MatParamTexture: duplicate variables, missing javadoc, exceptions (#2243)

* MatParamTexture: duplicate variables, missing javadoc, setValue to null throws exception

This PR solves all the problems listed above.

* removal of setValue() override method

* javadoc

jme3-core/src/main/java/com/jme3/material/MatParamTexture.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2021 jMonkeyEngine
+ * Copyright (c) 2009-2024 jMonkeyEngine
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -40,51 +40,67 @@ import com.jme3.texture.Texture;
 import com.jme3.texture.image.ColorSpace;
 import java.io.IOException;
 
+/**
+ * A material parameter that holds a reference to a texture and its required color space.
+ * This class extends {@link MatParam} to provide texture specific functionalities.
+ */
 public class MatParamTexture extends MatParam {
 
-    private Texture texture;
     private ColorSpace colorSpace;
 
+    /**
+     * Constructs a new MatParamTexture instance with the specified type, name,
+     * texture, and color space.
+     *
+     * @param type       the type of the material parameter
+     * @param name       the name of the parameter
+     * @param texture    the texture associated with this parameter
+     * @param colorSpace the required color space for the texture
+     */
     public MatParamTexture(VarType type, String name, Texture texture, ColorSpace colorSpace) {
         super(type, name, texture);
-        this.texture = texture;
         this.colorSpace = colorSpace;
     }
 
+    /**
+     * Serialization only. Do not use.
+     */
     public MatParamTexture() {
     }
 
+    /**
+     * Retrieves the texture associated with this material parameter.
+     *
+     * @return the texture object
+     */
     public Texture getTextureValue() {
-        return texture;
+        return (Texture) getValue();
     }
 
+    /**
+     * Sets the texture associated with this material parameter.
+     *
+     * @param value the texture object to set
+     * @throws RuntimeException if the provided value is not a {@link Texture}
+     */
     public void setTextureValue(Texture value) {
-        this.value = value;
-        this.texture = value;
-    }
-    
-    @Override
-    public void setValue(Object value) {
-        if (!(value instanceof Texture)) {
-            throw new IllegalArgumentException("value must be a texture object");
-        }
-        this.value = value;
-        this.texture = (Texture) value;
+        setValue(value);
     }
 
     /**
+     * Gets the required color space for this texture parameter.
      * 
-     * @return the color space required by this texture param
+     * @return the required color space ({@link ColorSpace})
      */
     public ColorSpace getColorSpace() {
         return colorSpace;
     }
 
     /**
-     * Set to {@link ColorSpace#Linear} if the texture color space has to be forced to linear 
-     * instead of sRGB
+     * Set to {@link ColorSpace#Linear} if the texture color space has to be forced
+     * to linear instead of sRGB.
+     * 
      * @param colorSpace the desired color space
-     * @see ColorSpace
      */
     public void setColorSpace(ColorSpace colorSpace) {
         this.colorSpace = colorSpace;
@@ -94,17 +110,17 @@ public class MatParamTexture extends MatParam {
     public void write(JmeExporter ex) throws IOException {
         super.write(ex);
         OutputCapsule oc = ex.getCapsule(this);
-        oc.write(0, "texture_unit", -1);
-        oc.write(texture, "texture", null); // For backwards compatibility
-
         oc.write(colorSpace, "colorSpace", null);
+        // For backwards compatibility
+        oc.write(0, "texture_unit", -1);
+        oc.write((Texture) value, "texture", null);
     }
 
     @Override
     public void read(JmeImporter im) throws IOException {
         super.read(im);
         InputCapsule ic = im.getCapsule(this);
-        texture = (Texture) value;
         colorSpace = ic.readEnum("colorSpace", ColorSpace.class, null);
     }
-}
+    
+}