这两种方法有什么区别？

Question

Method number 1:

public void setAge(int newAge){
    age = newAge;
}

Method number 2

public void setAge (int age){
    this.age = age;
}

Answer 1

In both, it must be assumed that the object has a field called age .

Second Version

In the second one, there is also a parameter called age . Since the parameter age has the same name as the field age , it " hides " the field. So, within the second version, anywhere you see age will be referring to the parameter, not the field.

Since the field is hidden, you need a way to still access it. You can still get at it by using the this reference. this refers to "this" object, and this.age accesses the field instead of the parameter. So field this.age is set to parameter age .

First Version

The first version just avoids this ambiguity by using a different parameter name so that the field is not hidden , so it still sets field age to the parameter but does not need the this. prefix .

Answer 2

两者都是setter方法，这是将值分配给类内的私有变量的通用约定，这两种方法具有相同的功能，第一种方法是将值分配给称为age的类字段，而第二种方法也将值分配给相同的变量，但该变量是由年龄参数阴影，因为他们的名字是一样的，所以要改变字段age而不是仅仅在函数内部可用的本地参数，你需要使用this.age这意味着你要改变字段而不是局部变量。

Answer 3

In the first case, it is clear both variables are different, so no problem.

But in the second case which age you are explicitly specifying which age you are referring to and it is a good practice. We add this.age so that compiler knows you are referring to class variable not local variable in left side and right side local variable age

Answer 4

Considering that setAge function is a member function of a class that has a member variable age : Both codes will change the value of age to the argument passed to the function.

Having said that, second method is considered a good practice where you are explicitly specifying that you want to change the member variable of the current object by using this keyword.

Answer 5

I think that age is a member of the class you use. In this case in second method the argument got a same name as member class so you need to use this specifier inside a method to specify that you want to assign a new value to a class member.

Answer 6

Both methods are the same, will do same thing, but standard is to use

public void setAge (int age){
     this.age = age;
}

with "this.age" (this-meaning the age of your object) and with the same parameter name as the field.