So, heres the code I have:

 

package tutorial;

import java.util.Set;

import com.google.common.collect.Multimap;
import com.google.common.collect.Sets;

import net.minecraft.block.Block;
import net.minecraft.block.state.IBlockState;
import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.entity.EntityLivingBase;
import net.minecraft.entity.ai.attributes.AttributeModifier;
import net.minecraft.init.Blocks;
import net.minecraft.inventory.EntityEquipmentSlot;
import net.minecraft.item.*;
import net.minecraft.util.math.BlockPos;
import net.minecraft.world.World;

public class MultiTool extends ItemTool {

private static final Set<Block> effectiveBlocks = Sets.newHashSet(new Block[] {Blocks.PLANKS, Blocks.BOOKSHELF, Blocks.LOG, Blocks.LOG2, Blocks.CHEST, Blocks.PUMPKIN, Blocks.LIT_PUMPKIN, Blocks.MELON_BLOCK, Blocks.LADDER, Blocks.WOODEN_BUTTON, Blocks.WOODEN_PRESSURE_PLATE, Blocks.ACTIVATOR_RAIL, Blocks.COAL_ORE, Blocks.COBBLESTONE, Blocks.DETECTOR_RAIL, Blocks.DIAMOND_BLOCK, Blocks.DIAMOND_ORE, Blocks.DOUBLE_STONE_SLAB, Blocks.GOLDEN_RAIL, Blocks.GOLD_BLOCK, Blocks.GOLD_ORE, Blocks.ICE, Blocks.IRON_BLOCK, Blocks.IRON_ORE, Blocks.LAPIS_BLOCK, Blocks.LAPIS_ORE, Blocks.LIT_REDSTONE_ORE, Blocks.MOSSY_COBBLESTONE, Blocks.NETHERRACK, Blocks.PACKED_ICE, Blocks.RAIL, Blocks.REDSTONE_ORE, Blocks.SANDSTONE, Blocks.RED_SANDSTONE, Blocks.STONE, Blocks.STONE_SLAB, Blocks.STONE_BUTTON, Blocks.STONE_PRESSURE_PLATE, Blocks.CLAY, Blocks.DIRT, Blocks.FARMLAND, Blocks.GRASS, Blocks.GRAVEL, Blocks.MYCELIUM, Blocks.SAND, Blocks.SNOW, Blocks.SNOW_LAYER, Blocks.SOUL_SAND, Blocks.GRASS_PATH});;

    protected MultiTool(ToolMaterial material)
    {
       super(10.0F, -2.8F, material, effectiveBlocks);
    }

public boolean canHarvestBlock(IBlockState blockIn){
	return true;	
}

public boolean onBlockisDestroyed(ItemStack stack, World worldIn, IBlockState state, BlockPos pos, EntityLivingBase entityLiving){
	BlockPos top = pos.up();
	BlockPos bottom = pos.down();

	worldIn.destroyBlock(top, true);
	worldIn.setBlockToAir(bottom);

	return true;
}


}

 

 

That is actually a tool that breaks every block, but I'm trying to make it break a 3x3 area. I know it may sound simple for some of you, but I just started modding yestarday, and although I have some java knowledge, I'm not the most skillfull programmer.

 

I'd really apreciate if any of you guys could give me a hint on how to do this.

(Sorry for the spelling mistakes I may have commited, English is not my main language)

If you mean like this then here you go and all credit to the ones who posted it.

 

http://www.minecraftforge.net/forum/index.php/topic,40887.0.html

The thing is, this should have replaced the bottom block and the top block with air, but it doesn't...

 

Atleast this part should've worked:

public boolean onBlockisDestroyed(ItemStack stack, World worldIn, IBlockState state, BlockPos pos, EntityLivingBase entityLiving){
	BlockPos top = pos.up();
	BlockPos bottom = pos.down();

	worldIn.destroyBlock(top, true);
	worldIn.setBlockToAir(bottom);

	return true;
}

I think I got the problem, I misspelled the method name   

Gonna try it now...

Got it to work, thanks for the help!

 

Heres the code, if anyone needs it:

public boolean onBlockDestroyed(ItemStack stack, World worldIn, IBlockState state, BlockPos pos, EntityLivingBase entityLiving){
	BlockPos top = pos.up();
	BlockPos bottom = pos.down();

	worldIn.destroyBlock(top, true);
	worldIn.setBlockToAir(bottom);

	return true;
}

Change the name to solved if you have solved it. Also happy that my thread was useful for over people to. On thing though, this wont work with enchantments, so do you want your multitool to be enchantable?

Another thing, your multitool wont be effective on modded blocks, take a look on my multitool:

http://pastebin.com/jFmqACY9