Replaced all instances of Guava's Optional type with Java 8's Optional type, as discussed in #81. (#90)

src/main/java/appeng/entity/EntityChargedQuartz.java

@@ -153,12 +153,12 @@ public final class EntityChargedQuartz extends AEBaseEntityItem
 					netherQuartz.setDead();
 				}
 
-				for( final ItemStack fluixCrystalStack : materials.fluixCrystal().maybeStack( 2 ).asSet() )
+				materials.fluixCrystal().maybeStack( 2 ).ifPresent( is ->
 				{
-					final EntityItem entity = new EntityItem( this.worldObj, this.posX, this.posY, this.posZ, fluixCrystalStack );
+					final EntityItem entity = new EntityItem( this.worldObj, this.posX, this.posY, this.posZ, is );
 
 					this.worldObj.spawnEntityInWorld( entity );
-				}
+				} );
 
 				return true;
 			}