Why can't variables be declared in an if statement?

Question

The following Java code does not compile.

int a = 0;

if(a == 1) {
    int b = 0;
}

if(a == 1) {
    b = 1;
}

Why? There can be no code pa

Answer 1

Just for completeness sake: this one works as well (explanation is scoping, see the other answers)

int a = 0;

if(a == 1) {
    int b = 0;
}

if(a == 1) {
    int b = 1;
}

Due to scoping, b will only be accessible inside the if statements. What we have here are actually two variables, each of which is just accessible in their scope.