为什么简单布尔值的 if/else if/else 没有给出“无法访问的代码"?错误
为什么这段代码没有给出无法访问的代码"错误?因为布尔值只能是真或假.
Why is this code not giving an "unreachable code" error? Since a boolean can only be true or false.
public static void main(String args[]) {
boolean a = false;
if (a == true) {
} else if (a == false) {
} else {
int c = 0;
c = c + 1;
}
}
推荐答案
来自 JLS 14.21.无法访问的语句
如果由于无法访问而无法执行语句，则为编译时错误.
It is a compile-time error if a statement cannot be executed because it is unreachable.
和
如果 if-then-else 语句可达，则 else 语句可达.
The else-statement is reachable iff the if-then-else statement is reachable.
您的 if-then-else 语句是可访问的.因此，根据定义，编译器认为 else 语句是可访问的.
Your if-then-else statement is reachable. So, by the definition the compiler thinks that the else-statement is reachable.
注意:有趣的是，下面的代码也可以编译
Note: Interestingly the following code also compiles
// This is ok
if (false) { /* do something */ }
这不适用于 while
// This will not compile
while (false) { /* do something */ }
因为 while 的可达性定义不同(强调我的):
because the reachability definition for while is different (emphasis mine):
如果while语句可达且条件表达式不是值为false的常量表达式，则包含的语句是可达的.
The contained statement is reachable iff the while statement is reachable and the condition expression is not a constant expression whose value is false.
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