在条件内重新分配Java变量

Question

I've got a variable, which is initialized and then dynamically reassigned in a conditional; as such:

int a;

if(b > 5) {
    int a = 10;
} else {
    int a = 1;
}

It gives me this error:

/path/to/file:4 a is already defined in int a = null;

Why can't I reassign this variable?

Answer 1

When you write

int a;

this is the declaration of variable. And if you try to again write it the same way in the same scope and as the variable already exists so compiler throws an error.

You need not to re-define the variable a , just re-assign it like this:

int a = 0; // note that you need to initialize the local variables before using 

if(b > 5) {
     a = 10;
} else {
     a = 1;
}

Answer 2

You're actually redeclaring variable a , not reassigning its value.

Try

a = 10;

instead of

int a = 10;

Answer 3

是时候使用嵌入式条件运算符（“三元运算符”）了：

 int a = (b > 5) ? 10 : 1;