pg. 50

Code Convention


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Code Convention

String StringBuilder > StringBuffer > String concatenation

enum

Use enum types instead of constants when possible for: Use foreach-style loop instead of for

Other

pg. 51

switch: include default case

Do not use magic number

Do not miss access modifier Avoid boxing and unboxing value types

Use prefix in UI components


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Performance Ti s

Performance Tips


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p

pg. 53

Performance Tips


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p

Prefer static final

Perfer static method

Avoid getter and setter

Use exact type when creating new object ArrayList a = new ArrayList() > List


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p

Avoid use Collection, use native array

Avoid Enums Where You Only Need Ints public enum Shrubbery { GROUND, CRAWLING, HANGING }

Use public static final int instead

Use Floating-Point Carefully Use double instead of float

pg. 55

Know And Use The Libraries Use System.arraycopy, String.indexOf

Questions?


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pg. 56

References


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J2SE Sang Shin course

Code Convention Document from SUNMicrosystems

KMS Code Convention Buu Nguyen, Duy Lam

http://www.jpct.net/wiki/index.php/Performance

pg. 57

_ ps_ or_ n ro

http://d.android.com/guide/practices/design/performance.html

Calvin Austin. J2SE 1.5 in a Nutshell.

http://java.sun.com/developer/technicalArticles/releases/j2se15

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