[小小測試] C/C++ 與 Java、struct 與 class 用法比較

 附錄：

C 的 struct

#include <stdio.h>
#include <stdlib.h>

typedef struct
{
    int len;
    int width;
}Rectangle;

int main()
{
    Rectangle r1;
    r1.len=5;
    r1.width=10;
    printf("Len=%d\n", r1.len);
    printf("Width=%d\n", r1.width);
    printf("Area=%d\n", r1.len*r1.width);

    // system("pause");
    return 0;
}

執行結果：

Len=5
Width=10
Area=50

C++ 的 struct

#include <iostream>
#include <stdlib.h>

using namespace std;

typedef struct
{
    int len;
    int width;
}Rectangle;

int main()
{
    Rectangle r1;
    r1.len=5;
    r1.width=10;
    cout << "Len=\t" << r1.len << '\n';
    cout << "Width=\t" << r1.width << '\n';
    cout << "Area=\t" << r1.len*r1.width << '\n';

    // system("pause");
    return 0;
}

執行結果：

Len=5
Width=10
Area=50

Java 的 Class

package jClass;

public class Rectangle
{
    public int len;
    public int width;

    public int area()
    {
        return len * width;
    }
}

主程式

package jClass;

public class jClass
{
    public static void main(String[] arg)
    {
        Rectangle r1 = new Rectangle();
        
        r1.len=5;
        r1.width=10;
        
        System.out.println("Len=\t" + r1.len);
        System.out.println("Width=\t" + r1.width);
        System.out.println("Area=\t" + r1.area());
    }
}

執行結果：

Len=5
Width=10
Area=50

咦~ C++ 的 class 呢？別急，馬上就來！

C++ 的 class

#include <iostream>
#include <stdlib.h>
using namespace std;

class Rectangle
{
public:
    int len;
    int width;

    int area()
    {
        return len*width;
    }
};  ///  <==這裡的';'絕對不能忘記;

int main()
{
    Rectangle r1;
    r1.len=5;
    r1.width=10;
    cout << "Len=\t" << r1.len << '\n';
    cout << "Width=\t" << r1.width << '\n';
    cout << "Area=\t" << r1.area() << '\n';

    //system("pause");
    return 0;
}

執行結果：

Len=5
Width=10
Area=50

參考資料：

What are POD types in C++? – StackOverflow

Creating an instance of class – StakOverflow

When should you use a class vs a struct in C++? – StackOverflow

C/C++ Struct vs Class – StackOverflow

C++ 學習筆記 – openhome.cc

How do you implement a class in C? – StackOverflow

C++ Class access modifiers – TutorialsPoint

程式語言教學誌: Java 快速導覽 – 物件導向概念 封裝與存取權限

C++ Class Constructor and Destructor – TutorialsPoint