尝试从 Java 中的方法返回 float[]

Question

I'm writing a game and working on collisions. Currently, I'm trying to use the tileCollision function to return a 1-dimensional array containing 2 numbers; the coordinates of the corner. (represented in the program by cX and cY)

I expected this to run smoothly: that is, to return {-999, -999} if it wasn't colliding, and to return a valid set of coordinates otherwise. Unfortunately, IntelliJ tells me that the goodCX and goodCY variables "might not have been initialised" which I do not know how to solve. Running the program gives me the same error.

The Tile class can be treated as a class containing an X value, a Y value, and a texture. The t.texture.width & t.texture.height should be set to 50 to make it simpler to understand. Entity can be assumed as a class containing variables named x, y, vx, vy, and a "texture" whose dimensions should be 20x20. I use Java with the Processing 3 library to render my code and am happy to provide extra info if needed.

The main problem is less with those rather than the "might not have been initialised" problem, though.

Please, go easy on me, and if possible, don't use anything wildly outside the realm of what is demonstrated in my code. I am an amateur programmer, and while I have been programming for a while, am not exactly professional.

Here's my code:

public float[] tileCollision(Tile t)
{
    boolean isCollide = false;

    float tX = t.eX;
    float tX2 = t.eX + t.texture.width;
    float tY = t.eY;
    float tY2 = t.eY + t.texture.height;

    float[] cX = new float[]{this.x + this.vx, this.x + this.texture.width + this.vx};
    float[] cY = new float[]{this.y + this.vy, this.y + this.texture.height + this.vy};

    float[] bad = new float[]{-999, -999};

    float goodCX, goodCY;

    System.out.println("\nCollisions Testing Names:");
    System.out.println(this);
    System.out.println(t);

    for(int i = 0; i < 2; i ++)
    {
        for(int i_ = 0; i_ < 2; i_ ++)
        {
            System.out.println("\nCollisions Testing:");
            System.out.println("Entity X: " + cX[i]);
            System.out.println("Entity Y: " + cY[i_]);

            System.out.println("Tile Xs: " + tX + ", " + tX2);
            System.out.println("Tile Ys: " + tY + ", " + tY2);

            if( ( (tX <= cX[i]) && (cX[i] <= tX2) ) && ( (tY <= cY[i_]) && (cY[i_] <= tY2) ) )
            {
                isCollide = true;

                goodCX = cX[i];
                goodCY = cY[i_];
            }
        }
    }

    System.out.println("Am I colliding?\n>>> " + isCollide);

    if(isCollide)
    {
        return new float[]{goodCX, goodCY};
    }
    else { return(bad); }
}

Answer 1

The problem resides in the fact that you only assign (and first-assign, and hence, initialize) your goodCX and goodCY variables inside a complex if nested inside your for loops. Then, if(isCollide) , you will attempt to return them, but there is no way the compiler can infer any kind of connection between the complex if condition you have, and the isCollide condition, so you may be returning unassigned references.

To resolve this, simply make a default initialization of your float references at the top, as follows:

float goodCX = 0.0;
float goodCY = 0.0;

Answer 2

If the collision check do not evaluate true GoodCX and GoodCY will never be initialized. You will have problems trying to return "new float[]{goodCX, goodCY}". Try initializing your GoodCX and GoodCY with -999. You will also be able to simplify your code with that:

public float[] tileCollision(Tile t)
{
    boolean isCollide = false;

    float tX = t.eX;
    float tX2 = t.eX + t.texture.width;
    float tY = t.eY;
    float tY2 = t.eY + t.texture.height;

    float[] cX = new float[]{this.x + this.vx, this.x + this.texture.width + this.vx};
    float[] cY = new float[]{this.y + this.vy, this.y + this.texture.height + this.vy};



    float goodCX = -999;
    float goodCY = -999;

    System.out.println("\nCollisions Testing Names:");
    System.out.println(this);
    System.out.println(t);

    for(int i = 0; i < 2; i ++)
    {
        for(int i_ = 0; i_ < 2; i_ ++)
        {
            System.out.println("\nCollisions Testing:");
            System.out.println("Entity X: " + cX[i]);
            System.out.println("Entity Y: " + cY[i_]);

            System.out.println("Tile Xs: " + tX + ", " + tX2);
            System.out.println("Tile Ys: " + tY + ", " + tY2);

            if( ( (tX <= cX[i]) && (cX[i] <= tX2) ) && ( (tY <= cY[i_]) && (cY[i_] <= tY2) ) )
            {
                goodCX = cX[i];
                goodCY = cY[i_];
            }
        }
    }

    return new float[]{goodCX, goodCY};
}

Answer 3

Intellij is giving you that response because the variables are declared but not initialized. You need to define them with some default state or modify the code that follows to ensure they're initialized.