在静态方法中复制局部变量

Question

在我的脑海中，我正在初始化一个名为grade的变量，并使用if else语句来更改变量。 但是我收到重复的局部变量错误。我返回双倍，所以我初始化为 0.0。我在这里理解"范围"是错误的吗？

public static double finalGrade(double assignment, double midterm, double finalExam) {
double grade=0.0;
double midWorth = divide(midterm,20);
double finalWorth = divide(finalExam,45);
if(finalWorth < midWorth) {
double grade = divide((assignment + finalExam),80); 
}
else  {
double grade = divide((assignment + midterm + finalExam), 100);
}
return grade;
}

Answer 1

声明变量时，只需指定数据类型double一次。更新值时无需。

---

有代码是这样的，

public static double finalGrade(double assignment, double midterm, double finalExam) {
double grade=0.0; // declaring
double midWorth = divide(midterm,20);
double finalWorth = divide(finalExam,45);
if(finalWorth < midWorth) {
grade = divide((assignment + finalExam),80); // updating value
} else  {
grade = divide((assignment + midterm + finalExam), 100); // updating value
}
return grade;
}

Answer 2

考虑变量的作用域

在

if(finalWorth < midWorth) {
double grade = divide((assignment + finalExam),80); 
}
else  {
double grade = divide((assignment + midterm + finalExam), 100);
}

if-else中grade变量的作用域仅限于if-else- 在大括号外不可见

所以做

if(finalWorth < midWorth) {
grade = divide((assignment + finalExam),80); 
}
else  {
grade = divide((assignment + midterm + finalExam), 100);
}