java part1 www.underwar.co.il

8/3/2019 Java Part1 Www.underwar.co.Il

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JavaC++-

www.underwar.co.il.

, . , , ,

. , .

Nir AdarEmail: [email protected]

.


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1.

1. 2

2. 4

2.1. 4 2.2. J AVA VIRTUAL M ACHINE 5 2.3. 5 2.4. -C++-J AVA 6

3. -PACKAGES 7

3.1. PACKAGE 7 3.2. IMPORT 9 3.3. 9

4. JAVA 10

4.1. 10

4.2.

W RAPPERS 10

4.3. C ASE SENSITIVITY 11 4.4. -J AVA 11 4.5. 11 4.6. 12 4.7. 13 4.8. 14

4.8.1. 14 4.8.2. 14 4.8.3. DEFAULT CONSTRUCTOR 15 4.8.4. 15 4.8.5. 17

4.8.6. 18 4.8.7. 19 4.8.8. 20

4.9. 21 5.9.1. OBJECT 22 5.9.2. 22 5.9.3. -FINALIZATION 23 4.10. 24 4.11. FINAL 24

5. JAVADOC 25

5.1. 25


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5.2. 25 5.3. J AVADOC 26

5.4. -JAVADOC 28 5.5. -PACKAGES 31 5.6. J AVADOC 32


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2.

2.1.

Java ,-1995.

-C++.

JavaC++ .

JavaC++:

Java C++,unions.

-Java .

.

. -Java

)Exception(.

Java code verifier

.,Java ,

, .

.

Garbage Collector-Java ,

.Java -Garbage Collector,

.

-Java . -C++

. .

/, ,

, .


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2.2.Java Virtual Machine

Java -Java Virtual Machine)JVM.(

: Java, , ,

byte code. ,

native code.

-Java -Java

.

2.3.

Hello, World! .

Hello.Java

public class Hello{

public static void main(String[] args){

System.out.println("Hello, World!");}

}

:

-Java . . main. C++,

.

, .

) .(

Javac (Java Compiler) :

C:\>Javac Hello.Java


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3. -packages

3.1.package

-"" .

-Java packages.

-package,

:

package ;

.

:

// File MyClass.Java

package MyFirstPackage;

class MyClass{

}

,) ( -package

MyFirstPackage.

-package / -package

-default package.


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-class - package

-package.

, -package .

-package

-class -package.

-dJavac. ,

-package.

:

C:\> Javac -d C:\ MyClass.Java

-class

MyFirstPackage, C:\ .

packages.,package packages.

packages .

-package,

. -package

-packages -package -package.

-package , .


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3.2.import

,

. -import.

:

import ;

* packages.

package, , -package.

3.3.

package , import.

-packageJava.lang -Java,

.

package import, -package

-import.


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4. Java

4.1.

Java. C/C++

) ,

int,, 4 (,Java .

-Java unsigned -C/C++.

Type Size Minimum Maximum Literals Default* boolean - - - true, false Falsechar 16-bit Unicode 0 Unicode 162 1 'x' '\u0000'byte 8-bit 128 127 (byte)1 (byte)0short 16-bit 152 152 1 (short)1 (short)0int 32-bit 312 312 1 1, 0754,

0xfe0

long 64-bit 632 632 1 1L 0Lfloat 32-bit IEEE754 IEEE754 1.2f 0.0f double 64-bit IEEE754 IEEE754 1.2 0.0dvoid - - - - -

*- members variables.

4.2.Wrappers

,Java

, .

,Integer int:

Integer n = new Integer("4");int m = n.intValue();


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4.3.Case Sensitivity

Java Case Sensitive:main Main.

.

4.4. -Java

-Java :

, .

.

)final( .

,getPrice(), ,

.

4.5.

Java .

C++:

// blah blah

/* this is a blah blah */

, Java,Javadoc.

:

/** comment */


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4.6.

Java -C++.

,:

1. :,%(),+,*,/,-

2. = :,+=,=-,*=

3. :!=,==,=,>=> ,< ,<

4. ! :|| ,&& ,

5.++,--

Java-C -C,-Java casting

.

-C/C++ -Java:

sizeof -C /.

* .

& /.

:: .

, . -Java-

-for.


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4.7.

Java C++. :

if/else

if (expression){

// block}else{

// alternate block}

do/while

do{

// block}

while (expression);

for loop

for (initalize; condition; step){

// block}

switch... case

switch(indifier){

case VALUE1:case VALUE2:

// act 1 break;

default:// act2

break;}


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4.8.

Java . .

.

-Java ) ..(

4.8.1.

-Java C++:private, public, protected.

public, .

private, .

protected,

.

-Java , , -C++

. , package friendly.:

.

)package( , -package .

4.8.2.

, .

, .

. , .


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4.8.3.Default Constructor

-Java ,

. , , ,

-false -null.

, .

-C++,

.

4.8.4.

instantiation ,

, new.

instance )-reference ( . .

-Java . ,

, . )int, char'(

.

. ,

.:

Box myBox;

Box.


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reference

) reference

.(

C++:-C++ .

-Java . reference .

.

:

Box myBox = new Box();

reference null.

. ,

-reference. -Java.

Class-Type Class-Type.

, ,

.:

Car familyCar, sportCar ; familyCar = new Car();sportCar = familyCar ;

familyCar-sportCar reference.,

-familyCar -reference,

-sportCar -reference ,,reference.


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4.8.5.

== -Java .

,

, . .

:

Integer i1 = new Integer("3");Integer i2 = new Integer("3");Integer i3 = i2;

:

i1 == i1 && i1 != i2 && i2 == i3

.

boolean equals(Object o), :

i1.equals(i1) && i1.equals(i2)

.

-Java

Object. Object

equals. equals .

true .

== :, . , Java, , , ,,

.


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:

public class Name{

String firstName;String lastName;...

public boolean equals(Object o){

if (!(o instanceof Name)) return false; Name n = (Name)o;

return firstName.equals(n.firstName) &&lastName.equals(n.lastName);

}}

4.8.6.

-Java , .

.

length .

:

Animal[] arr; // nothing yet

arr = new Animal[4]; // only array of pointers

for(int i=0 ; i < arr.length ; i++)

arr[i] = new Animal();

// now we have a complete array

-Java .

-for .

-0 char ,-false

boolean. -null .


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-Java =, :

int vec1[] = {1,2,3};int vec2[] = {8,7,6,5};vec1 = vec2; // Won't copy the array!

, .

-Java,arraycopy.

arraycopy System:

public static void arraycopy(Object src,

int src_position,Object dst,int dst_position,int length);

:

int []vec1 = {1,2,3,4,5};int []vec2 = new int[vec1.length];System.arraycopy(vec1, 0, vec2, 0, vec1.length);

4.8.7.

-Java . ,:

String s = "Hello, World";

, -"Hello, World", s

.-Java , C/C++.

String .

, , -reference -String

String) .(


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4.8.8.

)class variables.(

,

.

static .

,

) . -C++, .(

.

, ,

.


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4.9.

,Java , .

Java:

class Base{

Base(){}Base(int i) {}

protected void foo() {}}

class Derived extends Base{

Derived() {} protected void foo() {}

Derived(int i){

super(i);super.foo();

}}

, :

class Base{

void foo(){

System.out.println(Base);}

}

class Derived extends Base

{ void foo(){

System.out.println(Derived);}

}

public class Test{

public static void main(String[] args){

Base b = new Derived(); b.foo(); // Derived.foo() will be activated

}}


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Java:-Java

C++. C++.

5.9.1.Object

Java, , Object.

,:

boolean equals(Object o);Object clone();int hashCode();String toString();

.

5.9.2.

, .

.

.

C++.

:

public abstract class Shape{

public abstract void draw();

public void move(int x, int y){

setColor(BackGroundColor);draw();setCenter(x,y);setColor(ForeGroundColor);


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draw();}

}

public class Circle extends Shape

{ public void draw(){

// draw the circle ...}

}

5.9.3. -Finalization

Objectfinalize().

. ,

. :

, '. -Destructor

C++, -Garbage Collector

, -C++ ,

-Java.

finalize :

1. finalize().

2. .

3. void.

4. protected.

finalize()

Object.


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4.10.

" " .

, :

)public(

-public, static-final.

, .:

interface IChef{

void cook(Food);}

interface Singer{

void sing(Song);}

interface SouthParkCharacter{

void curse();}

class Chef implements IChef, SouthParkCharacter{

public void curse() { } public void cook(Food f) { }

}

4.11.final

final , .

-final .

-final .

-final . .


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5.Javadoc

5.1.

.Java

. Javadoc.-Javadoc

-Java HTML "

.

5.2.

Javadoc/** -*/.

Javadoc : -Javadoc.

Javadoc ) ( .*

:

/*** This is the descriptive text of the doc comment.** @Xxx Comment for the tag.* @Yyy Comment for the tag.

*/ public class Aaa

{}

- javadoc // '...

.


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, **/ :- /* .

- javadoc *.

HTML . -HTML .

"

.

Javadoc

. .

. -summary, .

5.3. Javadoc

-Javadoc .

:

,

-Javadoc

:Overrides ) .(

, -interface

-Javadoc :Specified by ) -interface.(

", -Javadoc

)

-interface.( , -interface

.


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- javadoc) ,packages, interfaces,,,

( >code


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5.4. -javadoc

- javadoc, ,

- javadoc. @ .

javadoc

.,, @author

, . , - javadoc

.

- javadoc :

javadoc field:

javadoc -field :@see,@since-

@deprecated.

javadoc class

interface:

@author author name

-class/interface.

@author javadoc.

@see className

class,interface,methodfield.

:

fieldmethod) ( : @see # nameOfMethodOrField

fieldmethod) ( :

@see nameOfOtherClass#nameOfMethodOrField

method (overriding methods)

/

/ .

@see java.awt.Container#add(String,Component) javadocclass\interface @see.


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@since sinceText

-field\method\constructor\classinterface

JDK.

@deprecated deprecatedText

-class -interface -deprecated)(,

. /

. -deprecated

"No replacement".

Javadoc -method

constructor:

@param parameterNameDescription

-method -constructor.:@param size long size of

the file. @param .

, -a,anthe.:

@param num the int number to be tested. )

.(- javadoc -CODE

) @param.(

, /

. , .

@return description

-method.:@return length of the file

void-construcotrs .

@exception fulltQualifidClassNameDescription

-exception . Throws: -HTML -exception

. exception - javadoc ) -

exception.(:@exception IOException if the file is too big

@throws @exception. exception -throws

exception )errors-

NullPointerException.(


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@see className

, , See Also.

) .(

@since sinceText

.@since -class/interface.

@since -class/interface

class/interface.

@deprecated deprecatedText

method\constructor (deprecate).

deprecated .

deprecated.

@link .

-deprecated No replacement.

{@link}

.

Applet:

/*** Returns an absolute URL naming the directory of the document

in which* the applet is embedded. For example, suppose an applet is

contained* within the document:* * http://java.sun.com/products/jdk/1.2/index.html* * The document base is:* * http://java.sun.com/products/jdk/1.2/* ** @return the {@link java.net.URL} of the document that

contains this* applet.* @see java.applet.Applet#getCodeBase()*/

public URL getDocumentBase() {return stub.getDocumentBase();

}


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-Default Constructor:

default constructor

.

5.5. -packages

-packages package.html,

(*.java). -package

package.html package.

package.html package

-interfaces. -interfaces

package.html) -BODY.( package.html

package, -

interfacesc API

documentation.

HTML.

/**-*/ .

package.html:

:

Package Xxx Description. -

package.,Provides classes and interfaces for handling mobile

communication".. . : -package specification: .

: Related Documentation: ), '.(

@category :

-classes-interfaces -package. , -

packages,classes-interfaces.


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5.6.Javadoc

-Javadoc :

javadoc [options] [package | source.java]

, Javadoc )(-package

)-packages(HTML. -HTML

publicprotected.

package., -Javadoc HTML

)tree.html( HTML index

.

-options / / ) /

-package\packages(:

-public

-HTML public

.

-protected

-HTML public

protected.

-package

-HTML public,

protectedpackage friendly.

-private

-HTML .


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-author

-HTML @author .

-HTML.

-d directory

-HTML .

-sourcepath path

-path -package

-packages) -Javadoc

( -path -source code

javadoc.

javadoc -package)-package

.(

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