Java Object数组java.lang.NullPointerException [英] Java Object array java.lang.NullPointerException

问题描述

我遇到了一个问题，我创建了一个对象数组，但是当我尝试解决某些问题时，我得到了一个 java.lang.NullPointerException 。

I am having a problem where I create an array of objects but I get a java.lang.NullPointerException when i try to address something to it.

这是有问题的类。

public class Blocks {
public static Block[] b = new Block[8];

public Blocks() throws IOException {
    new Air  (b[0]);
    new Stone(b[1]);
    new Grass(b[2]);
    new Dirt (b[3]);
}

这是类Block。

public class Block {
private Texture Texture = null;
private int S = World.BLOCK_SIZE;
private boolean hasTexture = true;
private String texturePath = null;

public void setTexture(String path) throws IOException {
    this.texturePath = path;
    Texture = TextureLoader.getTexture("PNG", new FileInputStream(new File(path)));
}

public void draw(int Xa, int Ya) {

    GL11.glTranslatef(Xa, Ya, 0);
    //GL11.glRotatef(0, 0, 1, 0);
    //GL11.glRotatef(0, 1, 0, 0);

    if(hasTexture) {
    Texture.bind();

    GL11.glBegin(GL11.GL_QUADS);
        GL11.glColor3f(0.5f, 0.5f, 1);
        //GL11.glNormal3f(0, 0, 1);
        GL11.glTexCoord2f(0, 0);
        GL11.glVertex2f(0, 0);
        GL11.glTexCoord2f(0, 1);
        GL11.glVertex2f(0, S);
        GL11.glTexCoord2f(1, 1);
        GL11.glVertex2f(S, S);
        GL11.glTexCoord2f(1, 0);
        GL11.glVertex2f(S, 0);

        GL11.glEnd();
    }
}

void hasTexture(boolean b) {
    this.hasTexture = b;
}

}

如果需要，请告诉我提供更多信息/代码

please let me know if i need to provide more info/code

推荐答案

这样做

public class Blocks {
public static Block[] b = new Block[8];

static {
   // Instantiating the objects present in the array
   for(int i=0; i<b.length; i++)
       b[i] = new Block();
}

public Blocks() throws IOException {
   // Now you can access them
    new Air  (b[0]);
    new Stone(b[1]);
    new Grass(b[2]);
    new Dirt (b[3]);
}

您忘记实例化数组中的对象。所以它提示空指针异常

You forgot to instantiate the objects present in the array. So it is prompting null pointer exception

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