編寫一個類Calculator,有兩個屬性num1,num2,這兩個數據的值，不能在定義的同時初始化，最后實現加減乘除四種運算.

public?class?HomeWork?{
	public?static?void?main(String[]?args)?{
		Scanner?scan0?=?new?Scanner(System.in);
		Scanner?scan1?=?new?Scanner(System.in);
		while(true)?{
			int?x?=?scan0.nextInt();
			int?y?=?scan1.nextInt();
			Calculator?calculator?=?new?Calculator(x,?y);
			System.out.println(x?+?"?+?"?+?y?+?"=?"?+?calculator.add());
			System.out.println(x?+?"?-?"?+?y?+?"=?"?+?calculator.sub());
			System.out.println(x?+?"?*?"?+?y?+?"=?"?+?calculator.mul());
			System.out.println(x?+?"?/?"?+?y?+?"=?"?+?calculator.dev());
		}
	}
}
class?Calculator?{
	private??int?num1;
	private??int?num2;
	public?int?add()?{
		return?this.num1?+this.num2;
	}
	public?int?sub()?{
		return?this.num1?-this.num2;
	}
	public?int?mul()?{
		return?this.num1?*this.num2;
	}
	public?double?dev()?{
		double?ret?=?(double)this.num1?/?this.num2;
		return?ret;
	}
	public?Calculator(int?num1,?int?num2)?{
		this.num1?=?num1;
		this.num2?=?num2;
	}
}

實現交換兩個變量的值。要求:需要交換實參的值

public?class?HomeWork0?{
	public?static?void?main(String[]?args)?{
		System.out.println("第一種");
		int[]?arr?=?{10,20};
		System.out.println("交換前"+Arrays.toString(arr));
		swap(arr);
		System.out.println("交換后"+Arrays.toString(arr));

		System.out.println();

		System.out.println("第二種");
		MyValue?myValue1?=?new?MyValue();
		myValue1.val?=?1;
		MyValue?myValue2?=?new?MyValue();
		myValue2.val?=?2;
		System.out.println("交換前:?"+myValue1.val+"?"+myValue2.val);
		swap(myValue1,myValue2);
		System.out.println("交換后:?"+myValue1.val+"?"+myValue2.val);

	}
	public?static?void?swap(MyValue?myValue1,MyValue?myValue2)?{
		int?tmp?=?myValue1.val;
		myValue1.val?=?myValue2.val;
		myValue2.val?=?tmp;
	}
	public?static?void?swap(int[]?arr)?{
		int?tmp?=?arr[0];
		arr[0]?=?arr[1];
		arr[1]?=?tmp;
	}
}
class?MyValue?{
	public?int?val;
}

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