英文:
When we create a setter method in java , how does java know to which variable we want to set the given value from the setter ? read discription please
问题
在我提供的图片中，您可以看到我创建了一个名为"employee"的类，其中包含一个未赋值的变量。我还提供了getter和setter方法。现在我有一个问题，就是在setter方法（即"setsalary"）中，我将一个整数值存储在变量"s"中，然后将其赋值给"salary"变量。现在，当我创建该特定类的一个对象（如您在图片中看到的），程序如何知道将给定的工资值赋值给对象的工资，即（John.salary）？我的意思是，我只写了"salary=s;"，没有其他操作。程序如何确切地将值设置到对象中？
（图片已略去）
英文:
In my given Image you can see that I have created a Class named employee with one variable with no assigned value.Also I have given getter and setter methods. Now the queston i have is that , in the Setter method i.e (setsalary) , I am taking a integer value into the variable s and then assigning it to the salary variable. Now when I create an object of that particular class ( as you can see in the image), how does the program knows that the given value of salary has to be assigned to the salary of the object i.e (John.salary) , I mean i have only written salary=s; and nothing else. How does the program setts the value exactly to the object ?
答案1
得分: 1
缺失的关键是this 关键字：
在实例方法或构造函数内部，this 是对当前对象的引用 — 即调用该方法或构造函数的对象。您可以通过使用 this 在实例方法或构造函数内部引用当前对象的任何成员。
没有在那里写的是 this 关键字是可选的，因此这行代码：
salary=s;
和这行代码是等价的：
this.salary=s;
因此它知道要使用哪个实例（在此情况下为 John），因为实际上在 "salary" 前面有一个看不见的 "this"，告诉它要赋值给当前对象。
英文:
> how does the program knows that the given value of salary has to be
> assigned to the salary of the object i.e (John.salary) , I mean i have
> only written salary=s; and nothing else
The missing ingredient is the this keyword:
> Within an instance method or a constructor, this is a reference to the
> current object — the object whose method or constructor is being
> called. You can refer to any member of the current object from within
> an instance method or a constructor by using this.
What isn't written there is that the this keyword is OPTIONAL, thus this line:
salary=s;
and this line are equivalent:
this.salary=s;
So it knows which instance (John in this case) to use because there is actually an invisible "this" in front of "salary" telling it to assign to the CURRENT OBJECT.
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