I would like to make a monster that attacks you physically flying, but the eclipse don't open the references classes, and researching on the internet just find codes from older versions and end up not working, and extending to EntityFlying can not set the caused damage...

 

My Ghost Class:

 

package mike.bathicraft.mob;

import mike.bathicraft.items.GerenciadorDeItems;
import net.minecraft.entity.SharedMonsterAttributes;
import net.minecraft.entity.ai.EntityAIAttackOnCollide;
import net.minecraft.entity.ai.EntityAIFleeSun;
import net.minecraft.entity.ai.EntityAIHurtByTarget;
import net.minecraft.entity.ai.EntityAINearestAttackableTarget;
import net.minecraft.entity.ai.EntityAIRestrictSun;
import net.minecraft.entity.ai.EntityAISwimming;
import net.minecraft.entity.ai.EntityAIWander;
import net.minecraft.entity.ai.EntityAIWatchClosest;
import net.minecraft.entity.monster.EntityMob;
import net.minecraft.entity.passive.EntityVillager;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.init.Blocks;
import net.minecraft.init.Items;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.util.ChunkCoordinates;
import net.minecraft.util.MathHelper;
import net.minecraft.world.World;

public class EntityFantasma extends EntityMob {

	public EntityFantasma(World world) {
		super(world);
		this.setSize(0.9F, 1.9F);
		this.experienceValue = 5;
		this.tasks.addTask(0, new EntityAISwimming(this));
        this.tasks.addTask(3, new EntityAIAttackOnCollide(this, EntityPlayer.class, 1.0D, true));	        
        this.tasks.addTask(7, new EntityAIWander(this, 1.0D));
        this.tasks.addTask(8, new EntityAIWatchClosest(this, EntityPlayer.class, 12.0F));
        this.targetTasks.addTask(1, new EntityAIHurtByTarget(this, true));
        this.targetTasks.addTask(2, new EntityAINearestAttackableTarget(this, EntityPlayer.class, 0, true));
	}

	  @Override
	    protected void applyEntityAttributes()
	    {
	        
	        super.applyEntityAttributes();
	        this.getEntityAttribute(SharedMonsterAttributes.attackDamage).setBaseValue(3.0D);
	        this.getEntityAttribute(SharedMonsterAttributes.followRange).setBaseValue(20.0D);
	        this.getEntityAttribute(SharedMonsterAttributes.movementSpeed).setBaseValue(0.4D);
	        this.getEntityAttribute(SharedMonsterAttributes.maxHealth).setBaseValue(15.0D);
	        
	    }
	  
		protected boolean isAIEnabled()
	    {
	        return true;
	    }
		 		 		  
		 protected Item getDropItem(){
				return Items.iron_ingot;
			}

			protected void dropRareDrop(int par1){
				switch (this.rand.nextInt(3)){

				case 0:
					this.dropItem(Items.iron_sword, 1);
				}
			}

			 public boolean doesEntityNotTriggerPressurePlate()
			    {
			        return true;
			    }

			 protected void updateFallState(double par1, boolean par3) {}

			 protected void fall(float par1) {}

			 protected boolean canTriggerWalking()
			    {
			        return false;
			    }


}

There are plenty of examples in vanilla code, like EntityBlaze and EntityGhast.