Java: “Local variable may not have been initialize

问题:

Consider the following method:

void a ()
{
    int x;
    boolean b = false;
    if (Math.random() < 0.5)
    {
        x = 0;
        b = true;
    }
    if (b)
        x++;
}

On x++ I get the "Local variable may not have been initialized" error. Clearly x will never be used uninitialized. Is there any way to suppress the warning except by initializing x? Thanks.

回答1:

No, there is no way Java can examine all possible code paths for a program to determine if a variable has been initialized or not, so it takes the safe route and warns you.

So no, you will have to initialize your variable to get rid of this.

回答2:

There is one :

void a () {
    if (Math.random() < 0.5) {
        int x = 1;
    }
}

The compiler isn't responsible for devising and testing the algorithm. You are.

But maybe you should propose a more practical use case. Your example doesn't really show what's your goal.

回答3:

Why don't you simply use

void a ()
{
    int x;
    boolean b = false;
    if (Math.random() < 0.5)
    {
        x = 0;
        b = true;
        x++;
    }
    if (b) {
        //do something else which does not use x
    }
}

In the code why do you want to use x outside the first if block, all the logic involving x can be implemented in the first if block only, i don't see a case where you would need to use the other if block to use x.

EDIT: or You can also use:

void a ()
{
    int x;
    boolean b = (Math.random() < 0.5);
    if (b) {
         x=1
        //do something 
    }
}