Java out of memory /game crashed when initializing

Whenever I try to load the game by pressing play on the launcher, the launcher loads like normal but then reopens with a crash report showing. it says
"The game crashed whilst initializing game
Error: java.lang.OutOfMemoryError: Java heap space"
I have looked up how to fix it but none have worked? I'm not sure how to fix it and do not want to switch to the Windows 10 version of Minecraft