How to turn on cheats in minecraft java?

Regarding your question - how to turn on cheats in Minecraft java

On a multiplayer server:
To turn on cheats:
Type op  in the console.
Done.
To turn off cheats:
Type /drop 
Done.
On a singleplayer world:
To turn on cheats:
Using the built-in LAN server:
Pause the game.
Click on Open to LAN.
In the options, change Allow Cheats: false to true (click on it).
Open the server.
Changing your save file:
Close your world.
Using NBTEdit, open your save file (%AppData%/.minecraft/saves//save.dat)
Change the NBT node AllowCommands from 0 to 1.
Save and reopen the world.
To turn off cheats:
Using the built-in LAN server:
Note: This only works on players who connect to this world, not you.
Pause the game.
Click on Open to LAN.
In the options, change Allow Cheats: true to false (click on it, if it already displays Allow Cheats: false, obviously don't click).
Open the server.
Changing your save file:
Close your world.
Using NBTEdit, open your save file (%AppData%/.minecraft/saves//save.dat)
Change the NBT node AllowCommands from 1 to 0.

Save and reopen the world.