public void setMode(int mode) throws Exception {
        if (mode != ADDITION && mode != SUBTRACTION) {
            throw new Exception("Invalid mode");
        }
        this.mode = mode;
    }
<code>setMode</code> sets the mode of the combiner. This may either
be ADDITION or SUBTRACTION.
@param mode the mode of the combiner.
@throws Exception if mode is not ADDITION or SUBTRACTION.
jme3-terrain/src/main/java/com/jme3/terrain/heightmap/CombinerHeightMap.java