You know how in Minecraft, the World is ever-expanding and all the biomes are randomized?

My generalized question is: In relation to a space simulation that is also ever-expanding as the player moves about the world, how would one go about programming this randomization in Java?

My real question is: Could I get a simplified example broken down into these example classes:

• astroids (This would include how many astroids there are, their positioning in space, their size, how often the larger astroids occur, how close they are to each other, the limitations of how many of the large asteroids can be in one field, how often astroid fields are generated, etc.)
• star-types (size, color, type, how often they occur, where hey occur, etc.)
• inhabitable-planets (size, positioning, how often they're generated, where they are generated, etc.)

This would be very helpful currently since I wish to make a simplified version of such a program.