This doesn't exist in Minecraft, only for Mods and our Suggestions.
Hammers are both Weapons and Tools which is classified in the Miscellanous group. They can be obtained by crafting or killing a Mutant Zombie (Stone Hammer). You can even get them by killing Ogres.
They are used to be crafted like shovels but with the Block version of it.
They can be used to crush any Vegetable (Wheats, Carrots and Potatoes and gain them), Ice and Mobs. When crushing Ice, you can obtain it but water will flow and if it drops in the water and melt. It can be used to crush Mobs (especially Passive and Neutral Mobs (exept for Enderman) ).
- They are all used from Blocks to be crafted.