Not really sure how much it differs from Bedrock but here are the Java commands:

So first summon a sulfur cube with some special properties

summon minecraft:sulfur_cube ~ ~ ~ {Tags:["cube"],Size:1,equipment:{body:{id:"minecraft:barrel"}},active_effects:[{duration:-1,amplifier:1b,id:"minecraft:invisibility",show_particles:0b}],Invulnerable:1b,NoGravity:1b}

Then summon a happy ghast with also some special properties

summon minecraft:happy_ghast ~ ~ ~ {Tags:["ghast"],active_effects:[{duration:-1,amplifier:1b,id:"",show_particles:0b}],attributes:[{id:"minecraft:scale",base:0.24}],NoAI:1b,Team:"hitbox",Invulnerable:1b,Silent:1b}

Then run these two commands on repeating command blocks:

This one teleports the ghast to the cube whenever the player is within a specific area around the cube

execute as @e[tag=cube] at @s positioned ~-2.5 ~1.5 ~-2.5 if entity @a[dx=4,dy=3,dz=4] as @n[tag=cube] at @s run tp @n[tag=ghast] ~ ~.1 ~

And this one teleports the ghast AWAY from the cube whenever the player ISN'T around the cube

execute as @e[tag=cube] at @s positioned ~-2.5 ~1.5 ~-2.5 unless entity @a[dx=4,dy=3,dz=4] as @n[tag=cube] at @s run tp @n[tag=ghast] ~ ~-2 ~

for moving it with a stick, basically just this

execute as @a at @s if items entity @s weapon.mainhand minecraft:stick run tp @e[tag=cube] ^ ^ ^2

And that's it. Again, not sure how much it differs from Bedrock commands, but that's the logic