From Java to C/C++

Mechanism

Exception Handling

Memory managemen

t

OOP

Function

PointerData structure

Variable & constant

Storage class

specifiers

Data type

Package

OUTLINE

Java vs. C/C++

AlgorithmsLogic

Coding skill

High levelOOP only

Byte-code

JVM

Well supported build-in library

Pointer

Manual memory management

No well supported build-in library

Cross platform

Support UI lib

No standard UI lib

Both OOP & non-OOP

GC

Applet

Midlet

main()

main()C/C++

Filename same as classname

Hello world

C/C++

class HelloWorld{ public static void main(String args[]) { System.out.println("Hello World!"); }}

#include "stdio.h"void main(){ printf("Hello World");}

HelloWorld.java

Anyname.cpp

C/C++ compiler

Building

Java compiler

Achieve

.jar

.java

.class

Byte code

javac.exe Prep. source

.o

Linker

Executable

preprocessor

gcc / g++cl

gcce/arm

.h.cpp/.c

Use cpp.exe for preprocessing if

need

Processor

Running

JVM

OS

C/C++ executable

Java executable

java.exe

Package

Mechanism

Exception Handling

Memory managemen

t

OOP

FunctionPointer

Data structure

Variable & constant

Storage class

specifiers

Data type

OUTLINE

Package

C/C++

packageimport

namespace

using namespace

package illustration;import java.awt.*;public class Drawing { . . .}

using namespace std;namespace demo{

class DemoClass{

…};

}

Use: ‘ :: ’<namespace>::<subnamepace>::…::< subnamepace >::<class>::< static properties/functions>MyNamespace::MyClass::MyStaticFunction()

<namespace>::<subnamepace>::…::< subnamepace >::<var/function>std::cin

Use: ‘ . ‘ or ‘ -> ’ for accessing class’ properties, fucntionsMyNamespace::MyClass *cA = new MyNamespace::MyClass ()cA->Foo1();(*cA).Foo2();

Scope resolutionUse: ‘ . ’<package>.<subpackage>…<subpackage>.<class>.<properties/functions>

java.lang.Math.abs(a)

C/C++. or -> when & why

Use import for shorten call:import java.lang.Math;Math.abs(a);

Use using namespace for shorten call:using namespace std;cin >>a;

Data type

Package

Mechanism

Exception Handling

Memory managemen

t

OOPFunction

Pointer

Data structure

Variable & constant

Storage class

specifiers

OUTLINE

Primitive Data TypesJava C/C++ (32 bits) Range

void void n/a

char unsigned short / unsigned char 2 bytes / 1 byte

byte char / signed char 1 byte-128 … 127

short short / short intsigned shortsigned short int

2 bytes-215 … (215 – 1)

int int / signed intlong / long int / signed long / signed long int

4 bytes-231 … (231 – 1)

long long long / signed long long 8 bytes-263 … (263 – 1)

boolean bool 1 byteTrue/false

float / double float / double 4 bytes/ 8 bytes

Primitive Data Types• NO “unsigned” (excepted char is an unsigned type)• Set to “default value” when declare

C/C++• Separated to signed & unsigned• NO “default value”• No standard string, use char*

Type Range

char • (signed) char: -128 … 127• unsigned char: 0 … 255

short • (signed) short: -215 … (215 – 1)• unsigned short: 0 … (216 – 1)

int / long • (signed) int/long: -231 … (231 – 1)• unsigned int/long: 0 … (232 – 1)

long long • (signed) long long: -263 … (263 – 1)• usigned long long: 0 … (264 – 1)

C/C++Use sizeof() to get size of a type:

char c = 0; sizeof(c) 1

New type definition

0C/C++ only0Use typedef

typedef int Mytype;typedef int MyArr[5];

Mytype var1;MyArr arr;

C/C++

Storage class

specifiersData type

Package

Mechanism

Exception Handling

Memory managemen

tOOP

Function

Pointer

Data structure

Variable & constant

OUTLINE

Storage class specifiers

Key-work Desc. Example

auto Go out of scope once the program exits from the current block

auto int var1;int var2;

register Stored in a machine register if possible register int var;

static Allocated when the program begin and deallocated when the program ends

static int var;

extern Specify that the variable is declared in a different file. Compiler will not allocate memory for the variable

extern int DefineElseWhere;

Static / non-static

int m_iVar;static int s_StaticVar;

C/C++

Why extern?

0No need to notify compiler where is the classes/ variable/ functions

C/C++ 0MUST notify compiler where is the classes / variables/ functions were declared

0Use extern to notify that they were declared somewhere

Variable & constant Storage

class specifiers

Data type

Package

Mechanism

Exception Handling

Memory managemen

t

OOP

Function

Pointer

Data structure

OUTLINE

Variable

Local variable

Static variable

Register variable

Global variable

C/C++

Variable

C/C++

int todo(){

unsigned int Age;float a = 10;System.out.println(Age);

}

Fail, Age is not set value before using

int todo(){

unsigned int Age;float a = 10;printf("%d", Age);

}

C/C++

Age is not set value, but still OK in C/C++

Local variable

Static variable

Register variable

Global variable

No default value caused many mysterious bug

Variable0 Static duration

C/C++

static int var2;struct C { void Test(int value) { static int var; cout <<var <<endl; var = value; }};

class MyClass{public: static int s_Var;};int MyClass::s_Var = 0;

int main() { C c1, c2; c1.Test(100); c2.Test(100); var2 = 10000; MyClass::s_Var = 100;}

Local static

Global static

Set default to zerovar = 0

Value must be set outside class

definition

Static Class member

Local variable

Static variable

Register variable

Global variable

Variable

0 C/C++ only0 Stored in a machine register if

possible0 Improve performance

C/C++register int index = 0;

Local variable

Static variable

Register variable

Global variable

Variable

C/C++ only

C/C++

int globalVar = 0;int main() { int localVar = 10; cout <<globalVar <<endl; cout <<localVar <<endl;}

Local variable

Static variable

Register variable

Global variable

Constants

Use any where

Use as static data of classclass A{ final static int k_value = 0;}

const int A = 0;

C/C++

Data structure

Variable & constant

Storage class

specifiers

Data type

Package

MechanismException Handling

Memory managemen

t

OOP

Function

Pointer

OUTLINE

Data structure

class

struct

enum

C/C++

union

Data structure

0Used to set up collections of named integer constants

class

struct

enum

C/C++

union

enum MyEnumType { ALPHA, BETA, GAMMA };enum MyEnumType x; /* legal in both C and C++ */MyEnumType y; // legal only in C++

C/C++

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

Data structure

class

struct

enum

C/C++

union

class JavaClass{ public JavaClass() {…} private void Toso() {…} }

class CClass{ public: CClass() {…} ~CClass(); private: void Toso() ;};

#include "Any_name.h" void CClass::Todo(){ …}CClass::~CClass(){ …}

JavaClass.java

Any_name.h Other_name.cpp

C/C++

Data structure0 C/C++ only0 A user-defined type that uses same

block of memory for every its list member.

class

struct

enum

C/C++

union union NumericType{ int iValue; long longValue; double dValue; };

int main(){ union NumericType Values = { 10 }; // iValue = 10 printf_s("%d\n", Values.iValue); Values.dValue = 3.1416; printf_s("%f\n", Values.dValue);} C/C++

0 4 8

iValuelongValue

dValue

Data structure0 C/C++ only0 The C++ class is an extension of the C

language structure0 Default access:

0 Class: private0 Struct: public

class

struct

enum

C/C++

unionclass X { // private by default int a;public: // public member function int f() { return a = 5; };};

struct Y { // public by default int f() { return a = 5; };private: // private data member int a;};

Should be used for storing only.

C/C++See more: structure alignment

Pointer

Data structure

Variable & constant

Storage class

specifiers

Data type

PackageMechanism

Exception Handling

Memory managemen

t

OOP

Function

OUTLINE

Pointer0 No explicit pointer in Java0 Array and object are implicit pointer0 Explicit null value for array/object

C/C++

Bicycle bike1 = new Bicycle();int[] arr = new int [100]

bike1

arr

Two type of variable: o Data type

o Pointer type Implicit null value, aka zero value (0)

int i;int *p = &i;char *st = new char[10];char *p2 = st;char st2[] = "ABC“;char p3[] = st2;

i p st2 = ABC st p2

null

0x0 NULL

sizeof(p) = ?sizeof(st2) = ?

p = ?*p = ?&p = ?

String

0No standard string in C/C++0Use char*, or char[] instead0String in C/C++ is array of byte, end with ‘\0’

char *st = "String";

S t r i n g \0st

char st2[] = "String";

S t r i n g \0

st2

st = ?&st = ?*st = ?

st2 = ?&st2 = ?*st2 = ?

Function pointer0 C/C++ only0 Is variable store address of a function

// C void DoIt (float a, char b, char c){……}void (*pt2Function)(float, char, char) = DoIt;

// usingpt2Function(0, 0, 0);

// C++class TMyClass{public: void DoIt(float a, char b, char c){……};};void (TMyClass::*pt2Member)(float, char, char) = &TMyClass::DoIt;

// usingTMyClass *c = new TMyClass();(c->*pt2Member)(0, 0, 0); C/C++

Object0Always use “new”0Object variable hold reference

C/C++

0 Support two kinds:0 Object variable hold values

0 Object variable hold reference (through pointer)

Bicycle bike1 = new Bicycle();bike1.changeCadence(50);

Bicycle bike1; bike1.changeCadence(50);

Bicycle *bike2 = new Bicycle(); bike2->changeCadence(50);(*bike2).changeCadence(100);

bike1 vs. bike2?

Function

Pointer

Data structure

Variable & constant

Storage class

specifiers

Data typePackage

Mechanism

Exception Handling

Memory managemen

t

OOP

OUTLINE

Function

C/C++

• Declare inside class• Pass-by-value only• No need prototype

• Declare anywhere• Pass-by-value / pass-by-reference optional• Need prototype

How about array and

object?

Function

0Function Prototypevoid todo();void main(){ todo();}void todo(){ ……}

0Pass by value / Pass by referencevoid todo(int pass_by_value, int &pass_by_ref)

“&” is for pass by reference

prototype

C/C++

Pass-by-valueC/C++

void swap1(int i, int j) void swap1(int i, int j)void swap1(MyClass obj1, MyClass obj2)

 

B’

swap

B

A

A’

B’

A’

 

 

 

B

A

tmp = A;A = B;B = tmp

Pass-by-value (2)

 

 

A’

B’ 

A’

B’

A

B

A

B

Copy value (addr. of data)

swap2

 

C/C++void swap2(MyClass obj, MyClass obj2) void swap2(MyClass* obj, MyClass* obj)

tmp = A;A = B;B = tmp

Pass-by-ref

void swap3(MyClass &obj1, MyClass &obj2)

Not available

C/C++

 

B

swap

B

A

A

B

A

B

A

 

 

 tmp = A;A = B;B = tmp

OOP

Function

Pointer

Data structure

Variable & constant

Storage class

specifiersData type

Package

Mechanism

Exception Handling

Memory managemen

t

OUTLINE

OOP

Interface

Pure virtual class

C/C++

Abstract class

Single inheritance

Multiple inheritance

Constructor

Destructor

super

virtual

Pure virtual function

public private

protected

friend

OOP Theory

final

OOP - Inheritancepublic class MyDog extends Dog implement ITalkable, ISmileble{public:

MyDog(){}//ITalkable implementvoid DoTalk();//ISmileblevoid DoSmile();void Todo() { super.Todo();}

}

C/C++

public class MyDog:public Dog,public ITalkable, protected ISmileble{public:

MyDog(){}~MyDog() {}//ITalkable implementvoid DoTalk();//ISmileblevoid DoSmile();void Todo() { Dog::Todo();}

}

Destructor, called when object is deallocated

OOPAbstract class vs. Pure virtual class

public abstract class GraphicObject { // declare fields // declare non-abstract methods abstract void draw();}

C/C++

class classname{ public:

virtual void virtualfunctioname() = 0;};

Pure virtual function

OOP - virtual

• Function are virtual by default• Use final to prevent override

C/C++

• Use key word virtualvirtual int foo()

class ClassA{public:

ClassA() {}virtual void Todo();

};

class ClassB: public ClassA{public:

ClassB():ClassA() {}void Todo();

}

OOP - virtual

class ClassA{public:

ClassA() {}virtual void Todo1() {printf("TodoA1\n");}void Todo2() {printf("TodoA2\n");}

};

class ClassB: public ClassA{public:

ClassB():ClassA() {}void Todo1() {printf("TodoB1\n");}void Todo2() {printf("TodoB2\n");}

};

void main(){

ClassA *Obj = new ClassB();Obj->Todo1();Obj->Todo2();

} C/C++

Output ?

OOP – virtual destructor

class ClassA{public:

ClassA() {}virtual ~ClassA() {printf("DeleteA\n");}

};

class ClassB: public ClassA{public:

ClassB():ClassA() {}~ClassB() {printf("DeleteB\n");}

};

void main(){

ClassA *Obj = new ClassB();delete Obj;

} C/C++

Without virtual, only destructor of ClassA is called

Memory managemen

tOOP

Function

Pointer

Data structure

Variable & constant

Storage class

specifiers

Data type

Package

Mechanism

Exception Handling

OUTLINE

#define NULL 0int main() { // Allocate memory for the array char* pCharArray = new char[100]; // Deallocate memory for the array delete [] pCharArray; pCharArray = NULL;

// Allocate memory for the object CName* pName = new CName; pName->SetName("John");

// Deallocate memory for the object delete pName; pName = NULL;}

Memory management

C/C++

Use GC to collect garbage data

• No GC mechanism, handle manually• Use delete / free to clean up

unused heap• Memory leak problem

C/C++

Exception Handling Memory

management

OOP

Function

Pointer

Data structure

Variable & constant

Storage class

specifiers

Data type

Package

Mechanism

OUTLINE

Exception handling

Well supported build in exception

try{ int zero = 0; int val = 1/zero;}catch (Exception E){ E.printStackTrace();}

C/C++Manual exception handling

class DBZEx {};void div(int num1, int num2){ if (num2 == 0) throw (DBZEx ());}void main(){ try { div(1, 0); } catch (DBZEx ex) { printf(" DBZ Exception "); } catch (...) { printf("Unkown exception"); }}

The end!

Appendix A: Preprocessor

Appendix A: preprocessor

0Handle directive: #include0Macro definition: #define, #undef0Condition inclusion: #if, #ifdef, #ifndef, #if defined(…), #elif, #else, #endif

0Refs:0 http://en.wikipedia.org/wiki/C_preprocessor0 http://msdn.microsoft.com/en-us/library/b0084kay.aspx0 http://gcc.gnu.org/onlinedocs/cpp/index.html0 http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf

Appendix A: preprocessor

#include0 Include another file.

#include <stdio.h> int main (void){ printf("Hello, world!\n"); return 0;}

The preprocessor replaces the line #include <stdio.h> with the system header file of that name

Appendix A: preprocessor

#define0 Define a macro, object-like and function-like

#define Min(x, y) ((x)<(y))?(x):(y)

Object-like #define PI 3.14

Function - like

#define PI 3.14#define Min(x, y)((x)<(y))?(x):(y)void main(){

int pi = PI;int num = Min(pi, 2);

}

#undef0 Un-defined a macro

Appendix A: preprocessor

#if, #ifdef, #ifndef, #if defined(…)#elif, #else, #endif

0 Directives can be used for conditional compilation.

#ifdef _WIN32# include <windows.h> #else # include <unistd.h> #endif

#if VERBOSE >= 2 print("trace message");

#endif

#if !defined(WIN32) || defined(__MINGW32__) ... #endif

Prevent duplicate declaration

void Todo();//something else

H1.h

#include "H1.h"//something else

H2.h

#include "H1.h"#include "H2.h"

//something else

Main.cpp

//from H1void Todo();

H2.h preprocess

//from H1void Todo();

//from H2void Todo();

//something else

Main.cpp preprocess

duplicated

Prevent duplicate declaration

0Use #ifndef

#ifndef __H1_H__#define __H1_H__

void Todo();//something else

#endif

H1.h

#pragma once

void Todo();//something else

H1.h

0 Use #pragma once