Conditional Execution - Building Java Programs: A Back to Basics Approach - page 237

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}
if (score >= 80) {
grade = "B";
}
if (score >= 70) {
grade = "C";
}
if (score >= 60) {
grade = "D";
}
if (score < 60) {
grade = "F";
}
However, if you then try to use the variable grade after this code, you'll get
this error from the compiler:
variable grade might not have been initialized
This is a clue that there is a problem. The Java compiler is saying that it
believes there are paths through this code that will leave the variable grade
uninitialized. In fact, the variable will always be initialized, but the compiler can-
not figure this out. We can fix this problem by giving an initial value to grade :
String grade = "no grade";
This change allows the code to compile. But if you compile and run the pro-
gram, you will find that it gives out only two grades: D and F. Anyone who has a
score of at least 60 ends up with a D and anyone with a grade below 60 ends up
with an F. And even though the compiler complained that there was a path that
would allow grade not to be initialized, no one ever gets a grade of “no grade.”
The problem here is that you want to execute exactly one of the assignment
statements, but when you use sequential if statements, it's possible for the pro-
gram to execute several of them sequentially. For example, if a student has a score
of 95, that student's grade is set to "A" , then reset to "B" , then reset to "C" , and
finally reset to "D" . You can fix this problem by using a nested if/else construct:
String grade;
if (score >= 90) {
grade = "A";
} else if (score >= 80) {
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