[JAVA]物件的等於

對於以前在學校寫C之後，
等於(=)這個符號的概念一直都是把左邊的值賦予給右邊的值




例如:

	#include <iostream>
	using namespace std;
	int main()
	{
	int a = 1;
	int b = 2;
	a = b;
	b = 3;
	cout<<"a = "<<a<<endl;
	return 0;
	}

view raw cplus_equal.cpp hosted with ❤ by GitHub

int a = 1;
int b = 2;

a = b; //b的值2給了a
b = 3; //之後值3給了b

結果a印出來是2， b是3


但是在java中，物件的等於是有pointer的含意在的，
假設我封裝了int的物件專門存int

	class Int {
	int value;
	public Int(int value){
	this.value = value;
	}
	public void setInt(int value){
	this.value = value;
	}
	public int getInt(){
	return value;
	}
	}

view raw Int.java hosted with ❤ by GitHub

這樣的寫法

Int A = new Int(1);
Int B = new Int(2); A = B; //B被指定的new Int(2)的這個物件,指定給A控制 

B.setInt(3);//B被指定的new Int(2)的這個物件,現在值3給了這個物件,A擁有這個物件所以值也變成3,b也是3

以下是java程式碼以供比較,基本上值的等於用法跟C++一樣沒變,只有物件不一樣要注意

	import java.io.Console;
	class Demo {
	public static void main(String[] args) {
	int a = 1;
	int b = 2;
	a = b;
	b = 3;
	System.out.println("int結果"+a);
	Int A = new Int(1);
	Int B = new Int(2);
	A = B;
	B.setInt(3);
	System.out.println("int物件結果"+a.getInt());
	}
	}

view raw java_equal.java hosted with ❤ by GitHub

還有C++版本

	#include <iostream>
	using namespace std;
	int main()
	{
	int a = 1;
	int b = 2;
	a = b;
	b = 3;
	cout<<"a = "<<a<<endl;
	return 0;
	}

view raw cplus_equal.cpp hosted with ❤ by GitHub