I have a hoplite type battlemaster tank with shield and spear. He has the Spear Mastery feat. I use the spear as my main melee weapon and have javelins for ranged attacks. What are the game mechanics for drawing and using a javelin while holding another weapon? Can I simply throw a javelin and somehow still have the spear at the ready on my round?
If I can’t, I was thinking of just carrying 2 spears, one for throwing and one for melee, or javelin and spear. How would that work game mechanics wise? What can I do in my one round of combat?
With a shield on one arm you only have one free hand unless you're a Thri-Kreen.
Battlemaster has "Quick Toss" which lets you throw a weapon as a bonus action and draw it in the same action.
Unless you're using the new DND One rules then dropping a weapon or held item (other than a shield) is generally considered a completely free action, not even requiring your free environment interaction to use (NOTE: This can vary with some DMs who don't like the antics and consider dropping your free environment interaction).
If you wish to always have your spear in hand then you can drop your spear, use the "quick toss" ability as a bonus action and pick your spear back up with your environment interaction. If you don't mind being without the spear off-turn then you can drop it, use an action to draw and throw your javelin, use your bonus action with "Quick Toss" to draw and throw another javelin, then wait until the next turn to pick up your spear or draw and throw more javelins.
If you don't mind carrying your javelin around, rather than the spear, you can open up with a javelin toss as your action and either draw another javelin or draw your spear. You could also use "quick toss" to throw a second javelin and draw another or throw the one in your hand, draw your spear and move to attack in melee.
Consider the circumstances you'll need the extra range of the javelin as well. Spear range is 20/60 and Javelin is 30/120. So the Javelin will only give you an extra 10' over the spear without disadvantage and then double the distance with disadvantage to hit. Most of the time you'll probably want the Javelin for the 120' range at disadvantage and you're unlikely to worry about combat if you're throwing for that range. With that in mind you would likely carry your spear most times to be at the ready with it. If you have an enemy at range you probably have time to spare for switching to javelin and if you don't you could always drop the spear to draw the javelin or use your environment interaction to stow your spear then quick toss to draw a javelin and throw it. Once you're in range to charge into combat you can switch back to the spear. If you are at closer range you likely want to toss the spear and draw another instead since you have +1 with the spear and the extra damage in the UA for the feat doesn't specify that it's melee damage only.
I suggest looking into the magic item "Efficient Quiver" as well. It would let you carry 6 spears and 18 javelins.
I have a hoplite type battlemaster tank with shield and spear. He has the Spear Mastery feat. I use the spear as my main melee weapon and have javelins for ranged attacks. What are the game mechanics for drawing and using a javelin while holding another weapon? Can I simply throw a javelin and somehow still have the spear at the ready on my round?
If I can’t, I was thinking of just carrying 2 spears, one for throwing and one for melee, or javelin and spear. How would that work game mechanics wise? What can I do in my one round of combat?
With a shield on one arm you only have one free hand unless you're a Thri-Kreen.
Battlemaster has "Quick Toss" which lets you throw a weapon as a bonus action and draw it in the same action.
Unless you're using the new DND One rules then dropping a weapon or held item (other than a shield) is generally considered a completely free action, not even requiring your free environment interaction to use (NOTE: This can vary with some DMs who don't like the antics and consider dropping your free environment interaction).
If you wish to always have your spear in hand then you can drop your spear, use the "quick toss" ability as a bonus action and pick your spear back up with your environment interaction. If you don't mind being without the spear off-turn then you can drop it, use an action to draw and throw your javelin, use your bonus action with "Quick Toss" to draw and throw another javelin, then wait until the next turn to pick up your spear or draw and throw more javelins.
If you don't mind carrying your javelin around, rather than the spear, you can open up with a javelin toss as your action and either draw another javelin or draw your spear. You could also use "quick toss" to throw a second javelin and draw another or throw the one in your hand, draw your spear and move to attack in melee.
Consider the circumstances you'll need the extra range of the javelin as well. Spear range is 20/60 and Javelin is 30/120. So the Javelin will only give you an extra 10' over the spear without disadvantage and then double the distance with disadvantage to hit. Most of the time you'll probably want the Javelin for the 120' range at disadvantage and you're unlikely to worry about combat if you're throwing for that range. With that in mind you would likely carry your spear most times to be at the ready with it. If you have an enemy at range you probably have time to spare for switching to javelin and if you don't you could always drop the spear to draw the javelin or use your environment interaction to stow your spear then quick toss to draw a javelin and throw it. Once you're in range to charge into combat you can switch back to the spear. If you are at closer range you likely want to toss the spear and draw another instead since you have +1 with the spear and the extra damage in the UA for the feat doesn't specify that it's melee damage only.
I suggest looking into the magic item "Efficient Quiver" as well. It would let you carry 6 spears and 18 javelins.